13A socket off 32A radial (old immersion heater cable)

[koniosis]

Hi,

I'm looking for some advice. I'm boarding my loft, we previously had the immersion heater removed and a combi-boiler fitted in a different location. I've found the old immersion heater wiring (single wire, not a ring) and I want to use it for a double socket in the loft. Am I right that I can just connect a double 13A socket:

http://www.screwfix.com/prods/15747...ts/White-Moulded/MK-Range/MK-13A-2G-DP-Sw-Skt

to a back box: http://www.screwfix.com/prods/19307...White-Moulded/MK-Range/MK-2G-40mm-Moulded-Box

And I don't need an fused switch before the socket? This wire (looks like 2.5mm) goes straight to the MCB and has a 32A CB there labelled "immer heater", I don't believe anything else is on this wiring.

Thanks!

 

[Steve]

Its wrong if it IS a 2.5mm cable on a 32A MCB. The 2.5 can only handle 27 amps maximum - it should be on a 16 or 20 amp MCB. This needs sorting before anything else.

 

[koniosis]

Thanks for the reply Steve, I am probably wrong about the 2.5mm, the house was built in 1995 and this is the original wiring to the immersion heater that was in a cupboard in the hall (top floor, wiring coming down from loft). It is this wiring that I have found (it sitll goes to a switch in the cupboard with nothing connected).

I thought 2.5mm was the usual wire for mains? The other two ring mains in the house are on 32A CBs and I'm fairly sure that's all 2.5mm. Has this changed since the house was built?

Also, if the CB is the right rating and the wiring, is what I propose correct?

Thanks

 

[sparkwright]

Ring final circuits are usually wired in 2.5 mm and may be protected by 32 amp mcb because they are rings.

Immersion circuits are usually radial circuits ie not rings. They are usually wired in 2.5 mm and protected by 16 or 20 amp mcb.

If your immersion circuit IS protected by a 32 amp mcb, it would only be acceptable if wired in 4 or 6 mm (or greater) cable.

 

[koniosis]

Thanks Sparkwright. I will check the wire. But I assume it is correct as this was a new-build (Barrats) in 1995 and you'd like to think they'd get it right. If not I'll change the CB to a lower rating.

After that, is what I propose safe?

Thanks

 

[sparkwright]

Yes. Check the size of the cable.

If you need to extend the cable or add more sockets use the same size cable. Make sure the cable size is suitable for the mcb you use.

As this is a radial circuit you can add as many sockets as you like.

 

[koniosis]

Thanks for your help.

 

[Taylortwocities]

this was a new-build (Barrats) in 1995 and you'd like to think they'd get it right.

 

[koniosis]

Well, the wiring in the old immersion heater cupboard is a nightmare!! It has the radial wire going into a switch with a wire that would have gone to the heater cut off. This switch then has a spur from it, going into a blanking plate with a fuse, which then goes into a 2G surface mount box with blanking plate. Behind this 2G box are 3 sets of 4 core wiring (Lighting I assume) connected to white connection blocks with the wire from the fuse above connected in.

What on earth is this radial wire doing connected to the lighting ring, even if it is via a fuse?! In addition I can't see why it is needed, since there is no fuse in the blanking plate and all the lights work anyway.

Help!

 

[sparkwright]

May be wrong but your description sounds like central heating/boiler wiring.

Are you certain it is connected to the lighting?

 

[koniosis]

Sorry, I mean 3 core & earth.

 

[koniosis]

Nope, no confidence, wire just looks like lighting wiring. Considering this was the old heating system, your explanation sounds sensible. Given that, what would 3 sets of 3 core & earth be needed for in a central heating system. Now that the old boiler and immersion heater are gone, how can I make safe the left over wiring. Look like the plumber who changed the boiler and removed the tank just cut some of the wires and put the blanking plate back on.

Eeek!

 

[koniosis]

Could it have been for a pump, or valve? If that is the case then none of these wires are actually connected to anything anymore, but all 3 wires vanish into the wall. I don't like the idea of leaving disconnected wires floating in the walls, how would you normally deal with this type of disconnected wiring?

 

[GaryMo]

Ring final circuits are usually wired in 2.5 mm and may be protected by 32 amp mcb because they are rings.

And ring circuits sometimes have radials attached to them, originating from other sockets, junction boxes or the 32A protective device itself. They're also wired in 2.5mm2 conductors.

 

[sparkwright]

POSSIBLY one cable went to the roomstat
and
the other two went to the programmer.