wiring advice

[al]

Dear me .. nothing's ever simple! All I wanted to do was take a fused spur from the ring mains where the switch for my boiler was so that I could power a light ....

I opened the "junction box" there and found it was a chocolate box strip of

6 blocks, with loads of what looks like 1mm cabling (I say looks like because I only tend to use 1.5 or 2.5mm). Really flexible stranded stuff rather then solid core. There are 5 of these T&E cables coming in.

I'm slightly confused however as to just what I'm looking at. All of the neutrals are connected in one block, but the earths and lives are in a varied configuration that's hard to follow (access beside the boiler is difficult and there's not a lot of slack in the wires). When I turn the switch for the boiler off, none of the cables are live any more. When I turn it on, two of the blocks are. Does this mean that the entire thing is just a switched spur? A cable also comes out of this junction to the heating controller unit, which accounts for two (along with the boiler switch).

Out of the other 3 cables, two come up from under the floor together and the other disappears into the wall behind. Don't have access to find out any more about their onward journeys!

What can I do here? My intention was (assuming this was a normal junction box), to add in a 2.5mm T&E spur to the junction to my fused box, then run

1.5mm T&E from that to the light switch.

a

[dennis]

Put the cover back and find a different connection point.

The power feed is unlikely to have to have much capacity as it should be off a fused unit somewhere and is probably fused at 3A or so.

The cables will have connections that include:

boiler on (input) HW on (output) Heating on (output) pump (output) mains (input)

They should be labelled (mine aren't either).

[d.]

boiler

Very carefully put the cover back on the junction box and hope you have not disturbed any cables in it.

What you have found is the wiring centre for your heating system, with wires going off to the room stst, tank stat, motorised valves, time clock, pump, boiler and any thing else that might control your heating system.

As you noticed the neturals and earths are joined in there resptive connectors all the other cables will be LIVE at some point in the heating cycle what ever colour the cable may be.

One crossed wire or one broken wire = no heating or hot water and a possible high bill to sort the problem.

I would strongly recamend you take your spur from some other point on your ring.

David.

[al]

Damn, damn, damn and quadruple damn! Too late to move my spur now, will have to plaster it in and paper over. Going to have to try and take up the floor underneath and extend down there.

As an aside - is it normal to use such low rated wire for all of these c.heating elements? Seems like the type you'd find inside a hairdryer!

a

[al]

There is a fused box beside it, quite possibly 3A (intelligently placed where it's next to bloody possible to get the fuse out, so I ain't gonna play with it now just to find out its rating!).

Shouldn't the spur feeding it all be in 2.5mm cable though ... ie. before the fuse?

a

[dave stanton]

Yes, CH takes very little current, its usually done in 1mm T&E.

Dave

[al]

*dreams of a world where he could knock his house down and start from scratch* ......

.. sigh

a

[dave stanton]

And no Part P either......

Dave

[dennis]

Normally yes. (But it doesn't have to be if an appropriate breaker is fitted in the circuit (e.g. in the consumer unit)).

It may be an appropriate place to take another feed from.

[al]

Where? The 1mm T&E that comes up to the fuse for the C.H.? Seems a little dodgy? Or do you mean look under the floor below it and see if it's a spur from the ring main? Consumer unit's nowhere near the kitchen if you meant to take a feed from there ..

a

[Christian McArdle]

Yes. 1mm cable is good for many times the 3A the central heating will be fused at, although it is probably 0.75mm or thicker flex, which will also be fine for those currents.

Christian.

[al]

Aha ... damn hidden cables! Took the cover off the fuse unit (by the boiler, not the CU) and found a 2.5mm T&E feeding it. Real pig to get to - had to reach about 50cm down the side of the boiler (the gap to the wall beside it being about the length of a normal electrical screwdriver!).

I did not enjoy that little piece of wiring. It was a hot enough day already and the boiler had just been on, so really sweating buckets leaning over it and reaching down along it! SERIOUSLY awkward getting the new 2.5mm T&E spur cabled up to the feed. That stuff can be pretty damned inflexible when it wants to!

Anyway, as originally intended, that new spur now comes into a 3A fuse box, with 1.5mm T&E running up to the light switch and again the rest of the way to the light fitting. Let there be light ......!

Thanks for all the help from everyone.

a