how many wires can go into a lighting 20amp junction box

[cookiemonster1]

Hi in my loft there are a few heavy duty 20amp junction boxes for the lighting circuit with about six wires going in. Is this okay as far as safety and regulations are involved?

 

[Steve]

If its neat and tidy, all the wires clipped down, yeah i dont see why not.

Thats been there near on 20 years. It controls two lights and seems to be the main hub for the upstairs lighting.There is an aditional JB further down the loft, that is it. The little JB seems to be for the loft light, added later.

 

[securespark]

As long as they are all the same kind of wire (ie not mixing fixed wiring & flexible cables) and the conductors are all securely clamped by the screw, I can't see too much of a problem.

Also, make sure all cables are clipped up & junction boxes themselves screwed down.

If the usual junction box lighting system has been employed, there are only 4 cables in any JB: feeds in and out, a switchwire & a switched feed to a light fitting.
But there can be many variations on this: an extra feed out to another light fitting or a shaver unit for example, an extra switched feed to a second fitting etc..

Some junction boxes say on the bottom how many conductors of whatever size they can accept. This should not be exceeded as the terminal will then be overloaded, giving the possibility of poor continuity & in the case of some cheap JB's, crossed threads.

 

[securespark]

Oh, poo. All that time I spent typing a reply and you snuck in and beat me...

 

[JohnD]

incidentally, there are little 6A JBs made for lighting circuits, but they are ridiculously small and weedy and difficult to cram wires into the tiny terminals.

Using a 20A one is far more roomy and eaay to use. The extra cost is trivial.

 

[cookiemonster1]

Thanks for the replies. The junction boxes do say max 4 x 1.5mm cables on the bottom but everything is secure and screwed down. Shall I alter the wiring to fit 4 cables?

 

[mattylad]

I havn't seen it mentioned so better for anyone else reading wot duz not know...

"As long as the total load is no more than 20A".

A "20A junction box" kind of gives that away, but I thought it worth mentioning.

(your unlikely to have 20A used on a lighting circuit, but they have been used on final Rings before & shouldn't be).

 

[Space cat]

The junction boxes do say max 4 x 1.5mm cables on the bottom

Six wires of 1 sq mm each is the same amount of copper as four 1.5 sq mm wires so, unless some of your cable is 1.5 sq mm, six in a terminal is OK. In fact they will fit more readily than four bigger ones.

 

[ban-all-sheds]

Thats been there near on 20 years.

Since before the cleaner last visited.

Look at the state of it.

You should be ashamed.

 

[Steve]

Thats been there near on 20 years.

Since before the cleaner last visited.

Look at the state of it.

You should be ashamed.

I know, we have a cleaner, but we must not pay her enough to do the loft. Mind, she is 80, i dont think ladders are her strongpoint, though she did clean the gutters the other day, after she'd done my spark plugs and mowed the grass.