• Welcome to the new forum. We're now hosted on ElectriciansForums.net rather than ElectriciansForums.co.uk - Chat about the forum upgrade by CLICKING HERE

Welcome to our Electrical Forum - We started out providing electrical advice just for the UK - But now we have specific advice for the USA too! - Register for free and share American Electrical Advice.

Discuss New circuit to detached shed/garage in garden. in the Electrical Wiring, Theories and Regulations area at ElectriciansForums.net

David999

EF Member
Hello I am new to this forum and need a little help from an experienced spark to help me design a circuit to wire a detached garage (two sockets and ceiling lights) from a house ring main to 18th edition standards. This will be notifiable so everything has to be pukka. Cable can be in steel trunking or armored but prefer steel trunking option. I do know the basics but as this is my first outbuilding wiring I would really appreciate some pointers. My idea is to replace a socket in the house to a switched 13 A FCU drill through wall to outside and use steel trunking buried under garden slabs to garage wall. Drill through garage wall and connect cable to an RCD (thinking that a mini CU is overkill) as the house CU doesn't have RCD protection. At this point not sure of best option to split garage supply to sockets and 3 amp protected lighting..... Thanks for your help.
 

buzzlightyear

please let me back in to the prison cell.
Electrician's Arms
welcome ,before we start are thier any water services to the det
garage ?and what are the services from DNO.
 

AlmondSauce

Regular EF Member
While you can go off a FCU for this, bear in mind you're obviously limited to 13A for everything, which could be an issue for a garage. I wouldn't bat an eyelid if it was (for example) a tiny shed that might have a single socket for someone to plug a lawnmower in every so often, but a detached garage is a different kettle of fish. If someone decides to plug an electric heater into one socket while using a power tool in another, that could easily take you over the limit.

Much better IMHO would be to go back to the consumer unit, and come off a dedicated RCBO.
 

Murdoch

Electrician's Arms

Spoon

Forum Mentor
What's wrong with that suggestion Murdoch?
I think he may be getting at, if the OP is going to use a CU in the garage then that will have a RCD on it. The armour cable doesn't need it. This avoids discrimination in RCD's.
I could be wrong though.. :)
 

Pete999

Forum Mentor
I think he may be getting at, if the OP is going to use a CU in the garage then that will have a RCD on it. The armour cable doesn't need it. This avoids discrimination in RCD's.
I could be wrong though.. :)
Oh OK thanks for that
 

David999

EF Member
Thank you for your input. As I suspected not a straight forward job. Yes it is a garage that will be used as a relaxation room with a fridge freezer and in the winter their may well be a heater. However my main concern would be voltage drop with the 10m run from house to garage. The good news is that there is very little demand on the ring so if there is a 13 amp fcu to garage and 3 amp to lighting and these connected to an RCD I think it would work. My confusion is the best way to achieve a tidy job without a mini CU in the garage. And what is in line with 18th edition guidelines. There won't be an issue with RCD discrimination because the house does not have one on the main CU. Thanks
 

Spoon

Forum Mentor
Yes it is a garage that will be used as a relaxation room with a fridge freezer and in the winter their may well be a heater.
Are you sure 13A will be enough for the 'relaxation room'?.
A 2 KW heater & fridge freezer may be near that, or over.
May be better to wire back to CU so they have more options on what to use in the garage.
 
  • Like
Reactions: DPG

David999

EF Member
Yes I agree and to make future proof. I guess you are right but its more complicated to achieve and not sure the customer will be keen. It would be good if I could present him with both options and pricing so he can decide. Hence also need to know the best way to arrange the wiring in garage if taken from Ring. Thanks for your input. This job is happening on Monday weather permitting :)
 

Spoon

Forum Mentor
If you are going to tap of the existing ring then I would quote for LED lights. Give them more to play with on the socket front.
 

Electrician Talk

Electrical 2 Go - Electrical Supplier and Electrical Wholesalers
Electrical Insurance
ElectriciansForums.net (formerly known as ElectriciansForums.co.uk) was setup in April 2006 to provide free electrical advice to both professional and DIY electricians. Whether seeking advice for auto electrics, trying to find electrical installation condition reports (EICR) form downloads, or whether you're here just to talk to other electricians; we've been a first-choice website for tens of thousands of sparkies for well over a decade.
Top