70 volt potential from appliances to earth

[Risteard]

It sounds as if the 'spurred socket' may have lost it's earth connection, but it also sounds as if the rest of "the socket circuit in the kitchen" probably is 'earthed'.

Kind Regards, John

I thought he said it happened on a number of sockets in the kitchen, but not in the rest of the house. Perhaps I misread.

 

[winston1]

Oh right, I didn't realise that. Yes, they sometimes run at the same time. No problems so far. Will that be an overload then?

The problem is that some double sockets are only rated at a total of 20 amps rather than the 26 amps that two large loads can take. Sadly you can't replace them with two singles either as you cannot put two singles on an unfused spur. Fusing the spur won't work either as the max fuse is 13 amps. Best to avoid running both at the same time.

 

[Albumen]

It seems I have a bit of a mess here then.

1. There is a double socket in the laundry which is, I think, on the ring main - it's on the ring main because there is a thick (4mm?) wire going in and one coming out.

2. Also come out of that double socket is a very short wire which goes to an FCU which feeds 2 exterior lights. This is OK, yes?

3. Also coming out that double socket is a single cable to a double socket. It's thinner than the ring main. The socket it's feeding isn't fused or anything. This isn't OK I think. Not sure why. I risk overloading the ring main? Or just overloading the spur?

Interested in solutions to bring this within spec and make it safe.

My issues:

It would be very difficult to alter anything OUTSIDE this room. Solid floors, all walls and ceilings are newly plastered and decorated. INSIDE the room a fair bit of freedom. Though there's an issue of getting cable through the worktop without making too much mess.

One of the sockets on the ring main is in use (boiler control) but the other is free. Presumably one of the appliances plugged directly into that would be optimal? And a second FCU for the other appliance?

 

[winston1]

It seems I have a bit of a mess here then.

1. There is a double socket in the laundry which is, I think, on the ring main - it's on the ring main because there is a thick (4mm?) wire going in and one coming out.

2. Also come out of that double socket is a very short wire which goes to an FCU which feeds 2 exterior lights. This is OK, yes?

3. Also coming out that double socket is a single cable to a double socket. It's thinner than the ring main. The socket it's feeding isn't fused or anything. This isn't OK I think. Not sure why. I risk overloading the ring main? Or just overloading the spur?

Interested in solutions to bring this within spec and make it safe.

My issues:

It would be very difficult to alter anything OUTSIDE this room. Solid floors, all walls and ceilings are newly plastered and decorated. INSIDE the room a fair bit of freedom. Though there's an issue of getting cable through the worktop without making too much mess.

One of the sockets on the ring main is in use (boiler control) but the other is free. Presumably one of the appliances plugged directly into that would be optimal? And a second FCU for the other appliance?

1. Wire sizes are measured in the cross sectional area of the copper. Rings usually use 2.5 sq mm. Can be larger but not needed unless the ring is exceptionally large. Measuring the overall sheath is almost meaningless.

2. That is OK.

3. A spur to a double socket should be 2.5sq mm. There is no need to separately fuse it.

Plugging one of the appliances into a ring socket would be good. These is no need for an FCU on the other. The plug has a fuse.

 

[EFLImpudence]

1. There is a double socket in the laundry which is, I think, on the ring main - it's on the ring main because there is a thick (4mm?) wire going in and one coming out.

If you are correct about the size, then it could be a radial circuit.

 

[Albumen]

Thanks. So an FCU and an unfused spur BOTH coming off the same ring main socket is acceptable?

I've just had yet another grovel around and managed to get the flex from the washing machine direct into the ring main double socket. It's not pretty but with some clips it won't look too bad.

If I sort out the unfused spur that seems to be giving me 70 volts from somewhere that will be OK for the tumble dryer? And I can run both together, one on the ring main, one on the spur.

There's nothing else heavy on this ring main. It's just for the extension, no electric fires or anything.

 

[Albumen]

If you are correct about the size, then it could be a radial circuit.

It's back to back with another socket. I mean there's another double socket on the other side of a single skin brick wall. That's where the wires are coming.

How can I tell if it's radial/ring?

The house was rewired 20 years ago. Though these parts are new and I think are new circuits. The consumer unit was new about 3 years ago, and this whole extension was rewired about the same time.

 

[EFLImpudence]

A radial circuit will stop at the last socket and not go back to the consumer unit.

 

[ban-all-sheds]

you cannot put two singles on an unfused spur.

Why not?

 

[EFLImpudence]

4mm² has seven strands in the L and N, 2.5mm² has only one.

Whatever it is, it does not affect your problem.

 

[winston1]

Why not?

Cos the regs don't allow it.

 

[JohnW2]

Cos the regs don't allow it.

Are you perhaps referring to some 'informative guidance' that comes with the regs?

Kind Regards, John

 

[winston1]

Are you perhaps referring to some 'informative guidance' that comes with the regs?

Kind Regards, John

Maybe, but it is often stated as fact on these forums. I was under the impression it used to be allowed but was later banned.

 

[JohnW2]

Maybe, but it is often stated as fact on these forums.

It is, but there is definitely no regulation which says anything at all specifically about what may and may not be connected to an unfused spur from a ring final circuit, other than it must be an accessory to BS1363.

Regulation-wise, one is therefore left with general regulations regarding cable sizes and protection. Provided that the installation method is Method C (CCC 27A) there is no reason why 2 x 13A sockets could not be supplied by a 2.5mm² unfused spur. Indeed, as is quite often discussed here, if one used 4mm² spur cable (the circuit being protected by a 32A MCB), one could (again assuming Method C) have an unlimited number of any type of sockets, provided the designer was satisfied that the 'point load' on the ring was unlikely to overload any of the ring cable for appreciable periods of time (the same consideration as when deciding where to locate sockets on a ring)..

As for why Appendix 15 gives the guidance that it does, one could not be sure without asking the author. Perhaps the most likley explanation is that that author, like many others, regarded the 'maximum rating' (hence 'maximum load') of a double socket as being 20A (whereas 2 x 13A sockets would be 26A) and is giving guidance that would apply with a cable having the minimum CCC allowed for a ring final (i.e. 20A). However, one can but speculate about that.

I was under the impression it used to be allowed but was later banned.

I do seem to recall that there has been a change in the guidance, and maybe it was once even a regulation. Secure can probably help you there.

Kind Regards, John

 

[Albumen]

Thanks for all the advice folks. Though must admitted getting a bit confused now. I'm going to assume (at least for now) that the 'first' double socket I have in this room is on a ring main. So my question:

1. Is it OK to have, as there is currently, a fused spur (for lights) AND an unfused spur (for the appliance double socket) coming from the same ring socket?

2. If a single socket is designed for 13 amps, why wouldn't a double be designed for twice that? On the spur this is. Though as I can get one of the applicances into the ring it looks like this might not be the 'out of spec' arrangement I thought, once the problem with the unfused spur is resolved.

Or if the regulations are 'open to regulation', what would you do, faced with my situation, in your own home?