20A Junction boxes take only 3 cables?

[Aldrich]

Hi

I am rewiring the upstairs lighting circuit of our house. I have chosen to use 1.5mm 6242Y cable. I want to use the junction box method rather than the loop-in method because I find it a pain trying to get three cables into a ceiling rose. The junction box method requires 4 cables (switch, light, loop-in and loop-out) per box and the books I have read suggest that it is typical to connect 4 cables to a junction box.

However, I have just discovered that the "standard" 20A junction boxes that I have bought are only rated for 3 x 1.5 cables. One solution is to use two junction boxes, one to handle the loop-in/out and the other to handle the local lighting circuit. However, that seems a little inelegant and costly on boxes.

Please can someone comment on the limitation of 3x 1.5 cables per box and suggest a solution?

Thank you

David

[Lobster]

You didn't mention how many screw terminals there are in your junction boxes. If there are only 3 (which sounds likely if it specifies only 3 cables can be connected) then you've got the wrong jct boxes; if there are 4 (ie, which you need for the jct box method) then I'm stumped because you that would normally presuppose you will have 4 cables entering the jct box (unless it's the final one on the circuit, when there would only be 3).

There are presumably cut-outs on the side of the junction box enabling different numbers of cables to enter, depending on the orientation of the lid; there are usually little diagrams showing the orientation for

1, 2, 3 or 4(?) cables entering - do you have this?

David

[Stefek Zaba]

In what way "rated"? Do you mean it's hard to reliably secure four

1.5mmsq cores in the terminals provided? Or that the covers seem to have only three exit positions? Or some other problem?

If the first - no-one's stopping you using 30A-rated JBs, and I find the extra space in those is usually a Win for my fat fingers.

If it's cable entries you fell you're short of, most circular JBs I've seen have extra depth available on the existing positions, by knocking out an extra section of the entry; it's possible that the ones you have are supplied with say 3 entries premade, but a knockout for another entry elsewhere. The JBs I'm familar with have Cunning rotating covers and little marked positions to support 2,3, or 4 entries used, with two "2-entry" positions (one at 90degrees to each other, the other at 180).

If some other problem - shout.

HTH - Stefek

[Lurch]

On Thu, 30 Dec 2004 17:06:34 -0000, "Aldrich" strung together this:

It means 3 x 1.5 cables per terminal. You will have 4 terinals in a

20A 4 terminal box.

3 lives in the 'loop'

3 neutrals. 2 in the switched live. And finally, 4 x 1mm earths.

There you go, problem averted.

[mike ring]

"Aldrich" wrote in news:41d435fd [e-mail]:

One solution is

I think saving on J/B's is a snare and a delusion. Where do you want all this elegance anyhow? In the loft, or under the floorboards?

I agree with Sefan, use bigger ones for ease of use which will help achieve more reliable connections.

Lurch described how you don't normally use more than three cables.

I was brought up to follow the golden rule "one in, one out, one away" and not to bodge further connections in, for all sorts of things from tag blocks to frame rooms.

If you need to get more in, say with wall lights, gather the lights in one (or more) J/B'z and then bring in the switched circuit from the "rose" box.

IMO far more elegant, the purpose of each box can be marked on it, maybe more boxes, but *elegantly* hooked together. Form follows function.

Thats wot I fink anyhow

mike

[Autolycus]

One small word of caution, in case someone less clued than the OP reads this: a default 30A junction box is often a three-terminal one. Screwfix sold (still sell?) some truly vile white 4-terminal boxes which limited their cable capacity by using badly designed or made grub screws - a long plain section beyond the thread meant that you could only unscrew them a couple of turns before they fell out. Once you'd retrieved them from the underfloor fluff you could always file them down, and then discover that the brass insert was so flimsy that it spread and let the screw pop out again as soon as you tightened it.

[Lobster]

I must be being dense but I don't follow... When I do this I would normally have daisy-chained junction boxes, with usually four cables per box, ie power arriving from previous box, switch cable, cable to light fitting, and power leaving to next box. How do you do it with three cables?

David

[John]

Interesting what combination of cables would require a 6 term standard JB then

[mike ring]

Lobster wrote in news:MB0Bd.2176$Gv.1497 @newsfe1-win.ntli.net:

He was talking about terminals - the "cables" must have been a slip of the pen, and I did not wish to pedantically correct it ;-)

Four candles, er, cables, but on the four terminals

1 L in from last box, out to next box, live to switch. 2 N ditto , ditto , neutral to lamp 3 switched live , switched live to lamp 4 4 earths (well, it's a "good" rule, not necessarily unbendable)

mike