Log Cabin Supply Help

[GarryJ]

Hi all,

Just went to look at a job, the client has done and wired most of it however he wants the rest done by an electrician, he has an existing supply going from the consumer unit in the house to feed the 4 way board in his garage which is fine, RCD protected in the house and another in the 4 way garage board.

He has ran a 4 core s.w.a from the new log cabin to join the armour outside going to the garage and wants a switched fused spur at this joint on his garden wall, the spur is waterproof and he has appropriate outside glands, however he has installed another 4 way board in his log cabin with another RCD, would 3 RCDs on the same circuit cause problems?

Also he has ran an earth cable from an earth rod into the log cabin 4 way board, does he need this as we will already be picking up an earth from the existing armour? It is a small cabin with only 1 light and 2 sockets, will connecting the earth rod not be exporting a PME supply?

Thanks in advance for any help

 

[yellowvanman]

Whats the log cabin going to be used for, has it got a water supply and heating?

3 rcds on a circuit won't be a big problem but the upstream (in house) may trip before the garage or log cabin or trip as well as, so discrimination may not be optimum.

Earth rod is not exporting PME, if using this then you will probably need to terminate the SWA in a plastic box, and not take the earth (from the house) amy further.

 

[GarryJ]

The log cabin is just going to be used in the summer - has no water or gas supplys in the cabin, just 1 light and 2 radial socket circuits, yes I thought that and just earth the s.w.a going from the cabin to the plastic waterproof spur from the earth at the 4 way board in the cabin from the rod. Would 2 different earths (Rod and house earth) cause tripping problems with the RCD?

Thanks very much yellowvan man for your help

 

[yellowvanman]

SWA needs to be earthed at its source so earth swa to cabin at the fused spur.
2 different earths shouldn't cause a problem to rcds

 

[Deleted member 26818]

Is there any way of connecting the garage supply to a non-RCD way in the house board?
If not, then you might as well junk the other two RCDs in the garage and the log cabin.
Yes you will effectivly be exporting the PME, unless you keep the log cabin separate from the house earthing.

 

[GarryJ]

Ok thanks for your help

 

[Engineer54]

This sounds like a complete pigs ear of a job. Just stop now, and re-design the whole dammed layout!! This isn't rocket science to supply 2 buildings with power and lighting....

 

[Deleted member 9648]

We havent had an exporting PME ruck for ages.....must be time for another surely?....:wink_smile: