BS 7671 and City & Guilds 2391

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!!!!!