Barnschop's Life

3 phase Cage Induction Motor go/no go testing

2009-05-15T23:10:00.003Z

How to quickly test a new three phase motor.

Many electricians have never had to determine whether a three phase motor is faulty since the majority of their work is involved with single phase work. The same can also apply to electrical apprentices since this may not have been taught.
There is nothing worse than removing an old motor to replace it with what turns out to be a faulty motor. There are some basic tests that can be carried out to try an minimise the risk of putting faulty three motors into service.

The tests below should be done prior to installation.

Test one is to verify that the shaft is free to turn and that the fan is not catching the cowl. Spinning the shaft should identify siezed bearings by listening for noises in addition to the ease at which the shaft can be turned.

Test two is to verify that all three phases are in balance. More often than not the motor will be already connected in either star or delta configuration and thus terminals UVW should be tested using an ohmmeter. U-V, U-W, and V-W should all give the same value of resistance across them. Where the motor is to be employed with a star/delta starter then the three individual coils can be tested and again should be the same.

Test three involves an insulation test of the phases to earth. Although if configured in either star or delta the three separate windings will be connected together you will see most time served electricians still test each terminal ie. U V and W to earth.

You should notice that the three simple tests outlined above will not in all cases identify faults with a new motor.

Do also investigate any anomalies in the tests above since it might be something that is simple to cure and you will not be looked upon in a good light if you condemn the new motor and increase production losses.

Transducers Part 4 - ultrasonics

2009-05-13T13:47:00.003Z

Hello, is the common shout by many to see if they get an echo coming back from an object or objects. The action of shouting of hello creates vibrations of the air that travel outwards much like the action of a pebble dropped into a pool of water. If the tiny ripples of water created by the pebble hit a solid object then they change direction much like light hitting a mirror. Sound waves produce a similar effect and that is what we call an echo.

Sound is a name of vibrations that we can actually hear, whereas much higher vibrations we perceive as visible light. So there is an whole spectrum between sound we hear and the light we see. The name given to vibrations that are just above most human hearing is called ultrasonic.

No doubt your mind will have already used neural pathways to bring up how bats use ultrasonics to avoid objects and some of you may also be picturing the scan of you before you were born.

The piezoelectric effect is used for the transmitter and receiver. In the simplest form an ultrasonic frequency is sent in short bursts, then the echo received by the same sensor. Electronics are used to measure the time taken for the pulses to return. The time taken being proportional to distance between the sensor and the object reflecting the ultrasonic frequency back.

Ultrasonic transducers are not just used for distance measurments as later blogs will show

Transducer Part 3 - The Piezo-electric Effect

2009-05-13T12:50:00.003Z

Piezo is derived from Greek and means to squeeze. Certain materials that are squeezed or stressed will produce a voltage that is proportional to the level stress applied. Then again your lecturer should have told you all this. All I am doing is drilling through the brain to lay down even more neural interlinks. Although many materials exhibit the piezoelectric effect most common is Quartz crystal.
Another important point is that if a voltage is applied to a piezoelectric effect material it will stress. The effect is therefore reversible and this should be noted since piezoelectric is used in transducers that convert energy into electricity or vice-versa.

If we take a diaphragm and connect to it some piezo material and subject the arrangement to air that is vibrating then electrical voltages are produced proportional to the amplitude of the vibrations. This arrangement you might know better as a microphone. Equally we could with slightly modifications to the design, namely in size, make a device that will vibrate the air in proportion to a varying electrical signal, yes, a loudspeaker.

The air is not the only thing that vibrates since there is also vibration in the earth caused by earthquakes but I doubt many electrical apprentices will get involved with those. Some though will come across devices in industry that measure the vibration of machinery. By processing the vibrations generated by machines with computers it becomes possible to identify failure in components long before total failure occurs.

You are reading this text via a computer that I entered via a computer. Tick tock, tick tock, goes the clock. No I have not lost my reasoning since the piezo electric effect is used both in computers and in certain clocks that you know as quartz clocks. Most objects will have a frequency at which they will vibrate naturally at, this is called the resonant frequency. Quartz crystal is no different, so by differing the dimensions of the crystal you achieve a different resonant frequency.

There are many more applications of the piezoelectric effect used in transducers and sensors so look for blog entries for more later

Transducer Part 2 - The Strain Gauge

2009-05-13T05:35:00.008Z

I have chosen the strain gauge to start with since it uses some of the basic electrical principles that are taught to electrical students. Problem is that for many the theory will have been lost in some obscure part of the brain. Therefore it is time to trigger new neural pathways to this long forgotten collection of brain cells.

Before getting into the theory it was mentioned that a piece of knicker elastic can help understand strain gauges in Part 1 of transducers. With your knicker elastic or even rubber band in both hands, pull at either end. You will notice the the width of knicker elastic becomes thinner the more it is stretched.
No doubt the above demonstration will have triggered the eureka moment for many students of electricity into how the strain gauge works. I say farewell to those for whom the penny as dropped and continue on for the others.

Put these in order of lowest resistance, a 1 metre diameter of copper cable a meter long, 1 metre diameter of copper cable 10 metres long, 1 millimetre diameter of copper cable a meter long, or a 1 millimetre diameter of copper cable 10 metres long.

Did you get:-

metre diameter of copper cable a meter long,
metre diameter of copper cable 10 metres long,
millimetre diameter of copper cable a meter long,
millimetre diameter of copper cable 10 metres long.

So for the same material the resistance is proportional to both it's cross sectional area and length. Those neural pathways are now being formed, I can sense it.

Back to the knicker elastic in which when pulled gets longer and narrower (the csa reduces). Copper does have a very very tiny amount of stretch property like the elastic but so small you are unlikly to notice it, however as with the knicker elastic the more it is stretched the longer in becomes increasing the resistance and the less csa so again increasing the resistance. Once released the resistance returns back to its previous value.

The actual strain gauge that uses copper or another metal will be either a wire looped and bonded onto an insulated material or metal foil again bonded to a non metalic surface.

So hopefully you will now have the gap between your knowledge bridged with neural network links from basic theory of resistance to strain gauges and thus transducers.

Rather than filling up your head with more information about strain gauges at this point I will return later in another blog.

Electrical Transducers Part 1

2009-05-13T04:58:00.005Z

This is again another blog entry to give electrical apprentice the link between the theoretical world taught at technical college and the practical world in which a few will be working in.

So what is a transducer?

Your lecturers will no doubt give you the answer that a transducer is a device that converts one form of energy into that of another. For the electrical apprentice this either means converting from or to electrical energy from another source of energy.

For many electrical apprentices that may later work in industry it is important to understand how transducer devices work, since having this knowledge may help to understand the operation of a particular process or machine. Knowing a process or machine operation is a key to effective diagnosis. Later I intent to, at a later date write a blog on fault diagnosis.

With so many different transducers available I thought I had better split the topic up into many different blogs so that you will not have to search through loads and loads of words on a single page.

Where I can think of an analogy, this will be included so as to assist in the explaination a specific transducer. I always find that electricity, because it cannot be seen is best explained using something more familar that is visible or at least easier to understand.
For example, what happens when you slowly close a tap/faucet on a water pipe? The action of closing the tap causes resistance to the flow of water, thus the flow slows down, eventually stopping. The tap/or faucet can therfeore be likened to the variable resistor found in electrical circuits in that it too offer resistance but this time to the flow of electricity and not water.

In part 2 I am going to be looking at knicker elastic and strain gauges.

Variable Speed Drives or AC Inverters

2009-05-11T06:42:00.004Z

Variable Speed Drives or AC Inverters are a common subject that I get questions asked by apprentices and thus thought I might tell others in my words how these are used in an easy and fairly non technical way.

50HZ (60Hz in the US) is the cycles per second of the mains frequency which most apprentices can tell me. Now we look at a 3 phase squirrel cage induction motor which reveals that it will rotate at a given speed. The fastest motor speed found by the apprentice in the UK will be slightly less than 3000 rpm. So the formula is given N (rpm) = f * 60/P where f is frequency in hertz and P is the pair of poles.

So now asking the apprentice what we can change to alter the speed they are most likely to answer either the pair of poles or the frequency and both are correct. Pole change motors are possible but not very practical and are expensive so we are left with changing frequency.

The black box is now brought into play since it is best at this stage to only give the the very basics. Three phases go into the box and another three come out and then we add a speed control potentiometer. Explained is that the mains three phase frequency is now converted to a different frequency. Now many apprentices at this stage begin to ask what is inside the box since it is a little bit simplistic.

So now the black box is opened so to speak and on the drawing additional boxes are drawn. First there is a rectifier a storage capacitor and a box marked chopper. At the stage of asking about speed control most apprentices will understand how the rectification of AC into DC takes place and also how a capacitor can store electricity. The chopper box internals may or not be understood by some. However the simple explanation is that it chops up the DC to produce AC.

It is at this stage that most will accept the explanation of the basic of how inverters or Variable Speed Drives work?

Basic Three Phase AC Theory Understanding

2009-05-11T05:44:00.003Z

Another subject that often baffles electrical apprentices is in the use of three phase AC. At technical college they are given the theory and little else by the lecturers. Confusion thus remains which can for some inhibit or at least slow down further learning on the subject.

Now at this point I have to mention that most of my experience is in industry and thus these apprentices are likely to be familar with the equipment found there. For those of you reading this that wishing to gain a better understanding I should point out that electrical motors form most of the direct use of three phase AC since lighting is single phase.

I ask the apprentice to demonstrate their understanding of single phase AC by having them draw the sinusodial waveform. I then see if they can draw the three phase sinusodial waveforms which hopefully they can and show that there is a 120 degree displacement between the three. Most have no problem in drawing out the waveform. A question is asked to the apprentice "When one phase is at a maximum in the postive direction what is the value of the other two at that instant." With a little bit of help they point out or can see that this happens

With two magnets it is demonstrated for the purpose of refreshing their knowlegde that two like poles repel each other and that two differing poles attract each other. From this I draw a circle and put on three windings and in the centre is a magnet. I then ask them to look at the waveform and show the direction on the circle that each phase would become postive. I then ask them what happens with the magnet and most indicate that this would turn in the direction that they indicated on the circle.
Have you ever seem the light bulb on someones head glow bright because for most apprentices in my experience it is at this moment that you can almost hear them shout "Eureka".

Silence and now AC

2009-05-11T04:41:00.004Z

How does AC electricity work?

A few apprentices have over time have asked me to explain how AC works, since they comprehend how DC works. They know that you need a flow of electrons around circuit which is sent from the negative terminal of a battery and returns to the positive terminal. They know that these electrons are capable of heating up metal to such an intensity that it produces visible light. Again they also know that the heated metal is found inside light bulbs.

So when asked about AC they know that electrons flow first in one direction and then all goes in reverse and the electrons flow in the opposite direction etc. The problem is that they cannot understand how the circuit is made.

In order to explain how AC works I have then asked them to look at the old fashioned steam train and how the piston moves backwards and forwards and yet creates a movement in one direction. The piston pushes out and turns the wheel, as it pulls back it continues to turn the wheel in the same direction.

So once they understand how a backwards and forward motion can be converted to a movement only in one direction, it is then time to look at railways again. So we now look at a super long train and a big powerful locomotive at one end. The locomotive will only move a few yards in either direction however.

I then point out that it is not the content of the wagons making up the train that is important it is the actual movement backwards and forwards that is important. A secondary reason for using the train is to explain how the relatively slow electron can create electricity at the speed of light. When the locomotive shunts into the trucks/wagons you can hear each collosion as the wagon/truck hits the next and so on. Imagine how long it would take from the first truck/wagon being shunted until the last one gets shunted. Even if the train went from the UK to the USA, it would not take long before a shunt in the UK would be heard in the US.

The apprentice can now translate the locomotive and associated train into electron flow in an electrical circuit and how their backward and forward movement can still produce a linear effect.

17th Edition IEE Wiring Regulations (BS7671:2008)

2008-02-12T02:27:00.000Z

£65 or 10 years in prison, your choice.

The new 17th Edition of the Requirements for Electrical Installations is now available to purchase from your normal sources such as AmazonUK, the price, well that is £65, although you can get secondhand cheaper.

IEE Wiring Regulations 17th Edition : (BS 7671: 2008) (Paperback)

I had to admit to having a smile on my face when reading the reviews at Amazon though. Especially in how it can increase your pulling power. Strange though it may seem, it could make sure that if you read and obey you will have liberty and freedom to chase the girls (or boys). Failure to comply could well result in a manslaughter charge and if found guilty (remembering you have to prove your innocence) could face a lengthy prison sentence. To reiterate, The Electricity At Work Regulations, regulation 29 is a clever bit of law that puts the onus on you to prove you took all reasonable steps. In order prove you took reasonable steps then it would be in your defence that your work complied with that contained in the Red Book or 17th Edition Wiring Regulations BS7671:2008. £65 or 10 years in prison, your choice.

A time to die

2007-11-18T08:38:00.000Z

There is a time for us to die and I have been working on a website called A Time To Die. The aim of the website is to give your advice and hints so that you have everything in place ready for your death. This may be writing a will or making sure you have sufficient funds or life insurance to cover your burial needs.

My friend Chris said that since she is struggling at the moment why should she bother since she would not be here, so a paupers grave would suffice. I took on her point and later discovered that if you have children you can put in your will who you would like your parental responsibility passing to. Although this can be challenged it is there never the less.

Chris went on further to then suggest that she had no plans of dying just yet. To this I had to reply that I had two uncles that were taken early.

What got me started on the website in the first place was that an elderly aunt began to suffer with Alzheimer's disease and Dementia and although she had written a Last Will and Testament, she had not be advised to make out a Power of Attorney. Her estate did not really amount to much but the problems encountered trying to administer her affairs seemed to be insurmountable. Although we managed in the end, being given the POA would have made it far simpler.

If you have had problems similar to those encountered to those mentioned above, why not comment and perhaps I can make use of the information

Remember A Time To Die

Friday Boiler Course

2007-10-14T05:49:00.000Z

Attended a course on steam boilers that did not really cover much more that we knew already.

The sight glass proving method as altered though. For those not in the know, sight glasses are situated on the side of the boiler and tell you how much water is in the boiler. Too little and the boiler can be potentially a bomb just getting ready to explode.

There are three handles or taps on the sight glasses which should all be facing downhill, this gives a quick visual indication that they are set correctly for normal operation. The top is the steam valve, middle is the water valve, and finally the bottom is the drain valve.

New gauge glass procedure is now

steam valve - closed- horizontal
water valve - closed- horizontal
drain valve - open - horizontal

gauge should empty and after initial blast should stop indicating that steam and water valves are holding

Opening and then closing the steam valve will wash the steam line and you shoulkd see shimmers as steam passes through.

Opening and closing the water valve will wash the water line and you should the level rise in the sight/gauge glass.

Close the drain cock, slowly open the water cock, sight glass should fill up, slowly open the steam cock and the water level should slowly drop to match the actual boiler level.

Have a look at the Spirax Sarco website for more on steam boilers

2391 Theory passed

2007-10-14T05:31:00.000Z

Just thought I would let you all know I have passed the theory side of C&G 2391 Inspection and testing. It is now down to the practical and then yet another qualification.
Going on a defribrulator course on Monday so will let you know how that goes.
Been adding some more content to http://www.pullthegirls.co.uk in respect of online dating.
Going to try and get some Autumn photographs too, these will show the colours of Autumn leaves.

An end of Split Consumer Boards??

2007-10-12T13:19:00.001Z

The draft addition of the 17th Edition, BS7671:2008 contains new requirements for bathrooms. All circuits will need to be protected by 30mA RCD so this would mean the lights.

If you look at the logic, what would be the point in having a split consumer unit just for lighting circuits that are not supplying bathrooms or outside lighting?

Welcome any comments on this

Monday, Interview

2007-10-12T13:09:00.000Z

Went for an interview for a tutoring post with respect to the 17th Edition or BS7671:2008. Everyone that knows me thought I would have no difficulty in obtaining the post. I had been on nights and with traffic and getting into the place made me late. Not a good start to the interview, being tired did not help with coming up with suitable answers to the questions either.

On Wednesday I had a feeling that all had not gone well and sure enough I got a phone call saying that I had not been successful. Still even though I cannot tutor people and get paid for it. I can still try and help on here by offering advice on the 17th Edition.

Making money online

2007-10-03T12:31:00.000Z

Making money from the Internet?

The easy way.

Now with no more than a fundamental knowledge of typical word processor usage you too can be earning cash.

To start with you need to sign up for a blog yourself. What is your interests in life, you maybe surprised at how many others have the same interests.

Do not consider Adult Material since this will limit returns or even prevent you from getting accepted.

I can show and assist in helping you to get the most from your blog in terms of revenue. Once you have got your blog set up and a number of postings, leave a comment with the address of your blog. I will leave a link for the next move.

Listen I am doing this to make money, I take no money from you though so do not worry.

How much money is like asking how long is a piece of string. Depends on too many variables to go into here. Suffice to say I will try and get you the most for 6 months.

17th Edition Wiring Regulations

2007-10-01T07:37:00.000Z

In 2008 the 17th Edition of the wiring regulations that are now called BS7671 will come into force.

The final copy is not available yet, but a draft was made avaialble for public comment. Let us look at some alterations between the draft and the present 16th Edition

In the draft it appears that the layout of the regulations follows the International Electrotechnical Commission’s (IEC) numbering system, this means that Part 6 and Part 7 are reversed.

Part 1 additions are protection against voltage disturbances and protection against electromagnetic influences

Part 2 includes some new and changed definitions

Part 4 includes several significantly changes, remember direct contact and indirect contact, these are now basic protection and fault protection respectively. A lot of jiggling with this part as taken place. Supplementry protection with the use of RCD comes under the heading of additional protection.

With the normalised voltage for the UK having changed to 230Volts the earth fault impedances shown in the tables are different.

More to come later

C&G 2391-101 July 2007 Exams

2007-07-27T00:19:00.000Z

I am going to put the questions in my own way but the answers will be the same as those for the exam.

1. What are the three main area to be verified on a new installation?

These would be equipment and material complies with relevant British Standard - all parts are correctly selected and erected - no parts are visibily damaged or defective

2. Ignoring compliance with BS 7671, earthing arrangement and load capacity what else must the designer must ensure when the work is not a new installation?

3. Give three locations that could have to comply to other statutory regulations other than the EAWR.

Approved Document Part P is a statutory document and thus dwellings
Locations that have explosive atmospheres other than Mines and Quarries
Cinemas

4. Give an example of each of the following
Limitation of discharge of energy Electric fence used on farms
Placing out of reach Pickups on electric cranes or overhead wires
Undervoltage Protective Devices Motor controllers

5. (i) What statutory document places a duty on person carrying out inspection and testing Electricity At Work Regulations 1989.
(ii) Which two groups of people does the the inspector have a duty to ensure safety of? Although worded confusingly I think himself and others.

6. What instrument should be used to carry out a continuity test of a circuit protective conductor? Low resistance ohmmeter typically with a digital instrument having a 0.01 ohm resolution
What would be unit of measurement of the above instrument? Ohms
Why would the above instrument and scale be selected? The instrument would be need to be able to measure the low resistance encountered with this kind of test

7. On a TT system which would be the first three live tests to be carried out?
Earth Electrode Resistance
Earth fault loop impedance Ze
Prospective fault current

8. Give correct names for three protective conductors that maybe connected to the MET
Main earthing conductor
Main equipotential bonding conductors
Circuit Protective Conductors

9. A cable have a resistance of 0.183 ohms is 25m in length. What be the resistance if
you had 50m of the same cable 0.366
25m in length but twice the csa 0.0915
25m in length but with half the csa 0.366

10. What are the three reasons for carrying out the ring final circuit test

Continuity of the phase, neutral, protective conductor around the ring. That no interconnections exist. Correct wiring of the ring.

11. Assuming a circuit is safely isolated give three checks to be made prior to carrying out an insulation test.

12. Excluding saunas, bathrooms, and swimming pools, name three other special locations
Construction sites.
Caravan Parks
Agricultral and horticultral sites

13. International Protection rating consists of two numbers, what do the numbers represent
The first letter
The second letter
If an X replaces a number, what would that mean
The first letter signifys protection against ingress of solids eg IP4X 1mm
The second letter signifys protection against ingree of liquids.
Where the X replaces a number it means that the protection as not been checked or that it is irrelevant.

14. When polarity testing as part of initial inspection and testing is being carried out, what are the two stages that shold be carried out. Secondly which instrument would be used?

15. External to an electrical installation what are the component parts of the earth fault impedance for a a TT system.
Even though the question does not specifically request a drawing it does help with the explanation. At the consumer Phase conductor -Main earthing conductor -Earth electrode to General Mass of Earth. At the Distributor, General Mass of earth - Earth Electrode - Main earthing conductor - Neutral on Transformer Secondary.

16. Before an installation is powered up, Zs needs to be obtained. What test value needs to be used. What else is required to be known. Finally write out the formula
Test value is (R1+R), this is CPC + phase conductor resistance)
External earth loop impedance Ze would need to be known
Zs = Ze + (R1+R2)

17. What two methods could be used to ensure the measured value of Zs complies with BS 7671.
What is the maximum accepted value for tabulated values in BS 7671 of 0.35 and 14.1
Where the ambient temperature is known then a compensation factor can be used to determine the maximum value of Zs.
The Rule of thumb is used and is the worst case scenario and reduces values in BS7671 by 75%.
Using rule of thumb
0.35 would be 0.35 * 0.75 = 0.2625 ohms
14.1 would be 14.1 *0.75 = 10.575 ohms

18. A 30mA is required to have three instrument test applied. What are they and what currents would need to be applied.
At 50% of 30mA, 15mA the RCD should not trip
At 100% of 30mA, or 30mA the RCD whould trip in under 200mS
At 500% of 30mA or 150mA the RCD should trip in under 40mS

19. What are the two types of fault current measured at source, which needs to be recorded.
PEFC and PSCC
The largest of the two needs to be recorded

20. Why is prospective fault current important in selection of protective devices?
PFC is important since the protective device would need to be able to break the fault current under short circuit conditions

For questions 21 to 26 I am going to assume you have already have access to the exam paper.

21a Electrical Installation Certificate which would include a schedule of inspection and schedule of test results.
21b The designer
21c Usage and external influences
21d BS 7671, Guidance Note 3, GS38 are all non statutory, Electricity at work regulations is a statutory document
21e Confirm that the installation adheres to the requirements of BS 7671 and that there is no visible damage to the installation
21f Earthing Arrangement - Number and type of live conductors - Nature of Supply parameters - Supply protective device characteristics

22a Although the question is perhaps a little vague I beleive the answer is that since the buildings are attached, the new services would need to be taken to the main earthing terminal

22b

Circuit verified dead using method outlined in GS38
CPC disconnected at main DB and shorted to the phase conductor
At the new DB a low resistance ohmmeter is connected to the phase and disconnected CPC.
The value obtained is (R1+R2)

22c We have 30 metres of 25mm csa cable, given that the milliohm/ metre is 0.727 then (R1+R2) will be 2*25*0.727/1000 which is 0.03635 ohms. Zs is Ze+(R1+R2) from information Ze is 0.1 ohm therefore
Zs= 0.1 + 0.3635 ohms
Zs = 0.4635 ohms

22d The SWA would be glanded at both ends and this would mean that the resistance of the armourings would be in parallel with the CPC resulting a lower value of Zs.

23a You would need the three drawings given in GN3 or similar to explain the three stages of the test since this is a ring final circuit.

The phase and neutral conductor loop values are 40*7.41/1000 using the equation used above, thus giving 0.2964 ohms

The CPC is 40*12.1/1000 or 0.484 ohms

So taking the three loop tests we would PR1 to PR2 (PR) and NR1 to NR2 (NR) as 0.2964 and CPCR1 to CPCR2 (CPCR) being 0.484 ohms

Stage two requires that PR1 is connected to NR2 and PR2 is connected to NR1.

At each socket the value expected is (PR + NR)/4

(0.2964+0.2964)/4 = 0.1482 ohms

Stage three consists of PR1 being connected to CPC2 and PR2 being connected to CPC1

At each socket the value expected this time is (PR + CPCR)/4

(0.2964+0.484)/4 = 0.1951 ohms.

24a Precautions could be removing loads from the circuits such as lamps, being aware that the test voltage could cause damage to some electronic equipment and taking action like linking the phase and neutral conductors together.

24b Factors are the conditions of the individual circuits being tested, since the circuits are in parallel the value of the test will be less than that of the lowest test that would be obtained on individual circuits.

24c The test voltage needs to be 500 Volts. A test result lower than 2 Megohms would require further investigation although the minimum accepted result is 0.5 Megohms.

24d 1/Rt = 1/R1 +1/R2 etc

Since there are 14 circuits with values of minimum 200 Megohms. 1/Rt = 14/200 therfore

Rt = 200/14 Mohms.

= 14.2857 Mohms.

25a and b Circuit 10 is 80 metres using 1.5 mm T&E so CPC will have a csa of 1 mm. The maximum Zs is 4.8 ohms.

The Phase conductor (R1) resistance will be 80*12.1/1000 = 0.968 ohms using values in figure 2.
The Neutral conductor (R2) resistance will be 80*18.1/1000 = 1.448 ohms

Zs = Zdb + (R1+R2) where Zdb is earth loop impedance of new distribution board which from question 22 is 0.4635 ohms .

Zs = 0.4635 + (0.968+1.448)

Zs = 2.8795 ohms

Using the 3/4 rule of thumb maximun Zs value becomes 4.8 *3 /4 = 3.6 ohms

The value of Zs would be acceptable.

(Hard to believe that only 6 marks have been awarded for all that work and why did it require reference to a previous result)

25c A drawing here will assist to explain the procedure

At the furthest point of the circuit with all switches closed connect the earth loop impedance tester to the CPC and then the connect the other lead to the phase conductor, remembering that this is a live test and the risk needs to assessed. The result obtained will be Zs for the circuit. If the circuit was a two or more way arrangement, each way would need to be tested and the highest value would be recorded as the Zs.

26a. The basic drawing can be found in the On-Site Guide. TN-C-S would mean that the neutral and earth would be seperated in the distributors metering at the consumers end. The circuit would also include the main protection device, the protection device for the new DB and also the 20A MCB feeding the air curtain (Just what is an air curtain, not exactly common and therefore likely to create a problem to those taking the exam, IMHO).

26b. PEFC is given by Uo/Ze for the source thus PEFC = 230/.1 = 2.3kA

26c. Since Zdb is higher than Ze it can be assumed that the PEFC will be less than at the source.

26d. For this question we could say refer to question 20 since for me the answer is the same. This time the mark is not 1 but 2 however.

The PFC is important in selection of protective devices since this is the current that the device will need to break in case of a fault of negligible resistance.

These are the answers I have since worked out or found since taking the exam and although many seem to be similar I cannot be certain

I you disagree with the answers please add a comment

What is PART P?

2007-07-26T12:51:00.000Z

The Building Act 1984 in section(1)1 made provisions that regulations maybe made for various purposes. This meant that rather than going to parliment each time additions were needed, the Secretary of State can approve documents. Approved Document P: Electrical safety - 2006 edition is one of these documents, and is commonly referred to as Part P.

Prior to the introduction of Part P, anyone could install electrical equipment into a dwelling. The IEE did have regulations in place in the form of BS 7671, but these were not statutory and were often ignored by some installers (including DIYers). Part P does not limit who can install electrical equipment but does require that certain work will require prior notification to a building control body. There is an exception and that is where the installer is registered with an electrical self-certification scheme.

IT earthing arrangement, where used.

2007-07-24T09:59:00.000Z

Coal mining is one of the places that use an IT earthing arrangement.
Transformers used underground are of a Delta/Star arrangement, namely DY11. The transformer secondary star point is not connected directly to earth but through a current limiting impedance device.
The secondary side goes through a breaker that from memory contains a protection device that would trip if the resistance to earth drops below 20000ohms. Since the transformed supply could be used to supply a number of different parts of the mine called sections. Each section needs to be protected to afford discrimination and this means that insted of 20 k ohms the value is raised to 40 k ohms. Where final circuits are involved then a value of 60K would create a trip of the protective devices. Notice I said all the protective devices.

From memory three resistors are used to create a false neutral which in turn is connected to earth via another resistor. Should an earth fault on any of the circuits fed from the transformer occur then every one of the protective devices would have a voltage drop across the resistor connecting earth to the false star points. This voltage drop is sensed by electronics and causes the protective device to operate.

Prior to the arrangement above a core balance transformer was used. Each phase would go through the core or ring and thus each in turn would set up a magnetic field in the core. Since the current flowing in the three phases would under conditions be balanced, each magnetic field would cancel out the others thus giving no overall net magnetic field.
Under a fault condition there would be an overall magnetic field due to the imbalance and a this would cause a current to flow in a coil wrapped around the core. This current is sensed and would cause the protective device to operate.

C&G 2391-101 July 2007

2007-07-24T08:48:00.000Z

Well the 19 July 2007 finally arrived which for me meant at 18:30 I began the City and Guild's 2391-101 examinination.

The room was full of candidates sitting the exam, of those that took the course with me only one was missing.

Having completed the passed papers with relative ease, I did not feel under pressure, that was until I actually turned the paper over.

The first 20 questions took me one hour to complete. The second 6 questions took 90 minutes to complete. So the two and a half hour exam took that long for me and all the others but for a small minority.

Although the questions were in a similar vane to those I had practised with, the actual wording meant that for me at least, two or more possible answers could have been given.

The scenario for Part B was a Public house extension. Two questions involved an air curtain. (I have since found out that an air curtain is the name for the heating device fitted over many shop doorways.) This led to a little bit of a stall, since I had to try and think what one was.

Question 20 and 26 seemed to both ask the same question and I had to check back through the question paper to verify I had not made a mistake.

Why is PFC prospective fault current important in selection of a protective device? Okay the answer is easy. The protective device needs to be of a sufficient rating to break this current without substaining damage. The other part was easy too, which would need to be recorded the PSCC or PEFC. The answer is the highest since it is this current that determines rating required.

The DB was 20 Way with 14 ways used, the individual circuits tested at >200Mohms. What would the overall test be.

so 1/Rt = 14/R ; 1/Rt= 0.07Mohms

Thus we have 14.286 Mohm.

Perhaps the longest question to answer was on the ring final circuit test showing calculations.

You were given the loop length of I believe 40 Metres. A table gave resistance per metre length of all the csas used in the new installation.
So for 2.5mm this was 7.41 and for 1.5mm 12.1.

So for stage 1 you would have 40*7.41/1000 for phase and neutral conductors. The CPC would be 40*12.1/1000.
So PHr and Nr would both be 0.2964 while the cpc would be 0.484 ohms.

Stage 2 would be (Phr+Nr)/4 ; (0.2964+0.2964)/4 = 0.1482 ohms

while Stage 3 would give (PHr + CPCr)/4 ; (0.2964 + 0.484)/4 =0.1951 ohms

In addition to the calculation you also had to go through the procedure to conduct the 3 stages.

C&G 2391 Inspection and Testing Lighting?

2007-07-17T12:00:00.000Z

Many questions seem to include either a PIR or else discharge lighting. From this I have come to the conclusion that the person setting the question is wanting an insulation test to indicate that the phase and neutral need connecting together to prevent damage.
Discharge lighting generally have a choke to limit the current flow, this creates a reactive component which is reduced by fitting of a capacitor. If you check the rating of capacitors fitted they are normally rated at 250Volts. Testing with a 500Volt insulation resistance meter could damage the capacitor.
PIRs in a circuit contain electronics so should not be tested phase to neutral.

So how would you do an insulation test on a lighting circuit?

Disconnect circuit from supply and verify circuit is dead using approved method outlined in GS38
Check that the testing will not create danger to persons, livestock or property
Link together the phase and neutral
Check your instrument or it's leads are not damaged.
Select 500 Volt.
Securely clip one lead to the earth bar
Prove connection by testing to another earth terminal, this should show 0.0 megohms or short circuit
Clip to the phase/neutral connection and press test, wait for a steady reading and record.
Allow the instrument to remain connected to discharge any stored charge created by the test.
If test is greater than 2 Meg ohms, disconnect leads, reconnect phase and neutrals back into respective places, restore power.
Tests of under 2 Megohms would need further investigation but is not a fail as this is below 0.5 Mohms.

C&G 2391 Inspection and Testing EIC, PIR, MEIWC

2007-07-17T10:54:00.000Z

How I have been revising to pass the exam.

EIC will need to be written as Electrical Installation Certificate
PIR will need to be written as Periodic Inspection Report
MEIWC will need to be written as Minor Electrical Installation Works Certificate

Note that both these need attached to the first two but not the MEIWC.

A Schedule of inspection
A Schedule of test results

You will lose marks if you simply say Schedule of Tests.

To answer which is required, remember the clue is in the question.

A new circuit as been installed? Installed equates to installation, thus could be one of two, but since circuit added, is not a minor undertaking. This leaves us with Electrical Installation Certificate.

A report on the condition is required? There is only one report and this is the Periodic Inspection Report.

Initial Verification, or making sure in the first place, relates to the Electrical Installation Certificate.

Statutory documents are those passed by an Act of Parliment and could be The Health and Safety at Work Act 1974 or more likely the Electricity At Work Regulations 1989.

None statutory documents are likely to be BS 7671, Guidance Note 3, On site guide.

3/4 Rule of thumb Inspection and Testing. 2391 Exam

2007-07-17T10:12:00.000Z

So what is this rule of thumb?

When carrying out testing of an electrical installation the value of the phase and circuit protective conductors resistance is measured together to give (R1+R2).
Ze which could have been either measured, calculated or obtained by enquiry is then added to (R1+R2) to obtain Zs, but you knew that.
For a particular protective device BS 7671 gives tables as to the maximum value of Zs that can achieve disconnection within a specified time.
The problem is that when the value of (R1+R2) is measured the temperature of the conductors are likely to be at ambient temperature. Trouble is that the tables in BS 7671 are not relevant to Zs values measured at ambient temperature.
The resistance of copper is proportional to the temperature, so if the temperature drops the resistance drops.
Rather than having to measure the ambient temperature the 'rule of thumb' method is allowed.

To compensate for the lower temperature the maximum value of the Zs allowed needs to be lowered. 3/4 of the value of Zs is the worst case and thus acceptable to use.

A Zs in the table of say 4 ohms. would result in a corrected value of 4 times 3/4 which is now 3 ohms.

From a C&G 2391 viewpoint you will be given a Zs maximum value for a circuit and a set of Zs values that were calculated or else given (R1+R2) to which you need to add Ze to.

Show the formula you are using so that even if your maths are wrong you will still gets marks awarded.
Corrected Value For Zs = ZsMax X 3/4.

Provided that the calculated value is less than the corrected value then the results are acceptable.

C&G 2391 Inspection and Testing Exam Date Getting Closer

2007-07-15T20:36:00.000Z

The C&G 2391 Inspection and Testing Exam is this coming Thursday. I have been going through the past papers and timing myself and believe I must be missing something with my answers.
Part A which should take a hour to complete is taking me 20 to 25 minutes tops!!
Part B which should take a hour and half is only taking 30 to 45 minutes!!!

Some of the model answers to the past papers are almost the same answers to what I get. The keywords are there but perhaps in a different part of the sentence to those of the model answers. what could I be missing?

I can assume that the C&G are allowing the remaining time for thinking since I would not call myself a super fast writer, especially with a pen and paper.

I have been looking through the adverts for testing instruments to carry out inspection and testing of electrical installations. I wondered about whether is would be wise to get seperate instruments but soon dispelled this notion.

A multifunction instrument is initially cheaper to purchase.
The calibration cost is not that much dearer for a multifunction unit than the cost for a single funtion instrument.
If I lose a function or else a single instrument packs in, I cannot carry out the inspection either way so no advantage either way.
Some manufacturers claim that it is easier to use seperate instruments since there are not so many dials. I think that if someone is competent to carry out inspection and testing then a few dials are not going to be too taxing.
Having worked on some large industrial complexes the last thing I want is 6 seperate boxes to have to carry around, plus my tools.
One set of batteries to replace or carry spares for rather than 3 just in case 50% of the single testers decide to get flat batteries half way through a job.

My conclusion would be a multifunction unit for the reasons given above. Now do I need the extras?

Phase rotation is a must for me having an industrial background, since it can cause damage when large numbers of motors all go in reverse!!!!

I have never had to carry out an Earth Electrode Test but can forsee the day coming when I need to check on an 11kV/400 Volt transformer earth connection.

You ever worked on a construction site or one like i,t with water sludge dirt oil and grease all over the place? If so, then like me you can see the benefit of being able to record the results to download later. Ever dropped your notebook in dirty water and know all your results are lost?

I want an IP67 rated multifunction tester that can be dropped from 3 metres, if only one was made. So will have to settle for a shower resistant one.

C&G 2391 Inspection and Testing Day Questions for Roger 3

2007-07-10T09:01:00.000Z

A few more questions for Roger in respect of C&G 2391 Inspection and Testing

GS38 lists three steps when using an approved test lamp to check that a circuit is dead, list the three steps.
What is the recommended period between calibrations of test instruments.
Who determines the extent and limitations on a PIR?
Name one dead test that could cause injury through electric shock and one live test that could cause injury through electric shock to persons other than the inspector, explain the reasons why?
A system having a TN-S earthing arrangement contains a fixed electric heater that develops an earth fault, sketch the fault path for this arrangement.
What test is required for site applied insulation?
The following are recorded on the schedule of tests, what instruments would have been used to obtain the results? (40mS, 6.23kA, >100M ohms, 0.03 ohms)
Why does the main earthing conductor need to be removed when carrying out a Ze (Zdb) calculation?
What precaution could be employed when carrying out an insulation test between live and earth to prevent damage to sensitive components?
A circuit has a Zs of 500 ohms, show your calculation as to the the RCD to be choosen.
What is the main difference between a type B and type D MCB?
Why when carrying out a polarity check on the incoming supply of a new installation would this not reveal an earth neutral fault?
What disconnection time would be required for a 110 Volt system?
Under what circumstances would a PIR not be required for an industrial installation.
What is the requirement for obstacles used to prevent direct contact.
Give two examples where height is used to protect against direct contact.
What is the difference between conductive metal parts and extraneous metal parts?
Give two examples of enviromental influences that may require an inspector to shorten the period of inspection?
Give five reasons why a PIR may be required on domestic premises.
Where there is likely to be parallel paths present during a PIR, apart from tests what else must be done to check the cpc?
What does the abbreviations PEN, PME, MET mean with respect to BS 7671.
Give three systems that are not covered by BS 7671 but need to be considered during a periodic inspection?

C&G 2391 Inspection and Testing Day Questions for Roger 2

2007-07-10T00:26:00.000Z

A few more questions for Roger in respect of C&G 2391 Inspection and Testing

What does the letters IP stand for. What is the minimum IP rating for the top of an electrical enclosure? Finally what size particle does the IP rating relate to.
What document assigns an inspector the legal status of Duty Holder?
Where a single person is not responsible for a new electrical installation what title roles would need to sign the certificate?
What notice would not need to be present on a 230V DB but would be required on a 400Volt DB?
An insurance company requires a report on an electrical installation, which report would need to be produced and what additional pages would be required?
What is meant by the terms SELV and PELV.
What two methods can be employed for measuring the earth electrode on a TT system.
What is meant by the term TN-C-S?
Explain what is meant by direct contact and indirect contact. Name three methods of protection against direct contact.
When testing equipotential bonding what is the minimum resistance allowed? What is meant by equipotential?
Name three precautions to be taken when carrying out insulation tests.
What voltage setting needs to be selected when testing SELV and what voltage when testing a 230 Volt circuit.
Between what voltages must a low resistance ohm meter produce?
When using 2 30mA RCDs in series how can discrimination be achieved?
The mechanical operation of an RCD should be tested at what interval?
A domestic installation contains no CPCs on the lighting circuit, how old could you assume the electrical installation to be?
Explain what is meant by the 3/4 rule of thumb in relation to Zs.
Where an instrument is not capable of testing above 230volts, what calculation can be used to work out the phase to phase prospective fault current in a three phase circuit.
Explain what is meant by the 'touch voltage' and what is the maximum allowed?
Why is important to obtain the prospective fault current?
When carrying out a stage three test on ring final circuit the resistance rises around the ring and then begins to drop towards the end what is the likely cause.
Stage three of a ring final circuit obtains (R1+R2) but what else does it check.
On a ring final circuit the first and last socket gives 0.4 ohms but further round the ring the value drops to 0.2 ohms, what could be the cause?
In a standard twin and earth PVC cable, which conductor(s) will have the lowest resistance and which will have the highest?
Given an insulation resistance of 1.8 Meg ohms obtained from an overall test carried out on a 230 volt six way consumer unit. If 5 of the circuits have insulation resistances of 50, 50, 30, 50, 40 what is the insulation resistance of the sixth circuit and would this meet the minimum required for the installation?

More to come later?

C&G 2391 Inspection and Testing Day Questions for Roger

2007-07-09T17:22:00.000Z

Roger and I took the course together and I said I would ask him some questions that I will make up. So you might wish to check your knowledge ready for the exam.

There are three reports that an inspector can issue, what are these? Secondly give an example where each would be used.
What is the period between inspections for electrical installations in commercial premises? What reasons could an inspector reduce the period of time between inspections for a domestic premise?
What is the none statutory publication relating to test instruments? What size fuse and type is recommended to be fitted in an instrument's test leads.
Which earthing arrangement would have a maximum of 21 ohms if obtained by enquiry or the maximum allowed under BS 7671?
Give the order in which the first 5 dead tests would be carried out?
List the six tests that could be carried out on an 30mA RCD and what results would be expected for each test?
Explain what is meant by the terms Zdb, Ze, Zs, (R1+R2)? Show the formula for calculation of the earth fault impedance.
EEBADS is an abbreviation for what? What disconnection time is required for sockets when protected by a BS 88 fuse and also the time for other applications.
Give four examples of services in a building that would require bonding? What is the wording on the label required where an earth connection connects to services.
What is the difference between SELV and PELV? What voltage would an insulation resistance tester be set to test either SELV or PELV? What is the minimum resistance allowed?
When carrying out an insulation resistance test on a 6 Way consumer unit the following tests where recorded 5, 3, 20, 10, 20, 50 meg ohms. What is the overall resistance for the system and is this acceptable. Give three possible reasons for the lower tests.
What precautions would need to be taken prior to carrying out an insulation test.
The csa of the conductors in a cable are doubled, what effect would this have on the resistance. If copper is heated will the resistance increase or decrease?
A prospective phase/neutral fault current of 2.3kA is obtained along with a phase/earth prospective fault current of 3.4kA, which value would need to be recorded and why?
Ring final circuits can be tested using three stages. Briefly explain the stages? When testing at the sockets the resistance begins to increase after the third socket, what could be a possible reason?
Give three examples of where the polarity needs to be checked.

Not a full 20 but still enough to have a go at testing your knowledge.

C&G 2391-1 Exam and forms

2007-07-09T06:52:00.000Z

My exam is set for 18:30 on the 19 July 2007, so keep your fingers crossed for me.

Looking at passed papers and trying to predict what questions are likely to be asked may work but in my experience of externally set exams it is better to concentrate on testing your knowledge of the subject. Sat reading through your notes on it's own is not likely to help much.

For me it is best to choose a particular subject matter and write all you can remember on the subject then correct any errors and then add omissions from your notes. In this way you are amplifying your knowledge and re-enforcing your memory links such that you will have instant recall not only for the exam but later on in life.

You will have to believe me that I have none of the books or notes to hand as I write this. My subject matter is on the forms that are required by the BS7671 related to electrical testing and inspection.

A new installation requires the completion of an Electrical Installation Certificate that can be one of two formats. The first format contains spaces for two designers to sign, the installer and finally the actual inspector. The second is a shorter format and is where the designer, installer and inspector are the same person. Both forms require inclusion of two other documents, these being a schedule of inspection and a schedule of tests. It is also required that all documents are numbered generally in the format 1 of 5, thus giving the total number of pages, in this case 5 and also the actual page number, again in the case page 1. It is this certificate that gives initial verification that the new circuit or system complies with BS 7671.

At this point it is worth pointing out that BS 7671 is not a statuotory document but in almost all cases will compliance with BS7671 ensure compliance with the stauotory document, the Electricity At Work Act 1989. Under the EAWR the Inspector is called the Duty Holder and this title must not be taken likely since the maximum prison sentence could be 10 years. Testing instruments come under the EAWR and so their use or miss use could land the inspector in a court of law. To aid those involved in electrical testing the Health and Safety Exceutive has published a document called GS38 which again is not statutory but compliance with it will almost in all cases ensure compliance with the EAWR 1989.

The Schedule of Inspection is a list of items that need to be considered when inspecting an installation. All parts of the document should be filled in with a tick for compliance a cross for none compliance, N/A where the particular item of inspection is not relevant, LIM where that part is noted in the Limits and Exceptions.

The Schedule of tests contain results of tests carried out on the installation.

Test 1 Earthing conductor
Test 2 Equipotential Bonding
Test 3 Circuit Protective conductors (R1+R2)
Test 4 Ring Final Circuits
Test 5 Insulation Testing
Test 6 Earth Fault impedance (Would require verification of Ze)
Test 7 Prospective fault current

Time has won, more later, cya soon

C&G 2391 Inspection and Testing Day 1

2007-07-04T06:01:00.000Z

Day 1 of the course began with the normal fire exit procedures, and personal introductions. The tutor is a 50 y/o guy called Dave. Waiting for me was two books Inspection and Testing Guidance Note 3 known as GS3 for short and the ON-SITE GUIDE BS 7671: 2001 (2004).
The day was filled with brief snippets that would we were reassured several times come together over the remaining two days.
Will had more tonight as to content of Day one and Day two of the course.

I will say so far that there is nothing that seems to challenge either me or the other delegates.

C&G 2391, cable csa easy marks

2007-07-02T23:20:00.000Z

On seeing some of the past papers it appears that some easy marks can be gained by remembering basic electrical theory in relation to cables.

The conductors within a cable have a given resistance for a given cross sectional area (csa) depending upon the metal used. Copper is not the only metal since aluminium is also used.

The questions tend to ask if the length if increased or decreased and also if the csa is increased or decreased what value of resistance would be obtained.

Altering the length of the cable is equivalent to resistors in series whereas altering the csa is equivalent to resistors in parallel.

Let us assume I have a cable of a length and csa that gives me 1.2 ohm. (long cable). If I double it's length then I have 2*1.2 ohm or 2.4 ohms. If I half it's length then I have 1.2/2 or 0.6 ohms.

The same cable above is now doubled in csa so this will lower the resistance since we have effectively two resistors in parallel thus for same length the resistance will be 1.2/2 or 0.6 ohms.

So if we double it's length and also double the csa we get (2*1.2)/2 or 1.2 ohm. Notice that the resistance is the same, namely 1.2 ohm. If we half it's length and half it's csa then we have (1.2/2)*2 or once again 1.2 ohm.

If you imagine that the cable is an actual resistor it may be easier to remember when doing the exam.

Why is Zs important in electrical installations?

2007-07-02T16:43:00.000Z

If we take some fuse-wire and pass through it different currents we could create a time current characteristic graph. The graph would show that the relationship between current flow and time for the fuse-wire to burn out is not linear. As the current increase the time for the fuse-wire to burn out decreases much faster giving a curved line.

Since current flow is proportional to resistance for a given voltage then a fault having a zero resistance would create the greatest current hence the fastest trip time. There is however additional resistance to consider and this is the resistance or impedance of the supply (Ze) the phase conductor and circuit protective conductor CPC or (R1+R2), these combined make up Zs.

The higher Zs is, then the longer it takes for the fuse to blow since current flow will be a less. It is possible that the value of Zs is so high that even when a short is placed at the furthest point there is insufficient current flow to cause the fuse to blow.

BS 7671 lays down the times that over-current devices must operate and this means that for a particular device there needs to be a maximum value of Zs that will allow the device to operate within this time.

C&G 2391, 3/4 rule in relation (R1+R2)

2007-07-02T16:05:00.000Z

Most metals have a positive temperature coefficient of resistance. This means that the higher the temperature the higher the resistance. You did know that I hope?
Measure the resistance of a 100 Watt lamp when cold and then calculate the current flow when connected to a 230 Volt supply. Bet you did not get under half an amp?

So what does that have to do with the price of eggs or indeed calculation of R1+R2 with respect to Zs?

When using a low value ohmmeter the wiring, the supply will be dead. This means that there will be no heating of the conductors, since no current is flowing, so the resistance obtained is actual less than that which would be measured.

There is a calculation that can be carried out providing that temperature measurements can be taken but it is accepted practice to apply the 3/4 approximation.

Hang on though why is Zs all important when it comes to electrical testing anyway? More in the next posting.

C&G 2391, insulation resistance

2007-07-02T15:24:00.000Z

It would appear that some taking the 2391 exam are forgetting basic principles when it comes to insulation resistance.

Resistance in series, the formula is Rt = R1+R2+R3+R.... (Resistance value will be higher)

Resistance in parallel the formula is Rt = 1/(1/R1+1/R2+1/R3+1/R....) (Resistance value will be lower).

Where multiple circuits are to be tested from the same distribution board or consumer unit then the overall insulation resistance can be calculated using the parallel formula.

So for example, tests of 5, 20, 10, 20, 2 are obtained from individual circuits insulation tests on a consumer unit. What is the overall insulation resistance for the installation?

So we have Rt = 1/(1/5 + 1/20 + 1/10 + 1/20 +1/2) (Mohms)

thus Rt = 1/(0.2+0.o5+0.1+0.05+0.5) (Mohms)

Rt= 1/0.9 or 1.11111 (Mohms)

Notice that I have shown all the working out here. This is so that if I had made a simple error in the calculation I may still get marks for using the correct formula!!!!!

TT, TN‑C‑S, IT, TN-C Earthing Arrangements

2007-06-25T05:35:00.000Z

One area that always created a stumbling block was in remembering earthing arrangements since at the time the lettering did not create links. Using Tony Buzan's books however I have found that I can remember these by producing mind links.

In Latin earth is called Terra (Terre in French ) so we get Terra Firma, on solid ground.

So the first letter denotes if the supply is connected to Earth or Terra with the capital letter T. If insulated from earth then I is used, I for insulated.

The second letter denotes where the consumers earth is connected to. So T would indicate to earth. So TT means that the supply transformer star point is connected to earth and the consumers equipment is also connected to earth using earth spikes etc.

In an IT system the supply transfomer has no connection to earth but the consumers equipment is connected to earth using earthing spikes etc.

N stands for neutral and thus in a TN system the consumers earth is connected to earth via the neutral of the supply.
TN‑S is where the earth and neutral are fed back to the supplier with seperate conductors.
TN‑C is where the earth and neutral are fed back to the supplier using one conductor.
TN-C-S is where the earth and neutral are fed back to the supplier using one conductor but this time the connection of the earth to the neutral is not directly made at the consumers end thus there are two seperate conductors from the premises.

There is good article on this in pdf format form the IEE

BS 7671 and City & Guilds 2391

2007-06-25T05:07:00.000Z

Still have not took the course or the exam yet but still looking round for snippets of information that could appear on the paper.

A lighting circuit fed with a 6Amp MCB keeps tripping when attempting to do measure prospective fault current.

You would expect the MCB to sometimes trip since the current used to measure prospective fault current is much higher. From memory I seem to remember a figure of 25Amps. One source suggested that you could bridge the MCB out. If you did and at that very instant you turned on the main isolator a fault occured on the lighting circuit the whole lot could go up in flames since you could be feeding a 1mm csa cable with 100 Amps. Far better to measure R1+R2 and calculate. Still who am I to tell you I ain't passed yet!!!!!

2391-101 Inspection, Testing and Certification of Electrical Installations Zs Ze R1 R2

2007-06-22T10:57:00.000Z

From the City & Guild Chief examiners reports it appears that many get calcultations of Zs, Ze, R1 and R2 wrong. Remember folks I have not yet taken the course or the 2391 exam.

Zs is the sum of Ze, R1 and R2 seems simple enough. Zs= Ze + (R1+R2).

Ze is the external impedance. Although you can calculate the value, it is more normal that the value is obtained by measurment using a suitable instrument or by enquiry.

R1 is the resistance of the phase conducter

R2 is the resistance of the CPC or circuit protective conducter.

In practical test situations the value of R1 + R2 is obtained in one test so could in effect be considered as one value say Rt. So the equation would become Zs = Ze + Rt.

I just hope that in the 2391 exam you are not expected to know the values allowed in BS 7671.

So why Z and R?

Z is the impedance and applies to AC circuits.

R is resistance and applies to DC circuits.

2391-101 Inspection, Testing and Certification of Electrical Installations Testing of a 30mA RCD

2007-06-22T09:38:00.000Z

The chief examiner for the City & Guilds mentions that many taking the examination fail on this question. Again I have not passed or taken the course but would be tempted to write my answer something like this:

Using a RCD tester that is in calibration, set the instrument to 50% of the tripping current of 30mA, namely 15mA.
Carry out the test at this current for 2 seconds during which time the RCD should not trip for each half cycle.
Set the RCD tester to 30mA (the actual tripping current) and operate the test button. Record the time in mS that the RCD took to trip. This from memory should be less than 200ms if not used as protection against indirect contact, do this for each half cycle.
Where the RCD is used for protection against indirect contact set the level to 5 times the trip current, namely 150mA. On both half cycles the time to trip should be less than 40ms.
Press the test button on the RCD to verify that this functions correctly.

2391-101 Inspection, Testing and Certification of Electrical Installations

2007-06-22T00:36:00.000Z

2391-101 Inspection, Testing and Certification of Electrical Installations is according what I have read on the Internet and heard form those that have already taken the exam difficult to pass. The City and Guilds website only confirms the evidence. It would seem that less than half of those taking the exam pass.

Well it appears that I have to sit the examination, after first doing a three day course and also a one day practical. Before I commence the course I thought I would get familiar with what will be required to pass.

The chief examiner's report gives some indication as to where some easy marks can be gained.

One such area is in the sequence of testing. It makes logically sense that before power is applied to a circuit that it is tested since the testing could highlight any possible dangerous faults.
Isolate and Check was a slogan used in the mining industry. Before touching the wiring I would prove my voltage indicator, verify that the circuit or circuits are dead by testing at a few different points, once satisfied, verify that the voltage indicator still works. (Using a proving unit).
So which test comes first? Well what is the point of doing an insulation test if there in an open circuit on the phase, neutral or circuit protective conductor since any test would be meaningless. So in I am correct in my theory then the continuity of the conductors needs to be established.

For a simple circuit R1 + R2 is the phase conductor + the CPC impedance values and will be in ohms subtract from this any value for the leads that were obtained on the instrument check. The neutral should have the same csa of the phase conductor and should be almost equal to that of the phase impedance depending upon the circuit arrangement. For a three phase circuit the highest impedance is the one that could prevent a protective device operating thus this is the one used in practice against the chart to determine whether or not the reading is low enough and therfore recorded. Polarity can be checked at this point by making sure that single pole switches break the phase conductor and not the neutral or CPC.
Once continuity of all possible circuit combinations have been recorderd I would guess that each circuit is tested for insulation resistance using the 500V range of an insulation tester for domestic premises. Although the leads should be shorted together to verify the meter reads zero, I prefer to place one lead on an earth and then verify my contact by connecting the other lead to another earth location close by. Since all wiring would need to be tested it is important to have all the switches are turned on. Where there is two lighting circuits this means that all combinations of the switching needs to be verified. I doubt the exam would go beyond the simple two way circuit.
A reading of zero Megohms could indicate that a shorting wire is still in place or that there is a fault. If a low test is obtained between phase and neutral it could be that a neon is used on a fused spur or that a genuine fault is present.

If tests revealed a fault and I resolved the problem then I would begin the tests again in case during my investigations I had inadvertently disturbed the wiring.

more later, (eyes are tired)

BS 7671 and City & Guilds 2381

2007-06-21T11:06:00.000Z

Proof of knowledge of BS 7671 or the IEE 16th Edition wiring regulations are required for electricians in many UK industries. To prove you have an understanding of the regulations, you can obtain the City & Guilds Certificate 2381.
Provided that you have a good electrical background, the examination should not really pose too many problems. The examination is open book meaning that you are allowed to have for reference in the exam the IEE 16th Edition of the wiring regulations and also the IEE On-Site Guide.
Like my teacher friend says "It is more important to know where to find information rather than remembering the information". When I took my exam, I spent my revision time recounting where to find the information in the books. (I past by the way).
Do you need additional books to help you pass? If you taking the examination on it's own without taking a course then I would say they may help you understand some of the more difficult parts of the regulations or to offer information into the background of why there is a need for a specific regulation.

Electricity At Work Regulations EAWR

2007-06-21T02:32:00.000Z

Electricity At Work Regulations (EAWR)

These came into force in 1989, yet it would appear that many people are unaware of their duties under the act.
In a normal court of law a person is considered innocent unless the prosecution can prove guilt. With Health and Safety issues a person is guilty until they prove themselves innocent. At college one particular lecturer would constantly remind us that if someone died we could be doing a stretch of 10 years for manslaughter if proven guilty.
The EAWR is a statutory document, meaning that it is written law and thus contravening it means that you could be prosecuted. Like all law, the EAWR written in such a manner that Joe Blogs on the street could not tell what it means, but to lawyers it is clear and precise with no ambiguity.
There is a fundamental law that is always used and that is that ignorance of the law is no proof of defence. So if you did not know about the EAWR, tough luck mate, you could still be facing a manslaughter charge if you breached the EAWR.
So the EAWR is written for lawyers to understand and yet you can be prosecuted for contravening the regulations, does not seem very fair does it?

The Institute of Electrical Engineers IEE also publishes regulations which are not statutory, the latest being the 16th Edition IEE Wiring Regulations (The 17th Edition is due to be published soon). The 16th Edition IEE Wiring Regulations is now a British Standard (BS 7671).

BS7671 is written to go some way to actually offering practical advice in how to comply with the EAWR. If you follow the regulations set out in BS 7671 then you are less likely to find yourself in court for breaching the EAWR. Remember I earlier that in Health and Safety matters you are guilty until proven innocent. The police collect evidence in order that the prosecution can prove that a person is innocent, well since you need to prove your innocence so you need evidence also. BS7671 comes to your assistance by setting out different documentation that when completed can prove that you have exercised your duties.

I hope that the information above as shown how BS7671 compliance can prevent you from perhaps going to prison for 10 years. Look out for additional posting in the near future with respect to the EAWR and BS 7671.

Memory and Tony Buzan

2007-06-16T03:50:00.000Z

Earlier this week I attended a course on electrical testing and from this it was decided to go and take a City and Guilds Certificate in Inspection and Testing. Roger was a little worried about the prospect of remembering all the things that could be in the written exam. I told him there is a little secret to remembering and that these can be found in books by Tony Buzan.

Master Your Memory is on sale at Amazon for £6.39 is the first book I would get and then work through the book and try it out for yourself. I can still recount the story that places the planets in order from the Sun and not only that but also in relative size to each other.

Jim was going to take a degree and I mentioned about mind maps, when he got to university on the first day, one of his lecturers said "If you do not know about mind maps I suggest you begin by finding out". Jim had already got the books and had the basics. Tony Buzan also has a book called The Ultimate Book of Mind Maps which is £8.99 from Amazon. I have not read this one but have an older book. Traditionally, note taking for revision was done in a linear format. However Tony's work shows that the mind does not store data in a linear fashion but rather in the form of links, a bit like the WWW in that there is no organised structure. By using mind maps you bring out data from the brain and create a picture of the data. An A4 sheet of paper can have a surprising amount of data contained in a mind map.
I made a mind map of the computer revolution and was amazed at level of complexity of the map created and yet it proved easy to remember this map to use at a later date.
Let us go one further and imagine you are going to give a speech then you could write several sheets of words for the speech but you will generally have to rewrite it several times since many key points are either missing or not given in a logical sequence. With mind maps you place the salient points on it with respect to the subject to be spoken about. You can then either write out your speech or just take the mind map with you. Since you only have one sheet or two at the front of you any question from the floor requiring reiteration can easily be located and the answer returned.
Before knowing about Tony Buzan I was just getting passes in exams, then using techniques shown by Tony buzan I began to get far higher marks like credits and distinctions.

The only trouble is you have a brain that is full of stuff that does not go away. Like 0.4971 being the log of pi, the square root of 3 being 1.732 or that Ada Byron was the first computer programmer but also a druggie, Alan Turing was a homosexual that died in mystery, due to cyanide poisoning. Cyanide is contained in the pips of Apples. Apple is the name of the company began by Steve Wozniak and Steve Jobs. Snow White bit into an apple and slept until she got a kiss from a prince and the story made a hit when animated by Disney that later had Pixar to produce modern animations like Toy Story but is not Steve Job in there somewhere?

Car Insurance

2007-06-07T02:59:00.000Z

I got a quote from my previous insurer for over £300 and that was with a 15% discount. With getting a new Mazda 6 TS2 to replace the BMW116I SE, time to compare the market. Swift Cover came up best at £188 and then with extras the price was £236 approx. Since I do not work in; entertainment, gambling, modelling & professional sports. foreign or diplomatic service. scrap, second-hand dealers & merchants, market & street traders. bailiffs, debt collectors, bodyguards or doormen. motor trade, mobile mechanics, taxi or mini-cab drivers. couriers, despatch drivers, mobile caterers, or fast food delivery means I could go with them, oh and I am not under 19 or over 75.

Wonder who will be the cheapest car insurer next year?

Alto Kew 6411150 Patio Washer

2007-06-07T02:36:00.000Z

To match the Kärcher 2.640-212 T-Racer Patio Cleaning Pressure Washer Accessory you might be interested in the Alto Kew 6411150 Patio Washer . It is available from Amazon UK for £49.93 at the time of writing.

Manufacturer's Description:
"The Patio Cleaner is 6 times quicker than the use of a standard lance, avoids stripes and stops splashing onto other surfaces.
The Patio Cleaner has a counter-balanced nozzle that spins in operation widening the cleaning area of a standard nozzle by 6 times. It hovers in use making it very easy to use and keeps the spray pattern nice and flat which means a very even clean and when the patio dries there are no stripes. The cleaning hood also stops spray going onto walls and patio windows which means you don't have to clean all these areas down when you've finished the patio.
You can also pull the nozzle into the head and clean decking and fence panels without damaging the wood.
Fits all Nilfisk-ALTO and KEW models except the C100.1-5. "

Vine weevil (Otiorhynchus sulcatus)

2007-05-22T00:39:00.000Z

I had these weevils in my garden a few years back and they destroyed most of my Fuchsias one year. The little white grubs with the brown heads ate all the roots and then the plants died. In springtime the grubs changed into adults. They are about 9mm long, dull black, beetle like with 6 legs. They do not move fast and tend to keep hidden during the day. The adults would feast on the Fuchsia leaves leaving irregular notches.

Armillatox was available to kill the eggs, but due to high costs in getting approval in the EEC for use as a pesticide (around £3 000 000). Well you would mix in a ratio of 500 to 1 solution with water and spray over the compost every fortnight during period March to October and then from November to March every month. You can get Armillatox to use in the garden for other purposes in the UK for about £8.45.

To kill the Vine Weevil in my garden I discovered Bio Provado Vine Weevil Killer which you mix with water and water into your containers. It is systemic, meaning that the plant absorbs it and the pests die once they begin to eat the plant or roots. Since PBI is now part of the Bayer group the product is renamed Bayer Provado Vine Weevil Killer. The active ingredient is Thiacloprid which also helps control Whitefly, Blackfly and Greenfly. Three applications a year are all that is needed. Cost is around a tenner for 750ml.

Levington compost can be obtained that contains the pesticide imidacloprid and other 12 months protection.

There are also natural enemies of the vine weevil like the centipede, which should not be confused with the millipede which is a pest. Yet another is something called nematodes. These are tiny creatures that enter the larvae through bodily openings and kill the larvae. You can buy the nematodes commercially like; JUST GREEN VINE WEEVIL KILLER SMALL PROGRAMME or Nemasys® VW biological vine weevil control . Steinernema kraussei is used for temperatures above 5C/68F while Heterorhabditis megidis works better above 12C/54F.

Like most insect pests, encouraging birds, frogs, toads, shrews, hedgehogs and predatory ground beetles will reduce vine weevil attacks.

Agralan Insect Barrier Glue around pots and greenhouse staging can trap the adults.

Hope this helps eradicate your vine weevil damage.

Can you help find Madeleine McCann

2007-05-16T18:50:00.000Z

CAN YOU HELP???

Madeleine McCann was abducted from her parents rented holiday apartment in Praia da Luz on the evening of May 3rd 2007.Her family need your help to find her – any information at all, no matter how insignificant you feel it to be, could be crucial to bringing Madeleine home.

From outside of the UK please contact Crimestoppers on 00 44 18 83 73 1336
If you’re phoning from within the UK contact 0800 555 111
Visit The Madeleine Fund Website

Notice the distictive flash in her right eye!!!

Water Butts

2007-05-09T20:14:00.000Z

The weather this year is supposed to be a scorcher which is great if your a sun worshiper. However what about the gardens this year? If the water becomes short then hosepipe bans are likely.
Last year most companies sold out of Water Butts, are you going to be one of the unlucky people that does not get one this year??

I have added some that are available at the moment on the gardening database website from different suppliers.

Hydrogen the greener gas

2007-05-08T20:53:00.000Z

I read an article at msn called Top 10 green motoring myths. It says,

In the meantime the biggest headache for scientists is how to extract and store hydrogen so it can be made available as a fuel, without the need to first use large amounts of fossil-fuelled electricity.

To me the answer is wind power.

Using wind turbines, electricity could be produced that would be used in obtaining hydrogen from water by means of electrolysis. (The oxygen produced could also be stored too). Since the wind is free the costs are manpower, capital investment in the plant and water to replenish that used in the process.

Why won't it work, what have I missed???

Shh A price drop coming Friday 4th May 2007 12-3pm

2007-05-03T21:33:00.000Z

Visit here on Friday 4th May 2007 12-3pm for Prices Dropping at Comet (UK)

Price Crashing on:-
Panasonic 32" HD Ready Digital LCD TV
JVC 20" Digital LCD TV
Philips 26" HD Ready Digital LCD TV
Proline 15" LCD TV
Proline iPod Speaker Dock
Sagem Freeview Box
Proline Air conditioner
HUSKY HUS-HM71 - Chiller
BOSCH KGV28V00GB - Fridge Freezer
PROLINE TFP135B - Fridge Freezer
PRESTIGE PR60HOBG gas hob
PRESTIGE PR60FSDOE electric cooker
Zanussi ZWF1221 1200 spin washer
Indesit WIL163S - 1600 spin washing machine
SONY NAV U-50 GPS Navigation
SONY NAV U-50T GPS Navigation
SAMSUNG YP-K3JQB 2GB MP3 Player
NETGEAR WIRELESS NETWORKING KIT
IOMEGA 500GB EXTERNAL HARD DRIVE
NORTON INTERNET SECURITY 2007

1 to 18 Golf

2007-04-24T01:01:00.000Z

Since I have taken up the game played by men with little balls, (women too). Thought it would be a good idea to create a website about golf. I had originally intended to use the URL of 1to18.co.uk for a different purpose to golf. However since golf involves playing 18 holes I thought it would be more suitable to golf.
At the moment I am in the process of getting the adverts working.

Asp.net Adrotator is used and this in turn is connected to a SQL database containing the advert details.

I will keep you informed of the progress of the website as and when new content is added.

Visit 1to18 golf and see the ads working

Will be taking in other banners for a fee later. Check on topic banners as to when

The Nokia N95

2007-04-23T18:18:00.000Z

My brother in law was on about a new mobile phone the other day (Cell Phone) and I said to him that the Nokia N95 was no good for him due to all the extra features it has on it. To my surprise he was then determined to obtain one.
So what is different about the Nokia N95, well if you are into photography you will appreciate the Carl Zeiss lens used. You will also like the 5 megapixel camera. (Pixel is derived from Picture Element and basically the larger the number the better is the quality.
For fuller specs visit shopping.me
If he gets one I will pass on what he thinks to it

Karcher Pressure Washer

2007-04-23T18:04:00.000Z

Ordered the Kärcher 2.640-212 T-Racer Patio Cleaning Pressure Washer Accessory from Amazon in combination with the Karcher K4.99M Upright Domestic Pressure Washer which can be viewed at Amazon.co.uk. One I have taken delivery of the items I will let you all know my impressions of the product.

You can find for details of these at shoppingonline.me

Lawnmowers

2007-04-20T21:34:00.000Z

Just been adding lawnmowers to a SQL database, the idea eventually is to allow users to choose a mower based upon their requirements. You can see the list of lawn mowers at two locations, so far. shoppingonline.me.uk and also at lawnmowerdatabase. Still working on how to get the data out of multiple tables so I can present all the data on one page. Well rather to input the data in an easy form rather than filling out the tables used individually.Well more on this in a later

Road Congestion Charges

2007-03-11T00:46:00.000Z

So there is talk of having a toll on UK roads to ease congestion.
What a load of bull.

Initially there will be a reduction until wages are ajusted to cover the toll charges.

Food prices and other goods will rise and make the poorer members of the UK population worse off, since transport costs will rise.

Constructive criticism is offering advice that is considered to be beneficial when being critical. No good saying that is crap without offering an alternative.

The conjestion (search engine spelling mistake)is caused by the volume of traffic using a particular stretch of road. However if you look at a section of a motorway then this cannot be true since the volume of traffic can and does excede that of other types of roads unless influenced by external factors like roadworks accidents or cars wanting to exit the motorway.

Cars exiting the motorway, why are they responsible for holding up traffic flow on the motorway?

Where there is a large volume of traffic wishing to leave the motorway the design of UK roads is such that there is insufficient throughout using conventional roundabouts. Traffic wishing to leave the motorway are forced to wait at the end of the motorway until traffic that may or not being going in their direction clears.

If the traffic that wished to turn left had a bypass and joined to the main carriageway later then these would only be delayed by having to merge with traffic on the road.

If traffic on the carriageway of the road crossing the motorway could fly over or under the roundabout then the only traffic that would now cause a delay to the traffic coming off the motorway would be those wishing to make a right turn.

In conclusion to the first part, roundabouts need to make such that traffic using them is traffic wishing to make a right turn.

Where is the money coming from?

If we assume for one moment that all persons using a road are paid £6.00 an hour then every lost minute is a loss to the country of 10p. Not a lot until you calculate how many cars and lorries can be delayed in a traffic jam of 10 miles.

Green gasses are another issue that would also be reduced. If you have a mpg indicator in your car, travel at 70 on the motorway and note on the level the reading. Mine did 38 to 48 mpg. Now check your average over a couple of months, mine read 32mpg. The difference is due to the constant stop start or slowing and accelerating that the design of UK roads creates. If the roads allowed for a constant speed over longer distances the green house gasses would be reduced.

Roundabouts are one of the obstacles to a constant speed, irrespective of the time of day and thus the volume of traffic.

Dating -- Why are there so many single people

2007-03-08T14:34:00.000Z

In my life it seems that there are many people, both male and female that are not paired up. Yes, some are single but many would love to be in a relationship.
Some of those that stated they had no interest in having a relationship do in fact want to have one. This is because when cupid calls they open the door to love.

Why is it that there is so much difficulties in finding love.

Do we expect that we will find the perfect partner for us?

Are we looking for the impossible?

Pull The Boys aimed at women to help find a man to have a relationship with

Pull The Girls is aimed at men to try and get notches on their belts. However what many of us men do not know is there is a yearning deep withing to find love and if sex is a motivator then let it be the reason they go out on the prowl.

Well let us face it, how men would be willing to say they are going out to look for a wife.
Ask if he is going out to get into bed with a women and I bet he will say either yes, or maybe?

CF Bulbs and statistics (or Lies?)

2007-03-07T09:36:00.000Z

Compact fluorescents are supposed to save the planet and save us loads of money.

A typical 20W CF lamp consumes only 20% of the power for the same light output as a 100W incandescent bulb. In theory this would mean that your running cost is a fifth of the cost.

Now take the time your light is turned on in a room in your house. If the heating is turned on then the 20W of heat generated by the lamp is added to the heat output of the primary heating source. Since the room is generally controlled by a thermostat then this 20W lamp will reduce the amount of time the primary heat source operates. Now if we have a 100W lamp in the same circumstances then the primary heating source operates even less.

My theory is that there is no difference to your energy costs when you have the heating turned on and are using CF or incandescent lights.

Money Saving with Vinegar

2007-03-07T09:31:00.000Z

I have been busy putting some money saving ideas involving the use of vinegar on my gardening database forum. There are a lot of uses for common household items and I hope to be adding to these soon. Also if others do too all the better.
I like the one for keeping the windscreen smear free in the rain simply by wiping the blade with vinegar.

Joss Stone is off men

2007-03-06T19:23:00.000Z

PR Inside says Joss Stone is off men since her break up with BEAU DOZIER. I think she should not be too hasty about men just learn from the experience. Men are not women and think and act different that is what she should be learning. She needs to accept men for what they are.
She should tell others of her woes at the Dating forum For Women

Boiler TDS and RO Calculator

2007-03-06T16:29:00.001Z

So you have a steam boiler with automatic control of TDS to maintain the level. Just what savings could be made a reverse osmosis unit.

Well to help I have created an online calculator that will work out the blow-down rate provided that the average steam flow, feed-water TDS, and the maximum allowable TDS of the boiler are all known. It will also work out how much this loss will amount to in a year given 50 weeks 5 days production of 24 hour operation.

It will further go to show loss achieved using RO and thus the potential savings.

Not sure if an EDI unit applied to the permeate of the reverse osmosis is feasible but also added a calculation just in case.

I calculated a saving where borehole is used for a 15 Tonne steam feed of £402768 based upon a tonne of steam costing £24 to generate.

Anyone wishing to work leaner and those involved in TPM that use a steam boiler should look at Reverse Osmosis Savings

Boiler TDS and RO Calculator

2007-03-06T16:29:00.000Z

So you have a steam boiler with automatic control of TDS to maintain the level. Just what savings could be made a reverse osmosis unit.

Well to help I have created an online calculator that will work out the blowdown rate provided that the average steam flow, feedwater TDS, and the maximum allowable TDS of the boiler are all known. It will also work out how much this loss will amount to in a year given 50 weeks 5 days production of 24 hour operation.

It will further go to show loss acheived using RO and thus the potential savings.

Not sure if an EDI unit applied to the premeate of the reverse osmosis is feasible but also added a calculation just in case.

I calculated a saving where borehole is used for a 15 Tonne steam feed of £402768 based upon a tonne of steam costing £24 to generate.

Anyone wishing to work leaner and those involved in TPM that use a steam boiler should look at Reverse Osmosis Savings

Water companies, water shortage, RO, Wind Power

2007-03-06T16:13:00.000Z

I always seem to come up with some weird concepts so here is one, note the date for reference in case it gets used.

I was chatting to a Reverse Osmosis engineer and it came to me that the droughts of last year could be avoided by the water companies around the Kent area of the UK.
If large reverse Osmosis plants were to be installed along with wind generators then during the times of strong winds the RO plant could be used to extract potable/drinking water from the Thames or other rivers in the area.
Apart from the initial installation charges the running costs would be cheap since the power is generated with the wind.
There is also another benefit to the electricity supply companies in that they will not need to increase or decrease the supply based upon the wind. This is one of the concerns of the increasing usage and dependence of wind power in that it is not available 24/7.

There are also several other ideas forming that have been sparked by balancing wind power and conventional electricity supply.

New Dating Forum

2007-02-20T03:39:00.000Z

I have began a new forum on my Pull The Boys website that is called Dating Forum For Females. It is based upon YAF like the other new forums I have created lately.

CE with respect to TPM

2007-02-19T23:55:00.000Z

Within TPM there is something about changing guards from metal to acrylic/perspex so that autonomous maintenance can be undertaken easier by being to look through the at the machinery to be checked. In the Certificate of Conformity in the EEC there is a little piece that says the equipment should not be modified without having to issue a new certificate. I was wondering how to overcome this obstacle?

Reverse Osmosis Operation

2007-02-18T23:11:00.000Z

I am going to be creating some pages soon on my Arachnid Spider website in a folder called reverse_osmosis. The pages are to show how it is possible for a company selling Reverse Osmosis Systems to make additional revenue from the website.
In the pages I intend to show how the company can raise the numbers of hits to the website though the use of AdWords, how the components that they use could also be used to sell to visitors to the website.
Google AdSense will also be shown as a tool to generating additional revenue without the company losing any potential customers.
The suppliers of the components may also be interested in paying to have banner ads placed on the website.

In order to demonstrate the web pages showing Google AdSense banners etc it I have to make the website look authentic apart from the actual selling of the system. Well with this in mind I had to go and find out exactly how reverse osmosis works in order to add content to the web pages.

To understand Reverse Osmosis you need to first understand how osmosis works. Oh Osmosis is the way that plants absorb water through the roots, transpiration is how the plants get the water to flow through the rest of the plant.

Take a 'u' tube and put water in, you will notice that the water levels in either side. Now add salt solution to one side and again the levels are the same.
This time in the base of the u tube we are going to fit a semipermeable membrane. One side we fill to a mark with water, to the other side we fill to the same level with a strong salt solution.

A strange thing happens, the level in the salty side rises and the water side lowers.

This carries on until a certain difference is achieved, this is known as the osmotic pressure.

Hope that little lot made sense, it will on the actual web pages since there will be diagram to give a better representation.

Not going to bore you will the finer details of the mechanics of the process but will have to on the web pages.

So we now apply a pressure greater than the osmotic pressure and this time the water travels through the semipermeable membrane but the leaves the salt behind. Well in a nutshell that is it how reverse osmosis works.

In practice the water is softened to remove potential lime scale then passes through filters to remove solid particles. High pressure pumps generate up to about 40bar in some cases to overcome the osmotic pressure.
The water passes through the centre of a tube that is surrounded by a semipermeable membrane. Pure water passes to the outer surface where it is collected and if required passed on to a second stage of filtration.

TDS levels and Reverse Osmosis

2007-02-18T23:00:00.000Z

I am a little perplexed at the moment. A boiler is rated to run with a TDS of 3000. A Reverse Osmosis sytem is installed to reduce the amount of TDS in the feed water. The chemist from the company supplying the chemicals says the boiler now needs a maximum TDS of 1000.
Is the reason that the chemist is maintaining the lower TDS so that the ammount of chemicals required is more than would be required if the TDS was allowed to operate up 3000?

Is there another reason that the Chemist is right in saying that the maximum TDS should be 1000?

I welcome your comments on this issue

TPM Reverse Osmosis and boilers

2007-02-17T21:15:00.000Z

A main part of TPM is something called Kaizen, the latter translated in English translates to continuous improvement. Well this blog is basically how money can be saved where industrial boilers are used.
TDS is a term used within the boiler industry, and is an abbreviation standing for Total Dissolved Solids. The thing is that you put water into a boiler and take off steam, the water that is left starts to become concentrated because you keep adding more water to make steam. Okay so far? You know when you boil a pan of water you get bubbles coming to the top? Big boilers do the same thing except that is the concentration of TDS gets to a point the bubbles no longer burst and eventually the bubbles get pushed up and into the steam lines. The last thing you want is wet steam and also the chemicals in the water can cause real damage to other parts of the system. Not very nice.
There are closed loop controls that discharge some of the boiler water when the TDS concentration becomes too high, other boiler installations require manual discharge of this excess TDS.
You can imagine that the water from the boiler is under pressure and at a temperature well above 100 degrees centigrade. What a loss of energy!!!!
So how can we reduce this loss, mmmmm, well if we could reduce the level of TDS in the water that we add to the boiler then Hey Presto, a reduction in the time before having to lower the TDS concentration in the boiler.
How can we reduce the level of TDS in the feed water, first in having an efficient condensate recovery system. This also means that the feed water is at an hotter temperature saving money heating it up. Condensate is steam that has condensed back to water, and this is almost pure with no TDS. A perfect condensate recovery system is still waiting to be created so we still need to add more raw water.
Now we come to Reverse Osmosis. I will tell you more details in another blog how they work but for the moment you will have to believe me that they remove most of the TDS from the raw water and thus can save money if installed.

Total Productive Maintenance Forum

2007-02-17T20:37:00.000Z

I do not know if you have heard of something called TPM, or Total Productive Maintenance? If you have and are interested in a forum intended to cover all aspects of this and associated concept then you might be interested in the first forum I have up and running. You can visit at TPM Forum
Heading so far are:-
5S Seiri Seiton Seiso Seiketsu Shitsuke
JIT Just In Time
Kaizen
Kanban
KPI
Mind Map
Pareto Analysis
Reliability Centered Maintenance
8 pillars of activity - Kobetsu-Kaizen - Jishu-Hozen - Hinshitsu-Hozen
Poka-yoke
SMED (Single Minute Exchange of Die)
5 Why Analysis

YAF or Yet Another Forum

2007-02-09T01:41:00.000Z

I downloaded asp.net2.0 version of a forum from Yet Another Forum and have spent the last couple of days integrating into my Gardening Database website. You can see the results at GDB Forum.

The problems I had was cheifly with the web.config setup. YAF download comes with a file called default.config and on a new website you simply need to rename it web.config. I had however already got a web.config with needed tags. I tried to incorporate the YAF into the old web config but had no joy. My solution was to rename my original web.config file to webback.config, rename the YAF default.config to web.config and then start adding items from the now named webback.config. At each stage I tried and verified each bit to ensure that the YAF and transferred bits did not create errors, where they did I only needed to make slight mods.
No doubt many of you will have downloaded Microsoft's SQL 2005 like me, well another problem I had was in getting the configuration setup to point to the database file. My solution short of a better one was first to put in the location in file notation C:/ etc etc and this worked once I had created a blank database.
Since I was to upload the new pages, database etc I needed to change this from static to something a little more dynamic. I used
.\SQLEXPRESS;AttachDbFilename="DataDirectoryForum.mdf" and it worked.

I use a master page and a website theme. In the web.config file I included within the <page> tags styleSheetTheme="yourstyle" so that all pages that have the masterpage directive in would use the same theme. YAF does not use the masterpage and this caused one or two little minor problems. The <head> used in the YAF pages needed converting to
<head id="Head1" runat="server">

There were a few other errors to do with XHTML validation, but nothing too serious.

Adsense, loss of revenue??

2007-02-05T23:24:00.000Z

Hi again
I have read a few blogs and forum posting about the reduction in revenue from adsense recently. It would appear that many companies that allow workers to use the internet are removing google adsense from pages.
What this means is that the visitor is getting the information but is not eing tempted to click on the google ads.
When more and more companies do the same, I wonder whether it may mean an end to google adsense as we know it?
Does anyone know if it is possible to change the keyboard on a Toshiba Satellite A30. My keys are coming off??
Well If I get a few more people clicking on the adsense ads I might be able to buy a new laptop.

Gardening Database new features

2007-02-03T20:33:00.002Z

I have been adding some extra content to my gardening database website.
There are a lot of gardens that are worth visiting, either for the shear enjoyment or to gain inspiration, location list gives a list of those I have entered so far. The format is not to my liking but will suffice until I come up with a better page layout.
The wife turned the computer off without shutting windows down. This resulted in me losing the publishstate.xml file. Microsoft was unable to duplicate the fault according to their website but I hope they see this blog. To resolve the publishstate problem I had to use search to locate it. Mine was at C:\Documents and Settings\Mandy\Local Settings\Application Data\Microsoft\WebsiteCache\ Letters in green need to replaced with your directory names. Once there, create a folder that matches the name you have given to your website. In my case this was GDB (not an inspiring name is it).
Use the copy website again and then close down and check that the folder now contains publishstate.xml.
I used part of the Club Web Site Starter Kit but ended up with a problem.