Proposed supply to shed.

[Guest22]

Ok, now before i get flamed this is proposed, i haven`t done this, i know its notifiable, etc etc. I am merely asking if this would be correct under the regulations which to my knowledge looking through them and into any de-rating factors, volt drop and any special consideration etc, And I can`t see anything that goes against them. Maybe that it could be considered bad practice is, the fact it spurs off from the spur but this is only to add RCD protection in the shed side of the circuit as to not let it trip in this house. Inside the shed it would be wired in 20mm PVC conduit or Flexible conduit, most information can be taken from the drawing i made. Note on the drawing, obviously the FCU within in the house isn`t existing. I wonder what you lot will say? Also, i understand i could put a garage CU on 4mm/6mm/10mm SWA with a new supply Coming from the exsisting CU, but i am not, and i`m not asking for other suggestions on how to feed the shed, merely if this is a within regulations to do so, thank you! Oh and
go easy, only an apprentice.
Its late so i bet this will have plenty of mistakes!

 

[Richard Burns]

Various scenarios presented below not all of which are consistent depending on changes made.

Best bet is to run the circuit as a dedicated circuit from the CU and not spur off the RFC.

Is the RFC in the house 30mA RCD protected, if it is then you will have 30mA RCDs in series and cannot tell which one will go first and so could still have the shed tripping out back at the house.
If the Ring is not RCD protected then you are changing a ring circuit but not providing the required RCD protection to general use sockets.

You have two 13A fuses in series and again cannot tell which one will go (although the MCB in the CU could still go first).
You could just have an RCD enclosure in the garage without the fuse (would be cheaper).

I assume the DP switch is for convenience in case of problems? However it may be better to have a DP switch back at the house in case of SWA problems (if the SFCU at the house is not double pole already) and the RCD FCU (or RCD) would also act as a double pole switch, so the DP switch is a bit redundant.

 

[Strima]

That's that answered then... Nice on Richard but how many pages will this one run on for? :lol:

 

[Deleted member 26818]

I'd go for the SFCU on the ring, an RCD socket in the shed, keep the SFCU for the lights.
If there's already an RCD at the CU, then there'd be no need for the RCD socket.

 

[Guest22]

Various scenarios presented below not all of which are consistent depending on changes made.

Best bet is to run the circuit as a dedicated circuit from the CU and not spur off the RFC.
Reason for spuring off the RFC is; the CU is located at the front of the and bearing in mind that this has solid concrete floors, all the sockets are supplied from long drop from the 1st floor, this would make this impracticable and at most insanely expensive i mean insanely, as it seems there is no simple route through the house)
Is the RFC in the house 30mA RCD protected, if it is then you will have 30mA RCDs in series and cannot tell which one will go first and so could still have the shed tripping out back at the house.
If the Ring is not RCD protected then you are changing a ring circuit but not providing the required RCD protection to general use sockets.
Yes, the board is NOT RCD protected, so i understand that i am changing the circuit, fair point.

You have two 13A fuses in series and again cannot tell which one will go (although the MCB in the CU could still go first).
You could just have an RCD enclosure in the garage without the fuse (would be cheaper).
Again i stated this was not ideal, i know, but the price for a RCD spur which can be bought for 11.99 compared to an standalone unit like you say, i have not seen them cheaper than that.

I assume the DP switch is for convenience in case of problems? However it may be better to have a DP switch back at the house in case of SWA problems (if the SFCU at the house is not double pole already) and the RCD FCU (or RCD) would also act as a double pole switch, so the DP switch is a bit redundant.
I have seen there were some guidance notes on supplies to outside sheds etc, and looking on the spuring from RFC option, when the supply got into the shed/garage it went a DP switch>13A Socket>3A Spur. But yes, I see what you mean, might be a good idea to maybe put the DP isolator in the house and or in the shed. Also I am simply trying to add protection by means of the RCD spur.

Spinlondon: (Don`t know how to put 2 quotes in one message) I'd go for the SFCU on the ring, an RCD socket in the shed, keep the SFCU for the lights.
If there's already an RCD at the CU, then there'd be no need for the RCD socket.
Yes, no RCD protection on the board at the moment. Would only use the RCD spur is it is infact cheaper than an RCD socket.

Thank you both for your help
​

 

[telectrix]

i am assuming that this is a terraced house and you can't run externally from the CU.

 

[Guest22]

i am assuming that this is a terraced house and you can't run externally from the CU.

Yeah, its a terraced house. No chance of running it externally.

 

[telectrix]

well, if i were doing the job, i'd go up from CU and under floorboards to back of house, then down externally with 6mm 3core SWA (buried or surface) to shed.

 

[Deleted member 26818]

Yes, no RCD protection on the board at the moment. Would only use the RCD spur is it is infact cheaper than an RCD socket.

Problem with this, is that you will have two 13A fuses in the same line.

 

[telectrix]

he can wrap some silver paper out of a smoke packet round the upstream fuse. benson and hedges discrimination.

 

[Guest22]

Id rather go heavy duty and jam a nail in there!