Discuss C&G 2391 tricky question in the Electrical Forum area at ElectriciansForums.net



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Hello guys. I've come across this question when studying for my exam. It was one of the long questions with scenario. The scenario (shortened as I don't want to bore you): you were asked to extend a lighting circuit in the office and add two 55W fluorescent luminaires. One of the questions: 12 months after the completion of the extension, one of the luminaires requires replacing. Before undertaking the replacement of the luminaire list three items that need to be concidered. I found it very confusing, it may be related to the safety, obtaining the permission and isolation of the circuit or maybe rather to what caused the failure, e.g. overheating, external influences. Any ideas?
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Given it's for an I & T course, previous test results/certification would be a good place to start, comparing them to the current readings?



As above. Also can you get access to change the luminare without casuing danger to yourself and the staff in the office as there may be desks, office equipment etc under the fitting. Can you isolate the circuit without casing problems with the other light being off. When testing the circuit can you do so safely with staff in the office. Just some thoughts, good luck.


Access - Height do you require access equipment
Isolation ,without disrupting the supply to other lights which could couse a risk
Carry out a risk assesment
reason why it needs replacing , damage due to vandalisum or in a position where it is at risk of damage
do you require the area to be vacated if the area where the light is fitted is populated all risk assesment based i think


yeah polo1 is on the money previous test results should give you the biggest insight into whats what. Sometimes just just trhink naturally as a spark put yourself into that scenario as if you were at work and think logically as to what you would do if it were a real situation. Although they do word the old questions in bit odd if you think methodically like at work you will tend to be correct. Good Luck mate.


Many thanks. Didn't expect so many replies in such a little time. I'm new to this forum. Exam's on Thursday, worked really hard but some questions are really tricky, fingers crossed.


I'm looking at this differently, try looking at Reg 132.16.
That's my take on your question. :)

Adam W

What would the previous test results tell you if the lights were only installed 12 months ago, by you, and presumably they were acceptable because you wouldn't have just recorded unacceptable results?
I think they want you to consider why the fitting needs replacing, precautions which need to be taken such as whether you will need to do the work out of hours or just use suitable barriers and signage.


Thanks Adam. This is why I asked this question. Since you're replacing the light fitting you've installed and tested yourself no longer then a year ago I was in doubts. Furthermore, the question says to state 3 items that need to be considered before undertaking the replacement so there's nothig to compare the previous results to. I would go for risk assessment, permission to isolate sypply to lighting circuit and inspection of old luminaire ("why the fitting needs replacing").


I think JDD has a point. It does not say with what the fitting is being replaced with,like for like or something completely different which may have different current requirements. A typical vague question from C&G. Depending on the number of points the answer is worth will depend on the amount of thinking/complexity you should give to the answer. If it is only worth a couple of points then the answer is likely to be on the simpler side, if lots of points then you need to consider the more complex possibilities. You do not want to waste time on the simple questions so divide the total time by the total number of points and allocate the result as minutes per point. Do use the terminology in GN3 as from what everyone says they like it and it is a MUST when naming test instruments. I think your answers are good but the question does say before the undertaking so I would not include the inspection of the old fitting as you could only do this when you had started the work so I would add safety of people in the office. You could always say "Assuming like for like replacement" at the start if that is one of your assumptions.

Richard Burns

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I would also be looking at the reasons for the replacement as it should still work OK after one year. Potential change of use making the previous fitting unsuitable for the location? Not the only thing, as the other answers are also good.

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