Junction Box Question

Thought I had best check up on this before I do it ...

I need to connect three low voltage spot lights with three transformers to the main lighting circuit.

Can I do use a junction box to link the mains feed to each individual spot? This means that there will be four sets of twin and earch going into the junction box (I need to extend the T&E to the transformer position for each fitting).

How should I wire all four T&E's into the junction box? Had a quick look at one today - the sort where you get four terminals around the outside and two in the middle. Its going to be a pain to connect all four into the two terminal blocks in the middle - am I looking at the wrong type of junction box? Is it acceptable to bridge the terminals to allow me to connect 2 lives and 2 neutrals at the top of the box and 2 at the bottom bridged together?

Also, how should I terminate the earth from the mains feed. This isnt needed for the transformers. I presume I should terminate it inside the junction box on a spare terminal. Is it acceptable to just cut it short and not use it?

I havent started this work yet before I get told off for not knowing what I am doing!!

Thanks in advance,

CM.

Reply to
Charles Middleton
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"Charles Middleton" wrote | I need to connect three low voltage spot lights with three transformers | to the main lighting circuit. | Can I do use a junction box to link the mains feed to each individual | spot? This means that there will be four sets of twin and earch going | into the junction box (I need to extend the T&E to the transformer | position for each fitting).

Yes, but remember that junction boxes are supposed to be accessible. You might be better going from fitting to fitting to fitting.

| How should I wire all four T&E's into the junction box? Had a quick | look at one today - the sort where you get four terminals around the | outside and two in the middle. Its going to be a pain to connect all | four into the two terminal blocks in the middle - am I looking at the | wrong type of junction box? Is it acceptable to bridge the terminals to | allow me to connect 2 lives and 2 neutrals at the top of the box and 2 | at the bottom bridged together?

It would be acceptable, but probably neater to get a bigger (20A or 30A)

3-terminal box. Remember that the outer sheathing must continue to inside the box ie no coloured insulation visible outside the box.

| Also, how should I terminate the earth from the mains feed. This isnt | needed for the transformers. I presume I should terminate it inside the | junction box on a spare terminal. Is it acceptable to just cut it short | and not use it?

No. You must connect the earths in all the T&Es and run the earths (circuit protective conductor) right up to the transformers whether or not they are double-insulated. All mains circuit wiring requires a cpc. There should be a parking terminal on the transformers for the unused earth. All earths require green-yellow sleeving.

If the T&E you buy is new colours (brown/blue) and your house is wired in old colours (red/black) then you also need to buy a little label saying "this installation uses old and new colour schemes" and stick it on the consumer unit.

Owain

Reply to
Owain

Always a good idea ;-)

Yes, a junction box is the obvious and preferred way.

I wouldn't use a 6-terminal box - too cramped, given you need only 3 or

4 terminals. 3 if there's an existing cable which already carried E, N, and switched-live, e.g. the cable running to a non-loop-in ceiling rose you're replacing; 4 if you're using the JB to effectively replace an existing rose, or existing JB where switch-return wire feeds in.

With 4 cables to join (6 should you be replacing an existing loop-in rose!), I'd use a larger 30A JB, just to have a little more room to work in - with just the 4 terminals. One will common up all the Ns, one will join the switch-return/switched-live to the L of the three transformer feeds, one will join any perm-Ls you may have (switch feed, loop-in, loop-out, if that's what your JB is replacing). And the 3rd, or 4th, will be for your earth conductors.

NO. All the earth conductors should be properly joined at one of the JB terminals, should run through to the transformers, and if your transformers are Double-Insulated/Class-II, *and* the fittings themselves don't need earthing, you should sleeve the bared earth wire and secure it to the cable end with a few turns of insulating tape. That way, should you or a future householder refit with other fittings which do need an earth, it'll be ready and available, not cut off in its prime.

You're welcome - definitely better to ask ahead of time than the not-uknown post of 'I took a light fitting down, undid all the wires, then I joined all the reds together, and all the blacks. Now my fusebox goes "pop" every time I try to turn the lights on.'!

HTH - Stefek

Reply to
Stefek Zaba

Always terminate an earth rather than cut it off. You never know when you may need it in future.

Reply to
Dave Plowman (News)

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