Installing extra appliance, electric supply advice needed

[JohnW2]

One could say that. However, the requirements relate to 'the circuit' and I would have thought that most people (even the BS7671 definition!) would say that spurs were part of 'the circuit'. wouldn't they?

Spurs are obviously part of the circuit but not part of the ring. ... Does the wording not say that "ring circuits must be done like {the following} whether or not there are spurs".

There clearly are various ways in which the wording could be interpreted.

I cannot see why the spurs, especially the without spurs part, are mentioned at all.

That's what we're discussing, isn't it? The spur cable to a double socket is being protected upstream by a 30/32A OPD (which would never be sufficient) and downstream by two plug fuses, both of which could be 13A (i.e. 26A total) - and the latter would not be adequate if the CCC of the spur cable was as anything like as low as the minimum permitted for the cable of the ring. Is it perhaps your belief that an unfused spur cable supplying a double socket must have a CCC of at least 26A (i.e. that 2.5mm² would only be acceptable if 'clipped direct')?

This whole sub-discussion arose because, in commenting about the total load capacity of a double socket, I 'innocently' suggested that (assuming it also applied to unfused spur cables!) the 20A minimum CCC for rings would be consistent with a view that a double socket was considered as a maximum load of 20A.

No electrical reason, really (given the downstream ≤13A fuse in the plug) - so maybe this is another example of a 'lack of exhaustiveness' in Appendix 15.

I suppose not every option can be shown but a noted box, as with the other options, could be included.

Quite so - you have already used the fact that ('guidance') App 15 is non-exhaustive to support your view that a 4mm² unfused spur (from a 2.5mm² ring final) supplying two or more sockets would be compliant (we don't disagree that it is certainly electrically satisfactory).

Kind Regards, John

 

[EFLImpudence]

I cannot see why the spurs, especially the without spurs part, are mentioned at all.

That's what we're discussing, isn't it? The spur cable to a double socket is being protected upstream by a 30/32A OPD (which would never be sufficient) and downstream by two plug fuses, both of which could be 13A (i.e. 26A total) - and the latter would not be adequate if the CCC of the spur cable was as anything like as low as the minimum permitted for the cable of the ring.

Does that not confirm that the requirements do not apply to the spurs?

Is it perhaps your belief that an unfused spur cable supplying a double socket must have a CCC of at least 26A (i.e. that 2.5mm² would only be acceptable if 'clipped direct')?

I would think, as it is expected that that will be the case (because people will), that a CCC of 26A should be fitted.

This whole sub-discussion arose because, in commenting about the total load capacity of a double socket, I 'innocently' suggested that (assuming it also applied to unfused spur cables!) the 20A minimum CCC for rings would be consistent with a view that a double socket was considered as a maximum load of 20A.

I think that is extremely unlikely and it is not going to be the case in real life.

 

[JohnW2]

Is it perhaps your belief that an unfused spur cable supplying a double socket must have a CCC of at least 26A (i.e. that 2.5mm² would only be acceptable if 'clipped direct')?

I would think, as it is expected that that will be the case (because people will), that a CCC of 26A should be fitted.

"Should" probably being the crucial word there. I would imagine that there must be an lot of unfused spurs out there which go through insulation or are in conduit etc. - but have you ever seen 4mm² cable used for an unfused spur (from a 2.5mm² ring final) for that reason?

Kind Regards, John

 

[EFLImpudence]

have you ever seen 4mm² cable used for an unfused spur (from a 2.5mm² ring final) for that reason?

I have not.

 

[JohnW2]

have you ever seen 4mm² cable used for an unfused spur (from a 2.5mm² ring final) for that reason?

I have not.

As you will realise, that doesn't surprise me

However, would I be right in guessing that you probably have seen unfused spurs feeding double sockets for which the spur cable CCC, after de-rating, was less than 26A?

Kind Regards, John

 

[EFLImpudence]

Yes, in conduit. I don't recall because of thermal insulation.
Perhaps because of the wording we have been discussing.

To be realistic, because of the safety margins, it probably doesn't matter.

 

[JohnW2]

Yes, in conduit. I don't recall because of thermal insulation.

Fair enough.

Perhaps because of the wording we have been discussing.

Perhaps, although I'm not convinced about that.

To be realistic, because of the safety margins, it probably doesn't matter.

Of course. That's why you and I, and I'm sure many others, are not 'personally concerned' in the slightest about these sort of issues. However, we're talking about regs, rather than what we are 'personally happy with' - and I suspect that many electricians feel constrained to be strictly reg-compliant, whatever their personal views/feelings. Mind you, I wonder how many of them have put in an unfused spur, through conduit to a double socket and not even thought about the fact that the 2.5mm² cable they used was 'inadequate'! Or perhaps, if they are 'BGB-obsessed', they do think, but take the fact that App 15 shows 2.5mm² unfused spurs, without any mention of CCC or de-rating factors, to mean that it is OK

Kind Regards, John

 

[Smiffy7]

Wow! I wasn't quite expecting the intense debate that followed my original post - thanks to all for your comments and suggestions. Not being an electrician I'm not going to even try and join the debate!

I hope you will sympathize that I got rather swamped reading through the thread and all the potential solutions to my problem kind of got lost. Was it ever agreed as to the best solution?

Just to remind you, I'm looking for a solution without having to remove tiling; I'm happy to do some re-wiring, changing of switches etc. Also, as long as the solution is electrically sound and safe, I'm not too bothered if the regs do not specifically permit the solution in black and white.

Thanks again

 

[deadshort]

I think i gave you that. 20a is the maximum load that uk double sokets are designed to operate at. Add the total load of the DW and WM together that's the maximum power they would require assuming both heating elements were in use at the same time ,how often will that happen ?

It is perfectly acceptable to wire a double socket as an unfused spur via a 20a switch if you wish.



Regards,

DS wait for the next twenty plus pages

 

[Smiffy7]

I think i gave you that. 20a is the maximum load that uk double sokets are designed to operate at. Add the total load of the DW and WM together that's the maximum power they would require assuming both heating elements were in use at the same time ,how often will that happen ?

It is perfectly acceptable to wire a double socket as an unfused spur via a 20a switch if you wish.



Regards,

DS wait for the next twenty plus pages

Yes you did suggest that - thanks - but there have been many other suggestions so I was just wondering if it was agreed as to which is the best solution?

Only thing about your solution I wasn't sure about - using a 20A DP switch, would the total load of a WM & DW not exceed 20A?

Assuming then that this solution is electrically sound it does seem the most straight forward:

1) I need to swap my existing FCU (one of these http://www.screwfix.com/p/13a-switched-fused-connection-unit-spur-white/2323d) with a 20a DP switch (one of these http://www.screwfix.com/p/british-general-20a-1-gang-double-pole-switch-white/76090)

2) I then need to swap my existing 1-gang un-switch socket under the worktop with a converter socket (one of these http://www.screwfix.com/p/clipsal-converta-socket-1-gang-to-2-gang-polycarbonate/12849)

3) Re-use all existing 2.5mm T&E cabling

Have I interpreted your solution correctly?

I take it both of the above swaps are simple straight swaps in terms of fitment?

Presumably then, there is no solution out there where I can fit a 2-gang switch above the worktop with 2 separate spurs to individual sockets below?

Sorry for going over old ground, but as I said, I got kind of swamped in the debate!

Cheers

 

[JohnW2]

I wait for the next twenty plus pages

We can hopefully avoid that by leaving it to you to give ongoing advice to the OP.

Kind Regards, John

 

[Smiffy7]

I wait for the next twenty plus pages

We can hopefully avoid that by leaving it to you to give ongoing advice to the OP.

Kind Regards, John

How come John? Was it you who suggested using 4mm2 cable? Would this make the above solution even better/safer?

 

[JohnW2]

I wait for the next twenty plus pages

We can hopefully avoid that by leaving it to you to give ongoing advice to the OP.

How come John?

Because I suspect that some electricians might have different opinions.

Was it you who suggested using 4mm2 cable? Would this make the above solution even better/safer?

It wasn't me who first suggested it. It was really just an attempt to find (I'm not convinced totally successfully) a way of remaining regulations-compliant if you wanted to feed two single sockets (rather than one double socket) as an unfused spur. An unfused spur consisting of 2.5mm² cable supplying one double socket is fine, both electrically and regs-wise, although there would be no harm in using 4mm². The only real debate, where you are likely to find differing opinions, relates to the wisdom of supplying two 'large kitchen appliances' from one double socket (as opposed to two single sockets).

Kind Regards, John

 

[deadshort]

Hi, yes what you suggest is fine. My mothers house which was built in 1999 has exactly what you have the only difference is she has 20a DP switches instead of FCU's. When she moved out of the house we discovered that the DW and WM where plugged into the single socket with a 4 way extension lead under the plinth ! It worked for years with no problems.

If you washing machine has a hot water intake that's even less likely to be on a boil wash !

My original suggestion was a 32a switch which will give you plenty of connection space and a good quality one has 2 sets of screw terminals.

I stay clear of the cheaper Con-verta sockets and buy a 1gang to 2 gang conversion box and use an MK or Crabtree socket.

This is a tile save solution. The only other option is an additional socket supplied from below


Regards,

DS

 

[JohnW2]

If you washing machine has a hot water intake that's even less likely to be on a boil wash !

AIUI, machines with hot water intakes have become a 'historical curiosity'. Modern machines seem to wash things in such a small puddle of water that, unless there is a nearby combi-boiler, the machine's requirements are often satisfied by the amount of cool/cold water in the pipework from the hot cylinder, so that all is achieved by having a hot inlet is to draw hot water into the pipework, to subsequently cool and, at least in summer, represent 'wasted energy'! ... well, that's the explanation I was given when I asked why hot inlets seemed to have virtually vanished!

Kind Regards, John