20A Junction boxes take only 3 cables?
 

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

Aldrich wrote:

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.

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

Aldrich wrote:

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.

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

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

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

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.
--

SJW
Please reply to group or use 'usenet' in email subject

"Aldrich" wrote in
:

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


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

"Stefek Zaba" wrote in message
...
Aldrich wrote:

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.

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.

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.


--
Kevin Poole
**Use current month and year to reply (e.g. )***
Car Transport by Tiltbed Trailer - based near Derby

mike ring wrote:

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.

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