Garage wiring options

[NeilPalfreyman]

I just bought a house that has what I think is some suspect wiring in the attached garage.

I would like to sort it out so am after some advice on the best and safest option.

Power usage out there will be low. A double 13A socket for a freezer and lighting.

The existing wiring is taken off of a spur from the kitchen (I assume from the kitchen ring not another spur, but I haven't confirmed this yet.)

Someone has drilled through the wall behind a socket in the kitchen and run a cable from this to a double switched 13A socket in the garage on the other side of the wall. All of the garage wiring - another socket and the lights are "daisy chained" from this spur using trailing flex plugged into the socket.

I want to put a proper switched light in there and move the 13A socket to a more convenient location. What's the correct way of doing this without creating too much work?

 

[PrenticeBoyofDerry]

Without creating too much work and if you only require the one double socket, I would suggest either extending the ring so the one socket in the garage is part of the ring, (note your comments, that the ring and spur need confirming). On the extended ring you can then put this double socket and a switched fused connection unit, the S/FCU can then be down fused and extended load side for lights, you could install an inline switch or use the switch on the S/FCU to operate the light.
Or you could replace existing double socket in garage with a 13A FCU, then connect the relocated garage socket to that and the from that socket go down the S/FCU process for the lights. This method would allow you to at least isolate the garage electrics from the house if anything became faulty within the garage, therefore preventing power loss in the house/kitchen.
Also note sockets are now required to be RCD protected, although you have an existing socket and the requirements don't cover work prior to 2008, it would be advisable to have this protection on any new cable that is buried and not mechanically protected in the garage and the socket outlet, easy solution is to use a RCD/FCU device. If 30mA RCD is already existing on circuit, then there is no for any further addition of this type of protection.
Those are two options I would consider, also I would then prove once you have done this work that the work you have done is safe to put into service, there are a number of visual inspections and tests to be carried out to confirm this.

 

[AndyPRK]

Or you could change the existing socket to a junction box. Move socket where you want.

Connect lighting up via 3A fcu.

 

[PrenticeBoyofDerry]

Or you could change the existing socket to a junction box. Move socket where you want.

Connect lighting up via 3A fcu.

Appendix 15:
Unfused spur: An unfused spur should feed one single/one twin socket only.
This maybe down to interpretation, but that could mean that any additional loaded accessories would not allowed.
Thoughts!

 

[AndyPRK]

Practically a light isn't going to be an issue.

And extending a ring though the Garage for a sake of a light isn't sensible is it.

 

[PrenticeBoyofDerry]

Practically a light isn't going to be an issue.

And extending a ring though the Garage for a sake of a light isn't sensible is it.

Practically! I am concerned with the requirements of BS7671, practical or not.

The most practical thing to do would be change the existing socket for FCU, this would be very similar process in terms of connections and ease of install to using the JB method, and would be compliant to BS7671.

Extending the RFC by using two accessories (double socket and FCU for light)
Is not that difficult.

 

[AndyPRK]

I think that is where we disagree with the
Purpose of this forum. I think it is more to do with advising people how to do things safely that are premitted under older regulations.
Rather than being complient with the latest regulations that an electrician has to work to.

 

[mfarrow]

Practically! I am concerned with the requirements of BS7671, practical or not.

I think we discussed this before and the appendices are not part of the regulations, and are provided for guidance.

The requirement best to describe is that you do not load any part of a ring circuit with >20A load.

The most practical thing to do would be change the existing socket for FCU

I would change the double socket for 2x FCUs (daisy chained together). One fused at 2A for lighting, and off to a lighting circuit, and the other fused at 13A going to whatever sockets are needed in the garage. That way you are unlikely to have a non-compliant load, plus if anything happens when working in the garage (e.g. a welder/compressor overloads the circuit) you still have lighting.

 

[PrenticeBoyofDerry]

I think that is where we disagree with the
Purpose of this forum. I think it is more to do with advising people how to do things safely that are premitted under older regulations.
Rather than being complient with the latest regulations that an electrician has to work to.

I think advising anyone to do electrical work that is non-compliant should be frowned upon, if i were to ask a tradesperson for advice, I hope hope they would advise me to current standards not historically ones.
You seem to suggest that it is only electricians that need to be electrically compliant, I do not think that is why the standard is strictly there for!
Now then how long is it since spurring from a spur on a RFC has not been permitted?

 

[mfarrow]

Now then how long is it since spurring from a spur on a RFC has not been permitted?

It was "not permitted" a couple of decades ago, however that's not what the regulations say anymore. Now it's all about load.

 

[PrenticeBoyofDerry]

I think we discussed this before and the appendices are not part of the regulations, and are provided for guidance.

I don't think I was part of that particular discussion, that is why I added thought on my post.

The requirement best to describe is that you do not load any part of a ring circuit with >20A load.

True guidance but the only real guidance available, I accept >20A loading on an RFC but then we could consider two 13A plugged in loads and then additional lighting would exceed that.

I would change the double socket for 2x FCUs (daisy chained together). One fused at 2A for lighting, and off to a lighting circuit, and the other fused at 13A going to whatever sockets are needed in the garage. That way you are unlikely to have a non-compliant load, plus if anything happens when working in the garage (e.g. a welder/compressor overloads the circuit) you still have lighting.

I can see the logic in that.

 

[EFLImpudence]

Surely the restrictions regarding spurs are more to do with overloading the spur wiring.
I.e. preventing more than 26A on 27A conductors.

After all, there is nothing that could be connected on a spur that could not be connected directly to a ring at the same point.


If anyone thinks that anything can be 'designed correctly' on a ring, then advise the use of 4mm² for spurs.

 

[JohnW2]

Or you could change the existing socket to a junction box. Move socket where you want. Connect lighting up via 3A fcu.

Appendix 15: Unfused spur: An unfused spur should feed one single/one twin socket only. This maybe down to interpretation, but that could mean that any additional loaded accessories would not allowed. Thoughts!

Most electricians seem to interpret App 15 in that way - but, of course, it is only 'informative' (i.e. 'guidance'). Ironically, the actual regulation which allows ring finals specifically allows unfused spurs, without any qualification/restriction, but doesn't even mention fused spurs! As EFLI has said, the only bit of the actual regulation (433.1.103) that is really relevant is the bit that says that a ring final circuit should be designed such that "...under the intended conditions of use, the load current in any part of the circuit is unlikely to exceed for long periods the current-carrying-capacity (Iz) of the cable.".

In common sense terms, it certainly seems very odd that App 15 (even though it is not mandatory) appears to say (and is usually interpreted as saying) that one double socket on an unfused spur is OK, but two single sockets (or, say, a single socket plus FCU) aren't. However, it's probably reasonable to feel that if one went beyond two 'socket outlets' (one double or two singles) then it could sometimes be difficult to be certain that the cable was never going to be overloaded.

However, the reg talks about "under intended conditions of use", which allows the designer/electrician a fair bit of discretion. If, as may often be the case, it is clear that there are several sockets arranged around a room (say garage) just 'for convenience' and that it would be very rare for more than one of them to be used simultaneously for significant loads, then I think a designer could reasonably design a multiple-socket unfused spur without being non-compliant with 433.1.103.

As for lighting, I would imagine that most people would have to agree that adding a little lighting to an unfused spur supplying one double socket was not, in reality, going to make a blind bit of difference to the probability of the circuit's cable being significantly 'overloaded for long periods' - so, again, arguably compliant.

IMO, the 'problem' is that many feel that, since it exists, the 'safest' thing (in terms of their backsides) for them to do it to stick to the word of the guidance in ('informative') App 15, since there is then no risk that they would be called upon to justify their design in terms of the regulations themselves.

Kind Regards, John

 

[mfarrow]

Apologies, yes, the limitation is ccc of course with a minimum stipulation that it shall be 20A, not that the load shall not be >20A. Although in most existing circuits where parts of the cable route are not known, it may be prudent to assume a ccc of only 20A.

The whole regulation is, of course, made slightly pointless by 433.3.1 (ii).

 

[JohnW2]

The whole regulation is, of course, made slightly pointless by 433.3.1 (ii).

... as recently discussed at considerable length

However, I'm not sure that's really applicable to what we're discussing. If there is already a double socket on an unfused spur, and particularly if one works to what you just wrote about assuming a worst case (minimum permitted by 433.1.103) cable CCC of 20A, then the spur cable could theoretically already be loaded 'to its limit' by the loads plugged into the socket (unless one knew, for sure, that only low loads were ever going to be plugged into it). I'm therefore not certain that one could really argue that adding anything further (lighting or whatever) to the circuit would be unlikely to cause the cable to carry an overload current. Indeed, if the socket were already providing 20A, and the CCC of the cable were 20A, then, technically speaking, it would be inevitable that any further load would cause the cable to carry an overload current.

That's per the regs but, as I said, adding a little lighting to an unfused spur is, in reality, not going to make a blind bit of practical difference to anything!

Kind Regards, John