Garage conversion electrics

AndrewR · 27 May 2010

Hi,

I'm in the process of converting my garage and am at the point of insulating and the electrical first fix. The ceiling is to be insulated with PUR board within and below the rafters and the floor is to be a floating PUR and chip board affair.

As both the the floor and ceiling are to be fully insulated, then where can the the lighting and socket ring main cables run?

Having trawled through the similar subject posts I've concluded that the lighting cables should be ok within the insulated ceiling and that the socket ring main could run horizontally around the room, burried behind the dry lining, above the floating floor insulation (perhaps in conduit)?

Does this sound reasonable or is there a better solution?

Thanks,

Andy

LoveRocket · 27 May 2010

If you are using 1.5mm cable for the lighting circuit, and it is protected by no more than a 6 or 10amp OPD, then it will be fine, even if surrounded by insulation.

Are the walls insulated? If not then there shouldn't be a problem running cables in the dry-lining. Are you adding a new socket circuit for the conversion, or extending an original one? If it's a new one, why do you want to install a ring circuit (or 'ring main' as you called it)?

ban-all-sheds · 27 May 2010

AndrewR said:
I'm in the process of converting my garage

When you applied for Building Regulations approval, what did you say you would do to comply with P1?

Not trying to trip you up - if you (possibly unwittingly) said that the electrics would be done by a registered electrician then that's what you're now stuck with......

AndrewR · 27 May 2010

Thanks for the responses.

When I said it was a garage conversion I should have said it was a distinct and seperate utility, toilet and boiler room at the rear of the attached garage, which I've knocked into one. The construction is the same as the garage and I haven't applied for building regs as in my view I'm simply improving existing living space.

The walls are an un-insulated cavity, as per the rest of the house, and I intend leaving them so, just insulating the flat roof and concrete slab as well as I can. The room has and existing 1mm lighting circuit for the three original rooms and a 1.5mm supply to a socket. I had intended to utilize/extend these for one or two light fittings and further four sockets.

Sorry to show my ignorance but what's a 6 or 10 amp OCD? If its not protected by one can you suggest a way around it?

Thanks,

Andy

LoveRocket · 27 May 2010

I will deal with electrics, I'm sure Banal will deal with berating you over building regs etc.

OPD = Overload Protection Device, ie a fuse of circuit breaker. If it's 1mm, then it must be on a 5 or 6amp OPD, otherwise you will have to be very careful how you route the cable around the insulation.

1.5mm to a socket is unusual, 2.5mm is the norm. As it's 1.5mm it must either be fed from an FCU on another circuit, or directly from a 15/16amp OPD in the CU.

How far is the CU from the garage? Ideally you would run a new 20a radial circuit in 2.5mm for the new sockets you plan to install.

AndrewR · 27 May 2010

Thanks LoveRocket..........that just doesn't sound like something I should be saying......but there you go!

Having had a good look I made a mistake earlier and the socket cable is 2.5mm and unfortunately the lighting does seem to be 1mm.

Could I run the 1mm in conduit through the insulation (even if I had to use a larger size than normal)?

The CU is close enough to alter the cable but as I'm far from an expert I had hoped to avoid touching it.

Is an OPD installed within the CU or can it be located outside?

ban-all-sheds · 27 May 2010

LoveRocket said:
I'm sure Banal will deal with berating you over building regs etc.

I'm not going to berate him.

But because you are either hard of thinking or you are permanently looking for pathetic ways to criticise me you won't accept that.

LoveRocket · 27 May 2010

If your CU has MCBs then the lighting circuit will either be on a B6 or B10 MCB. If it's on a B6 then it can go through the insulation no problem.

You be much better adding a new radial circuit for your sockets rather than trying to extend an existing ring final. How many cables are behind the current socket? It sounds like that may be a spur.

AndrewR · 27 May 2010

The 1mm lighting cable is on B6 MCB, so if I understand you correctly this will be ok within the insulation.

Also I've got an existing cable running to an outside shed for lighting/power (RCD protected) that comes of a B16 MCB. This would also ideally run through the ceiling insulation aswell. Is likely to be ok though I'm unsure of its size.

The 2.5mm circuit currently supplies two sockets within the garage and the one within the room in question. This socket has one cable running into it (its on a B20 MCB).

ban-all-sheds · 27 May 2010

AndrewR said:
The construction is the same as the garage and I haven't applied for building regs as in my view I'm simply improving existing living space.

That may be your view, but I'm 99% certain that the work is notifiable, and requires approval. You should check with your council - ending up with part of your house being an unapproved conversion could bite you on the b*m in the future.

a 1.5mm supply to a socket

Is that on the ring, or is it a spur? If it's the latter is it a fused or an unfused one?

Sorry to show my ignorance but what's a 6 or 10 amp OCD? If its not protected by one can you suggest a way around it?

Is an OPD installed within the CU or can it be located outside?

TBH I think you should spend some time improving your competence before doing any electrical work.

LoveRocket · 27 May 2010

AndrewR said:
The 1mm lighting cable is on B6 MCB, so if I understand you correctly this will be ok within the insulation.

Also I've got an existing cable running to an outside shed for lighting/power (RCD protected) that comes of a B16 MCB. This would also ideally run through the ceiling insulation aswell. Is likely to be ok though I'm unsure of its size.

The 2.5mm circuit currently supplies two sockets within the garage and the one within the room in question. This socket has one cable running into it (its on a B20 MCB).

You really need to ascertain the size of the shed cable. Is it a T+E or SWA?

Are you saying that there's a B20 2.5mm circuit currently supplying three sockets in the garage area, and you want to extend from the last one to add more sockets? If so, then great, you can just add as many sockets as you wish, no need to mess around with stupid ring circuits or anything like that

AndrewR · 27 May 2010

Thanks for your advice guys.

Ban-all-sheds,

As the room was already part of the house and has been general living space is it was constructed in 1959, then why would I need building regs consent to improve it? That would be like saying you need consent to insulate your loft/floor anywhere else within the main body of the house.

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Garage conversion electrics

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