New sockets in garage

[flameport]

1. I'll be creating a new ring main for the loft sockets and running these off the spare 32A breaker on the consumer unit. Can I include the two new "downstairs" sockets on this same ring main or should they be installed as spurs from existing downstairs sockets. It would be easiest to put them on the new "upstairs" ring that the loft sockets will be on, but is that against the regs and/or a bad idea?

Either option is fine, but why the need for a new 32A circuit?
What loads will be used on this new circuit - 32A is over 7kW.

2. For the wiring in the loft, is it a requirement (and/or a good idea) to use conduit/trunking or is it ok to simply clip 2.5mm T&E cable to the walls and roof timbers?

Again either option, surface clipped is fine provided there is no risk of the cables being damaged by objects etc.
If the loft is like most, and will be stuffed with junk, then conduit or trunking would be desirable.

3. If mechanical protection is needed, would trunking or conduit be the preferred choice? Is one going to be easier than the other in terms of threading cables through, going round corners, t-eeing off to downstairs sockets etc?

Round conduit would be my choice, but trunking could be used. 20mm will be fine for most applications, unless you have an excessive number of wires/cables.
25mm conduit will also require larger socket boxes, as the standard ones are not deep enough.

The PVC boxes are designed for use with conduit, as they already have 20mm knockout holes in them, and if not, additional holes can easily be drilled where required.
The 'normal' ones are useless for conduit, as they are far too brittle and will shatter into pieces if you attempt to drill holes in them. Even if you somehow managed to get a round 20mm hole in one, you will then find the plastic is too thick to accept the conduit adaptor.

 

[autolycus]

As for your question (2), there is no requirement for any conduit/trunking unless you feel that conduit is necessary to protect the cables from particular risks of mechanical damage. If there are no such specific risks, clipping T+E to walls, roof timbers etc. is perfectly acceptable.
As for your Q's (3), (4) and (5), they become moot unless, per (2), you feel that mechanical protection is necessary. If you did decide that it was necessary, it would probably have to be conduit - trunking affords little mechanical protection, and is really only used for aesthetic reasons.

The person is already on board. ... In an effort to steer this topic back to my original questions and away from discussions about who can/can't do the work, I'm going to rephrase my original post as follows:

I've just answered your original questions. To save me reading/re-thinking, are these re-phrased questions significantly different?

If, as you say, you already have a Third Party Certifier on board, then (s)he is the person you really should be asking the questions, since (s)he is the person who has to decide whether they are happy to certify the work.

Kind Regards, John

Thanks, John. Re-phrased questions were the same but without reference to a new ring.

The TPC recommended mechanical protection in the loft space on the basis that it wouldn't add much to the overall cost and reduced the risk of any damage from, for example, mice.

 

[autolycus]

1. I'll be creating a new ring main for the loft sockets and running these off the spare 32A breaker on the consumer unit. Can I include the two new "downstairs" sockets on this same ring main or should they be installed as spurs from existing downstairs sockets. It would be easiest to put them on the new "upstairs" ring that the loft sockets will be on, but is that against the regs and/or a bad idea?

Either option is fine, but why the need for a new 32A circuit?
What loads will be used on this new circuit - 32A is over 7kW.

Minimal. It's going to be powering a network switch and a couple of IP cameras.

2. For the wiring in the loft, is it a requirement (and/or a good idea) to use conduit/trunking or is it ok to simply clip 2.5mm T&E cable to the walls and roof timbers?

Again either option, surface clipped is fine provided there is no risk of the cables being damaged by objects etc.
If the loft is like most, and will be stuffed with junk, then conduit or trunking would be desirable.

There's minimal junk in there - that's all in the loft of the house! The electrician I spoke to suggested conduit was needed because the cable was potentially at risk from human or rodent damage if it was just clipped.

3. If mechanical protection is needed, would trunking or conduit be the preferred choice? Is one going to be easier than the other in terms of threading cables through, going round corners, t-eeing off to downstairs sockets etc?

Round conduit would be my choice, but trunking could be used. 20mm will be fine for most applications, unless you have an excessive number of wires/cables.
25mm conduit will also require larger socket boxes, as the standard ones are not deep enough.

The PVC boxes are designed for use with conduit, as they already have 20mm knockout holes in them, and if not, additional holes can easily be drilled where required.

Oh, I see. So they allow the conduit to actually go into the box rather than butting up against the outside of it, right?

 

[flameport]

If the load is minimal, forget the new circuit, and the third party certifier / notification.
Just add the sockets to the existing circuit.

Yes, the round conduit fits into the box, using one of these: http://www.toolstation.com/shop/d190/p91534
Adaptor fits into 20mm hole, conduit fits into the adaptor.

 

[JohnW2]

Thanks, John. Re-phrased questions were the same but without reference to a new ring. ... The TPC recommended mechanical protection in the loft space on the basis that it wouldn't add much to the overall cost and reduced the risk of any damage from, for example, mice.

If you continue to use a TPC, there's really no downside of a new ring, even if it's probably not necessary!

As I said, there has to be a judgement about the need for mechanical protection - but plastic trunking or plastic conduit would afford little protection against gnawing rodents (particularly rats, which are the usual culprits, not mice!) - only steel conduit would protect against them. Many/most loft spaces are full of wiring (for other circuits, as well as any 'loft ones'), particularly lighting circuits of the floor below, and the cables are very rarely put in conduit. However, there's nothing to be lost (apart from a lot of extra work, if you use steel conduit - which needs special tools/skills etc.) by using conduit if you want to. Also, if the TPC is 'recommending' conduit, does that mean that(s)he might be hesitant to certify the work if you don't use it?

Also, as flameport has just written, if your load is small then it would make sense to just extend the existing sockets circuit and 'sack' the TPC, and hopefully save at least some of what (s)he would be charging you.

Kind Regards, John

 

[autolycus]

Some don't like the idea, and there may be an issue with putting four conductors into a socket terminal, but there is no regulation which says it is a no-no. There is always also the possibility of inserting junction box(es) into the ring to provide one or more of the spurs - again not idea, but not only allowed by the regs but actually illustrated as an example in an Appendix of the regs..

Well I never knew that. So (provided you can cram four cables into the back on one socket) you can spur two double sockets off one existing socket on the ring, but you can't spur off from a spur (i.e. daisy chain). Have I got that right?

 

[JohnW2]

Well I never knew that. So (provided you can cram four cables into the back on one socket) you can spur two double sockets off one existing socket on the ring,

Yes, essentially that. However, it's not necessarily only a question of being able to 'cram in' four cables. If the manufacturer of the socket says that it only "has capacity for" three cables, then by using four you would be failing to comply with the manufacturer's instructions.

...but you can't spur off from a spur (i.e. daisy chain). Have I got that right?

Indeed, and the reason is simple enough. With a standard 2.5mm² ring circuit, the 2.5mm² cable of a spur is adequate to supply one socket, but not necessarily adequate to supply more than one, as would happen if one 'spurred from a spur' (since the cable from ring to first spurred sockets would be carrying both the current from that socket and current from the one that was spurred from it). That problem doesn't arise if two or more spurs, each supplying only one socket, originate from the same point on a ring.

Kind Regards, John

 

[ban-all-sheds]

But in this particular case, the fact it is notifiable won't cause any extra hassle or expense.

How come, given that TPCs don't work for free?

In an effort to steer this topic back to my original questions and away from discussions about who can/can't do the work.

It's an important discussion.

Because you can't - you don't know enough, as is obvious from the questions you are asking. There's nothing wrong with questions per se, or with improving your knowledge that way, but it is abundantly clear that you're attempting to do electrical design work on the basis of asking questions as you go along about things you realise you don't know but need to. That is a deeply flawed approach, because it assumes you have no unknown unknowns. It assumes that you won't fail to ask about something you don't know because you have no idea that it exists and that you need to know it.

You've given yourself excellent proof of that:

Well I never knew that.

Indeed not. But that wasn't something you asked about - it just happened to come up.

Do you see the problem? How do you know there's nothing else that you are not asking about because you don't realise you don't know it?

And as JohnW2 pointed out - your TPC will have to sign your work off - you need to be asking him what he wants to see done, not us.

 

[ericmark]

I have read questions and answers and first point is I don't see a location England, Wales, and Scotland all have different rules it would seem from answers people are assuming you live in England other wise 90% are wrong.

Although the garage may have a 32A MCB that does not mean it should have a 32A MCB and first things first you need to check the supply to the garage. There are a number of ways a supply can be taken to the garage most common is from a MCB in the house. I have seen where the supply is from a 20A MCB in house in 2.5mm² cable but in the garage there is still a 32A MCB simply as it was in the box as supplied rather than being the correct size. It does not really matter as still protected but could affect the design so that needs to be first check.

I have looked for third party inspectors and oddly found some even in Wales where they can't actually do third part inspections but also noted most were not electrical only firms but had a different main business and it would seem they are using the ability to allow other trades to complete some of the electrical work then their inspector can sign it off. Although they could it would seem they are not really interested is signing off work outside the company. For years the LABC inspectors have been taking a chance and as yet it would seem they have not been caught out. However the well publicised Emma Shaw case does highlight the problems of being an inspector and so I can understand why any inspector will now tend to go OTT in what they require.

As a result it can some times work out cheaper to get a scheme member electrician to do the job than DIY.

The other problem with DIY is inspection and testing it does not matter if LABC or TPC they will not complete an electrical installation certificate you need to do that. They can and do issue completion or compliance certificates without having an EIC but then you still have a problem on sale of no EIC. Only the person doing the work can sign an EIC.

It also does not matter how many questions you ask on here and how good the answers are it is all down to the person issuing the completion or compliance certificates and know one else.

If however you have no intention of getting a completion or compliance certificate then the answers are very different. If the rules are broken then there is a problem that an EICR could highlight them so really you do need to follow the rules even if your not getting the legal paperwork completed. As to rodent attack one needs to do a risk assessment clearly a farms barn has a much higher risk than a domestic dwelling and the location of local ponds and shops will also affect the risk. Only some one local can really assess the risks.

There are plug in testers like the EZ150 which will highlight many faults but not all. To detect a reversed neutral - earth is hard but with RCD protection it is unlikely to allow you to set the RCD so in real terms unlikely to go unnoticed. Since all new sockets need RCD protection you will need it either in house or in garage. I have not noted how you are installing RCD protection that also could change the design.

Using duel socket box you can get extra connections without exceeding the three wires per terminal also using the grid system and a 4 modular plate with two sockets does the same thing. This can also be used to house RCD FCU if that's the way you go. But since at the moment I don't know what RCD protection you have no point in going further.

 

[ban-all-sheds]

it would seem from answers people are assuming you live in England.

So is he, for if he were not then he would not be planning to use a TPC, who is already engaged.

 

[AndyPRK]

Good point Eric about the MCB size in the house.

 

[riveralt]

Some don't like the idea, and there may be an issue with putting four conductors into a socket terminal, but there is no regulation which says it is a no-no. There is always also the possibility of inserting junction box(es) into the ring to provide one or more of the spurs - again not idea, but not only allowed by the regs but actually illustrated as an example in an Appendix of the regs..

Well I never knew that. So (provided you can cram four cables into the back on one socket) you can spur two double sockets off one existing socket on the ring, but you can't spur off from a spur (i.e. daisy chain). Have I got that right?

It does seem to me that you are fixated on a certain electrical design plan - that would ultimately be costly and probably illegal under current legislation.
Flameport (JohnW2) have suggested an alternative that is both cheaper and legal.
So I will repeat:
If as it seems you have a ring final circuit in your garage and accessible wiring then interrupting the ring and adding the required sockets for the garage is the simplest method.
For the loft area you can spur upward from any of the garage sockets to a single double socket in the loft area.
Alternatively, given your projected load, run a single 2.5mm² T&E from one of the garage sockets up to the loft and into an FCU (or preferably an RCD/FCU) then run you radial circuit around the loft area.
The type of conduit depends on a risk assessment for the loft area.

 

[autolycus]

Thanks flameport and JohnW2 for your helpful comments. I went with your suggestion and did all the new sockets as spurs. All working a treat.

 

[Iggifer]

Yes, essentially that. However, it's not necessarily only a question of being able to 'cram in' four cables. If the manufacturer of the socket says that it only "has capacity for" three cables, then by using four you would be failing to comply with the manufacturer's instructions

Not strictly relevant, but that's par for the course around here, but an MK K770 2amp round pin socket is rated for 7, yes that's seven 1.0mm cables per terminal. I would NOT want to see inside that box or anything else wired by someone that had to get 7 cables into one point on the circuit

 

[JohnW2]

Not strictly relevant, but that's par for the course around here, but an MK K770 2amp round pin socket is rated for 7, yes that's seven 1.0mm cables per terminal.

Indeed so - but there again, the corresponding 15A round pin socket (MK K772) is 'rated' only for 3 x 2.5mm² conductors (or 3 x 4mm² ones!). There doesn't seem to be an awful lot of logic in any of this.

Kind Regards, John