Garage supply and earthing

[Rockomuir]

I have been ask to look at supply a shed/summer house with a supply for a s/outlet and a light. Due to the small load I was going to spur from a socket, swa to shed then a little 2 way cu. this is because the run from the d/b is complicated and involves a lot of remedial work that the customer does not want. My query is what about earthing for the shed. The house is on a tt system, do I have to provide a earth spike or can I export from the met. I am a little worried about my ze reading not being low enough. Also I am a little bit concerns about no discrimination between the shed and house d/b

Many thanks

 

[telectrix]

if you are going to spur from a socket with a 13A FCU, no protection is needed in the shed ( except to fuse down to 5A fot lighting) assuming the circuit you are coming off id RCD protected. you can add another earth rod at the shed, no problem.

 

[GLENNSPARK]

as Tel....RCDfcu to feed the shed....

 

[Rockomuir]

Thanks for the reply,

It is RCD protected as it has RCD as main switc. With an fcu to feed the shed then I will do away with the 2 way board and just fuse down the lights. Would you recommend an earth rod? I have heard different theory's and the regs do not clear it up for me

 

[telectrix]

i would fit an additional rod. it may even reduce the Ze of the whole installation. can't do any harm anyway. your problem is going to be that a fault in the shed would trip out the whole house. the ideal way would be to replace the CU with a hi-integrity board and feed the shed from a non-RCD circuit, then RCD in shed, but, as you say, it's a problem feeding from CU, so the FCU option is the easiest and cheapest. just make sure you use a double pole FCU so that you can easily isolate both L and N to the shed in case of a FAULT.

 

[GLENNSPARK]

i would fit an additional rod. it may even reduce the Ze of the whole installation. can't do any harm anyway. your problem is going to be that a fault in the shed would trip out the whole house. the ideal way would be to replace the CU with a hi-integrity board and feed the shed from a non-RCD circuit, then RCD in shed, but, as you say, it's a problem feeding from CU, so the FCU option is the easiest and cheapest. just make sure you use a double pole FCU so that you can easily isolate both L and N to the shed in case of a FAULT.

not RCD the feed to the shed?...on a TT Tel?...high integrity board with an s type in there....then 30mA in the shed.....

 

[SparkyDips]

double pole switch in shed/summerhouse, to socket, to SFCU for light.

 

[Rockomuir]

Thanks all for the reply very helpful

 

[telectrix]

not RCD the feed to the shed?...on a TT Tel?...high integrity board with an s type in there....then 30mA in the shed.....

oops, forgot about the TT there.

 

[Engineer54]

Thanks for the reply,

It is RCD protected as it has RCD as main switc. With an fcu to feed the shed then I will do away with the 2 way board and just fuse down the lights. Would you recommend an earth rod? I have heard different theory's and the regs do not clear it up for me

On a TT system, it is always better to have more rods!! But if your going to install an earth rod use at least 2 X 1.2m 5/8'' rods coupled together to give you a decent depth and there-by rod stability. Linked together either directly or via EMT or the steel wire armour of your supply cable...