Tracking down electrical faults

I've recently rewired my house. All new wiring and consumer unit. All seems to have gone well, apart from the ground floor lighting. I installed a light fitting in the kitchen and it flickered occasionally. I didn't think much of it, until this morning when the MCB went on that circuit. Also the outside light which is on that circuit blew the bulb a few weeks ago. I'm going to look over the circuit tonight, and check all the connections to the junction boxes.

I was wondering if anyone had any tips/hints about tracking down electrical faults. Does the lightbulbs blowing suggest a particular problem? Could the light fitting itself be at fault?

Thanks in advance.

Dan

Reply to
Dan Collier
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I'd have said that the flickering and the MCB tripping are the significant things, not the bulb blowing which is a normal event.

Sounds like a nail through a cable, or some other short.A faulty fitting sounds unlikely unless you have gone real cheap-o.

A few stabs in the dark (!) might save a lot of work:

Any clues as to when it failed or flickered which might indicate where the problem is? eg family members dancing upstairs suggesting problems under joists.

Check the wiring to pendant fittings for whiskers of stranded wire.

Which fitting gave you most trouble when fixing it? The one you swore at most 'cos it was inaccessible?

Check any fittings with metal casings - they will be prime candidates! Plastic light switches in plastic boxes won't do that.

You have put the cables through joists by drilling holes through a few inches down (correct) rather than 'notching' them then nailing the boards down (wrong)? Too easy to pierce the cable.

Any trunking used? Fixing screws or nails through the cable?

A fixing screw for a fitting somewhere penetrating a cable and shorting it?

A live wire with too much insulation removed? Inside metal boxes or fittings or the consumer unit?

Good luck!

Phil

Dan Collier wrote:

Reply to
P.R.Brady

By "flicker" do you mean slight changes in brightness, or goes completely off briefly?

Not sure if the bulb going tells you much, but it might be worth monitoring the supply voltage for a while.

It sounds like you need to repeat the basic circuit tests as a starter. So for example taking all bulbs out, disconnecting the circuit at the CU and measuring DC resistance between all conductors (should be infinite!). Then find the last point in the circuit and disconnect the cable. Twist all the conductors together and repeat the resistance measurements back at the CU. If you combine the results with table 9A in the on site guide (brown book page 158) that should give you a good indication if there is something odd going on. Things like L to E should give the same result as N to E. L to N should be slightly lower resistance. Finally disconnect anything electronic from the circuit (dimmers, transformers etc), and do an insulation resistance test.

Reply to
John Rumm

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