New sockets in garage

[autolycus]

Hi,

I have a detached double garage with an existing electrical supply. The consumer unit has two MCBs that are used for lighting circuits (internal and external) and two 32A MCBs. One is spare and the other is used for a ring main.

I now want to do two things: install two extra sockets in the garage itself and also install three sockets in the loft. My questions which I hope you guys can help with please are:

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?

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?

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?

4. As I would need to run two cables in each run of trunking/conduit what size would I need? I'm guessing 20mm if conduit or 25x16mm for trunking.

5. Is there any reason to use specific conduit back boxes like these https://www.tlc-direct.co.uk/Main_Index/Conduit_Pvc_Index/Boxes_Surface/index.html?
How are they better than what I'd normally buy - which is https://www.tlc-direct.co.uk/Products/MKK2142.html?

Thanks in advance for any guidance.

David.

 

[ban-all-sheds]

First question, are you aware that if you live in England or Wales you'll need Building Regulations approval for this? If so, do you plan to apply, and if so what do you plan to tell them will be the way you will ensure compliance?

 

[autolycus]

Yes, I am aware and it will be checked for compliance after the work is done - which is why I am asking the above question sin order ot ensure that ti does comply.

 

[AndyPRK]

You can spur a double socket off a ring, if this makes things easier.

 

[autolycus]

You can spur a double socket off a ring, if this makes things easier.

Yes, I know - but given that I want three new sockets in the loft that would mean doing a spur off three of the existing downstairs sockets, which seems a bit messy. And that still wouldn't give me the extra two sockets that I want to have downstairs....

 

[AndyPRK]

I thought your 2 new sockets downstairs could be Spurs if that made sense. Either off the ground floor or loft ring.

 

[autolycus]

Yes, having those two downstairs ones as spurs off existing downstairs ones would be an option. But the cable routing would be more complex that way compared to making them part of the new loft ring. Hence my question number 1 in the original post.

 

[Taylortwocities]

Yes, I am aware and it will be checked for compliance after the work is done -

Who will be doing the checking? If you are doing the work yourself, you have to raise a building notice with your local authority BEFORE any work is started. LABC will want to inspect the work at various stages and will expect that it is installed, tested and certified in accordance with BS7671.

Or did you expect that you would do the work, and then ask a registered electrician to notify it for you?

 

[autolycus]

My understanding is that as from 6 April 2014 a person who is registered with a third party certification scheme for electrical installations in dwellings will be able to check domestic electrical work that is undertaken by others and certify that it is compliant with the building regulations. And that's what will be happening in this case.

Anyway..... that aside, is anyone able to answer the original questions I asked please?

 

[JohnW2]

Yes, I know - but given that I want three new sockets in the loft that would mean doing a spur off three of the existing downstairs sockets, which seems a bit messy. And that still wouldn't give me the extra two sockets that I want to have downstairs....

Yes, having those two downstairs ones as spurs off existing downstairs ones would be an option. But the cable routing would be more complex that way compared to making them part of the new loft ring. Hence my question number 1 in the original post.

Even though it would probably be less convenient for you to implement, and not very electrically 'nice', from your point-of-view, the one advantage of installing all the new sockets ('downstairs' and loft) as spurs off the existing ring circuit (rather than creating a new, additional, circuit) is that it would then be non-notifiable work. The moment you connect anything to the currently unused 32A MCB (aka a 'new circuit') the work would become notifiable.

.. it's one of those arguably 'silly' situations in which the rules regarding notifiable work (with possible attendant hassle and cost) are such as to tempt people to undertake work in a manner which is (electrically) less satisfactory (or, at least, less nice') than it could/should be, even if it is still compliant with regulations!

Kind Regards, John

 

[autolycus]

Point taken, John. But in this particular case, the fact it is notifiable won't cause any extra hassle or expense. So that, plus the fact that if I did it with spurs I'd need two spurs off one of the existing sockets (which is obviously a no-no), means I'd rather go for the new ring.

And of course, even if I did go with spurs, I'd still appreciate answers to all of my original questions as they'd still be just as relevant.

 

[JohnW2]

My understanding is that as from 6 April 2014 a person who is registered with a third party certification scheme for electrical installations in dwellings will be able to check domestic electrical work that is undertaken by others and certify that it is compliant with the building regulations. And that's what will be happening in this case.

No it won't - at least, not legally - unless you already have this person on board. It was actually 6th April 2013, but your first problem will be in actually finding one of these people who are registered with a Third Party Certification Scheme. However, even if you find one, the rules require that such a person be engaged and involved before any work starts (and inspect as they deem necessary whilst the work proceeds) - which clearly is not what you are proposing

Kind Regards, John

 

[autolycus]

Apologies if the date is wrong. It was copied directly from the Department for Communities & Local Govt website.

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 have a detached double garage with an existing electrical supply. The consumer unit has two MCBs that are used for lighting circuits (internal and external) and two 32A MCBs. One is spare and the other is used for a ring main.

I now want to do two things: install two extra sockets in the garage itself and also install three sockets in the loft. My questions which I hope you guys can help with please are:

1. I'll be installing each new socket as a spur off an existing one. This will mean that a single ring main will have sockets both downstairs and upstairs (in the loft). Is that against the regs and/or a bad idea?

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?

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?

4. As I would need to run one 2.5mm T&E cable in each run of trunking/conduit what size would I need? I'm guessing 20mm if conduit or 25x16mm for trunking.

5. Is there any reason to use specific conduit back boxes like these https://www.tlc-direct.co.uk/Main_Index/Conduit_Pvc_Index/Boxes_Surface/index.html?
How are they better than what I'd normally buy - which is https://www.tlc-direct.co.uk/Products/MKK2142.html?

Thanks in advance for any guidance.

 

[JohnW2]

Point taken, John. But in this particular case, the fact it is notifiable won't cause any extra hassle or expense. So that, plus the fact that if I did it with spurs I'd need two spurs off one of the existing sockets (which is obviously a no-no), means I'd rather go for the new ring.

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..

And of course, even if I did go with spurs, I'd still appreciate answers to all of my original questions as they'd still be just as relevant.

Your question (1) has already been covered, at some length.
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.

Kind Regards, John

 

[JohnW2]

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