Power to a garage

[Skipsmark]

Hi, I'm looking for some advice please, will be engaging electrician to carry out work but would like to be reasonably well informed before having the conversations. I would like to do as much of the work that I can safely accomplish as possible but acknowledge that the design and testing elements are going to be professional jobs as a minimum.

The garage already has power to ceiling lights and a couple of sockets supplied via T&E run from the house to the garage (about 800mm) via plastic conduit just above head height, (I know - not my work). There's no RCD or MCB in the garage at the moment. There are no water or gas pipes to worry about.

In future I want to use the garage for some hobby and craft type work so will want to run some power tools, desk lamps, and laptop. I may install a small TV at some point. There is also a tumble dryer which is used maybe twice a week in the wet/cold weather (so about 50 weeks per annum then).

The garage is about 3 x 7 m in size and I'm thinking of putting in about half a dozen sockets around the walls for convenience sake. The sockets will be wall mounted (about 750mm high) and connected by plastic conduit securely fixed to the walls.

Would a radial circuit using 2.5mm T&E be sufficient/appropriate for this kind of expected use?

If that is the case then would a garage CU with RCD protection and MCBs of 20 AMP for sockets and 6 AMP for the lights be a good match?

Actually getting supply to the garage itself looks a bit of a challenge, digging down between the house and the garage (a narrow and short passage that is bridged by a timber gate) is not my preferred choice given proximity of drain, foundations etc. Going overhead (above 3.2 m will look very odd and ugly). Any ideas/experience of how this can be/has been done please?

Leaving that aside for the moment, I have spare capacity on the house CU (which is mounted on an external facing wall) and would like to know if adding a 32 AMP MCB and then running 4mm SWA along the outside of the house to the garage would be about right? If so, can the cable be clipped to the wall directly or would conduit be required?

Apologies for the long read, any advice very gratefully received. Thanks

 

[winston1]

You don't need a CU, RCD, or MCBs in the garage. All that is already in the house. Your feed to the garage can directly run a ring final in there with a 4mm2 SWA feed off a 32A MCB, or radials if using a 20 A MCB. Lights can be run via a switched FCU with a 5amp fuse.

 

[bernardgreen]

You don't need a CU, RCD, or MCBs in the garage.

It is sensible to have the earth leakage protection provided by a dedicated RCD that protects ONLY the garage. This could be in the house but NOT the RCD(s) that protect the house or better, an RCD in the garage.

Reason is that an earth leakage in the garage should not trip the RCD for the house and leave the house without power / lights. With the RCD in the garage then the person in the garage does not have to go to the house to reset the RCD

 

[ban-all-sheds]

would like to do as much of the work that I can safely accomplish as possible but acknowledge that the design and testing elements are going to be professional jobs as a minimum.

You must speak to your electrician about this - only she can decide how much she is happy for you to do.

The sockets will be wall mounted (about 750mm high) and connected by plastic conduit securely fixed to the walls.

Use steel conduit - it is so much nicer.

Would a radial circuit using 2.5mm T&E be sufficient/appropriate for this kind of expected use?

Ask your electrician - she is the one who will have to sign a certificate to say that she did the work.

Actually getting supply to the garage itself looks a bit of a challenge, digging down between the house and the garage (a narrow and short passage that is bridged by a timber gate) is not my preferred choice given proximity of drain, foundations etc. Going overhead (above 3.2 m will look very odd and ugly). Any ideas/experience of how this can be/has been done please?

Ask your electrician - you are paying her for her expertise, including that in this area.

Leaving that aside for the moment, I have spare capacity on the house CU (which is mounted on an external facing wall) and would like to know if adding a 32 AMP MCB and then running 4mm SWA along the outside of the house to the garage would be about right? If so, can the cable be clipped to the wall directly or would conduit be required?

Ask your electrician - she is the one who will have to sign a certificate to say that she did the work.

 

[flyingsparks]

Use steel conduit - it is so much nicer.

And completely unnecessary for a job like this, not to mention the additional costs involved with labour and initially buying it.
I agree in a commercial workshop - yes..

OP - plastic conduit would be fine.

 

[Skipsmark]

Many thanks for taking the time to reply everyone, it's much appreciated. It hadn't occurred to me to just rely on the house supply Winston so thanks for pointing that out, I think I prefer to follow Bernard's suggestion and keep things separate though. I did wonder about the steel conduit though Ban All Sheds, is it "much nicer" on aesthetic grounds or are there other factors to consider here in terms of risk and cost? Unless there's a compelling reason I think I'll take Flying sparks advice and stick to the plastic option. I do also wonder a little about the need for the electrician to sign a certificate to say they did the work, shouldn't it be the case to sign to say that the work passed the appropriate tests and meets certain standards? Thinking about Air Safety for instance we don't expect the test pilot to have actually riveted the wings.

 

[ban-all-sheds]

And completely unnecessary for a job like this

I didn't say necessary.

I said nicer.

 

[ban-all-sheds]

I did wonder about the steel conduit though Ban All Sheds, is it "much nicer" on aesthetic grounds or are there other factors to consider here in terms of risk and cost?

There are probably no risks associated with using plastic. Steel will cost more. I just think it is better.

I do also wonder a little about the need for the electrician to sign a certificate to say they did the work, shouldn't it be the case to sign to say that the work passed the appropriate tests and meets certain standards? Thinking about Air Safety for instance we don't expect the test pilot to have actually riveted the wings.

Well we would expect him to have actually done that if he signed a certificate to say that he had.