new garage wiring

[george765]

My newly built garage is an extension to the side of the house. Is there any reason/requirment to have an additional CU in the garage ?
Can I just take a new ring and new lighting circuit from the house CU ?

 

[wingcoax]

No specific requirement,but normally there would be a "garage unit" fitted with a 32A and a 6A cb. This would be fed from the main CU. At the main CU i hope you have an RCD fitted. If not get a qulified sparks in to do the job. This is also a notifiable job, meaning the local council want their pound of flesh.

 

[Lectrician]

There is no 'normally' about it.

'Garage' CU's are cheap tat.

Nothing wrong with extending your current circuits into the garage, or installing new circuits from the current consumer unit.

 

[Steve]

I fitted a 40A submain in 6mm² SWA from the house.

The submain itself is not RCD protected. The lighting in the shed needn't be RCD protected either - all wiring is exposed so ecapes the new RCD provision of the 17th. Thus I have a very robust supply to the lighting at the shed. The only RCD provision is that to the sockets, which is done via a 32A RCBO.

 

[Taylortwocities]

There is no 'normally' about it.

'Garage' CU's are cheap tat.

Nothing wrong with extending your current circuits into the garage, or installing new circuits from the current consumer unit.

In addition, if you extend the existing circuits you do not need to notify the works as there are no new circuits and your garage is integrated with the house - that means it is not electrical work outdoors.

Per the above, the additional sockets will need RCD protection. Not needed on the lighting if all wiring is surface/conduit.

 

[george765]

I quite like the idea of a small CU in the Garage (a good quality one) Can I suppy this garage CU, from a 50A MCB on the House CU (I have a space) ? rather than use a henly block and a switchfuse. If so what size cable should I use from the House CU to the garage CU ?

 

[bongos]

I quite like the idea of a small CU in the Garage (a good quality one) Can I suppy this garage CU, from a 50A MCB on the House CU (I have a space) ? rather than use a henly block and a switchfuse. If so what size cable should I use from the House CU to the garage CU ?

If you want to use a 50A MCB then you'll have to use 10mm² cable...

The proper way to design this circuit is to work out your design load and then select your cable and protective device for protecting the cable. Just because you have a spare 50A MCB there is nothing to stop you buying a new one of a more appropriate rating for a few pounds.

Or do you want a 50A submain in the garage?

If you're installing a new circuit form the CU then this work will be notifiable to your LABC.

 

[skenk]

If you need a 50A supply to the garage you will need to watch your maximum demand doesn't rocket past your supply capacity.

 

[george765]

Or do you want a 50A submain in the garage?

Isn't a 50A supppy from the house CU to another CU in the garage as I described called a submain ?

I figured 50a for the garage based on a
32A MCB for ring (about six sockets) 6A MCB for the lighting, 16A MCB radial for the Electric door and 6A MCB for garden lighting.

max load I suspect at any one time 20A power+8A door+2A lighting+2Am/lighting
perhaps a 40A supply would be enough ?

 

[RF Lighting]

What sort of stuff will you be running in the garage? I'm assuming just a few general power tools?

I have a 50A supply to my garage on 16.0mm² SWA, but I have a big(ish) welder, and quite a well equipped workshop running off that supply, oh and a supply to the shed, and a couple of freezers, and 6kW of heating, and a 32A CEEform test socket.

For normal usage I'd have said 40A would be more than adequate.