Power cable to garage/workshop

[Jmac80]

Hello all
My garage is badly needing the electrics sorted on it.
The garage is built onto the side of the house and was added about 20 years ago along with a rear extension to the kitchen.
A new hagner consumer unit was fitted in the house about 5 years ago, it has a row of normal mcbs for lights etc and then another row that is protected by rcd for sockets etc.

Currently there is a 2.5mm cable with a 32a mcb on rcd side feeding the sockets to the garage and extension. there is two live wires coming out the top of the mcb suggesting a ring however the sockets in the garage come to a dead end after 5 double sockets, maybe it's 1 radial to the extension sockets and another radial to the garage sockets? would that mean 32a poses a fire risk?

The lights for the garage and extension is a 1.5mm cable coming from 6a mcb, there is just one live cable going into the mcb.

What i would like is a separate small consumer unit in the garage doing the lights and sockets, however i would like to allow for some future 16 sockets, maybe a nice new planer/thicknesser and air compressor

The new cable feeding the garage cu would need to go under the floorboards (joisted floor construction and non insulated) for about 8 metres to get to the garage, probably about 11 / 12m in total.
I'd like to do most of the labouring work myself to save some money so my questions are what size cable would be recommended to feed the garage cu ? And would you advise armoured?

Thanks

 

[mindthatwhatouch]

Sounds like you have 2 existing radials, Is it possible to join these together to form a ring? then un a separate supply to the garage for the 16 Amp
If not,
Minimum I would suggest is 6mm Armoured or 10mm T&E
Small consumer unit in garage with MCB for Ring circuit and MCB for 16amp socket.
Depends how far you want to future proof it, what sort of load you will realistically be running?

 

[Willy]

Do you have the certificate from when the consumer unit was installed? It should answer the question of whether or not you have a radial in the garage.

If it is a radial and supplied with 2.5mm cable, it should have no larger than a 20A MCB protecting it. A 32A MCB on 2.5mm cable supplying a radial, is as far as I know not legal and poses a fire risk.

Is it possible that you actually have a ring which supplies both the garage and the extension, but that the last socket in the garage is a spur off that ring?

In any case, the size of the new supply to your garage really depends on how many appliances you want to run simultaneously. It sounds like you would end up with a new ring in the garage (32A), a radial for one or two 16A sockets and perhaps a dedicated 6A circuit for the lights? That might suggest a 6mm or 10mm T&E cable supplying it. As for armoured, unless it's going underground, I don't believe it's necessary.

I just had my whole house rewired. I specified 10mm cable for my garage. The sparky was convinced I only needed 6mm for the same type of application you have suggested (though without the need for 16A outlets).

 

[HOJ]

My advice: is to call in a "Part P" Registered Electrician, to provide a "Design and Verification" schedule, using the 17th edition of the IEE Wiring Regulations.

You can then install the specified cables and fittings, to first fix stage, they will then connect and commission, and be responsible for signing off the completed work, as this is "Notifiable work" under Building Regulations.

 

[Hickorystick]

Last month I had the electrics to my garage workshop completed.
The sparks used a spare way on my house consumer unit - fitted a 40amp breaker and ran a large T&E cable across to the garage.
A small 4 way consumer unit was fitted and a 16amp commando socket was wired up for my bandsaw.
I ran the circuits for the 5x lights and 6x 13amp sockets myself which the sparky checked then he did the terminations into the consumer unit. I was then issued with the required electrical certificate. He charged me £300 for supply and fit.

Phil

 

[woodfarmer]

2-3 years ago I had to upgrade the electrics to the barn to run a 5.5 HP motor for my log splitter.
So if I were you I would run a 10mm supply cable from the house consumer box to a new consumer box in your workshop. The reason for the 10mm over 6mm is if you have one motor running then choose to start another the staring current may well cause more voltage drop than desirable. especially for things that start against a load (eg automatic air compressor). I would also use armoured cable simply because it is rodent and nail proof.

My own run here was 50 metres of this http://www.tlc-direct.co.uk/Products/SW10slash3.html and the upgrade made a world of difference over the old supply even for simple things like my table saw now starts quicker. Oh and for some reason my welder is much better now, smoother and just easier to use. The cable will carry 53 amps continuously, but the big thing is there is very little volts drop even so the lights do dip for a second when I start the log splitter.

PS make sure you order a pair of glands when you order the cable.

 

[Jmac80]

Minimum I would suggest is 6mm Armoured or 10mm T&E
Small consumer unit in garage with MCB for Ring circuit and MCB for 16amp socket.
Depends how far you want to future proof it, what sort of load you will realistically be running?

Well i would like a decent planer / thicknesser, 3kw, But i have a freezer out there a PC and plenty other electrical tools & dust extractor.

As for armoured, unless it's going underground, I don't believe it's necessary.

I was wondering that as it's basically just under my house going to an attached garage. There is plenty of other older wiring under there and it is not armoured.

Last month I had the electrics to my garage workshop completed.
The sparks used a spare way on my house consumer unit - fitted a 40amp breaker and ran a large T&E cable across to the garage.
A small 4 way consumer unit was fitted and a 16amp commando socket was wired up for my bandsaw.
I ran the circuits for the 5x lights and 6x 13amp sockets myself which the sparky checked then he did the terminations into the consumer unit. I was then issued with the required electrical certificate. He charged me £300 for supply and fit.

Phil

Something like this one phil? http://www.screwfix.com/p/mk-sentry-4-w ... unit/33248

2-3 years ago I had to upgrade the electrics to the barn to run a 5.5 HP motor for my log splitter.
So if I were you I would run a 10mm supply cable from the house consumer box to a new consumer box in your workshop. The reason for the 10mm over 6mm is if you have one motor running then choose to start another the staring current may well cause more voltage drop than desirable. especially for things that start against a load (eg automatic air compressor). I would also use armoured cable simply because it is rodent and nail proof.

My own run here was 50 metres of this http://www.tlc-direct.co.uk/Products/SW10slash3.html and the upgrade made a world of difference over the old supply even for simple things like my table saw now starts quicker. Oh and for some reason my welder is much better now, smoother and just easier to use. The cable will carry 53 amps continuously, but the big thing is there is very little volts drop even so the lights do dip for a second when I start the log splitter.

PS make sure you order a pair of glands when you order the cable.

Hi, Does it have to be SWA? as garage is attached to house?

Thanks all

 

[mindthatwhatouch]

No it doesn't have to be SWA,
but you get a higher current carrying capacity with SWA, and you can get away with not protecting it, i.e clipping it direct within the garage. Personally would not want un protected T&E on a garage/workshop wall though i don't know if this is a factor.
Get a couple of electricians round for quotes, tell them what you want and ask for suggestions.
May be able to find someone who is happy for you to do the bulk of the work as suggested earlier.

 

[Jmac80]

Shall do, Will track one down on Monday and see what he say's.

 

[Jmac80]

I guess the price difference is not huge so i could just go SWA

 

[woodfarmer]

I guess the price difference is not huge so i could just go SWA

I have often found that doing the job well the first time often saves money..

Put another way, if cost is always the main concern why doesn't everyone run trabants on remoulds

No need at all for merc, fords et al.

 

[Hickorystick]

Not exactly the same consumer unit but the Screwfix one has identical capacity...

 

[Phil Pascoe]

Don't ever make the mistake of thinking Screwfix is automatically the cheapest - I've just looked up something that is £18.99 in Screwfix and £9.36 somewhere else. They have bargains - but caveat emptor.