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wiring for "bulbholder"

Postby Marlburian » Sat Jan 12, 2013 6:44 pm

A ceiling light bulb flickered out of use but was OK in another light, so I turned off the mains and unscrewed the fitting. The part that screws into the ceiling had 34 years of dust and gunge in it and as I was cleaning that out the "bulbholder", or what the manual calls the lampholder, came off in my hand - honest, the terminal screws were that loose.

So I have:

a green earth wire still connected to the ceiling fixture;
two red live wires twisted together at the ends;
two separate neutral black wires;
and a lampholder with three terminals, two of which obviously relate to the contact studs for the bulb.

If there was just one neutral wire I'd stick it and the two live wires in the obvious terminals - but what about the other neutral wire?

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Simply Build It

Postby stoneyboy » Sat Jan 19, 2013 11:13 am

The most likely arrangement will be that your two black wires are switched live and neutral.
Try connecting these two into two contact stud terminals and your twisted pair of reds into the spare terminal.
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Postby kbrownie » Mon Jan 21, 2013 1:31 pm

The two reds twisted together are permanently live they belong in the live loop (this is not the live of the lamp holder, BTW that is the correct term to use).
The cpc/earth cables connected the earth terminal of fitting.
You will now be left with two blacks, one is neutral one is switch live (becomes live when switch is closed)
and should be sleeved or marked red to identify this.
I recommend that you test using an approved two pole voltage tester to identify which one of these black conductors is live, when switch is closed.
Then the live goes to live side of lamp and neutral to neutral side of lamp.
It is import that this is done correctly, it maybe that in this case the light works which ever black is terminated at live/neutral of lamp, but this can be unsafe and leave exposed metal contact of the lamp holder live and also if any alteration/extension of circuit are made in future, that a neutral conductor may get looped in to the switch live.
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