Advice on tails, earthing and 60amp switched isolator

Sbc · Oct 3, 2012

Hi All, first time on the forum and looking forward to learning loads of good stuff from the experienced sparkies.

I recently gained 2382 & 2392 qualifications and am now trying to get experience in the real world.

I have rewired my outbuilding fitting a metal clad garage consumer unit 63a 30ma rcd main switch, 1x32a ring + 1x6a lights and supplied by the existing 6mm 2 core SWA over a 25 meter run.

The supply is TN-S with 1361 type 2 fuse (rating not verified) theres 25mm tails from cutout to meter and 16mm tails from meter to a dodgy 60amp rewirable ceramic isolator which im going to replace.

The house is fed by 16mm tails (7m run to CU) from the ceramic isolator as is the 6mm to outbuilding
The earthing and bonding is 10mm.

One thing i don't like is the 10mm earth goes from the MET to the gas then to the CU and im guessing on to the water... is this permissable?
Do the tails and earthing sound adequate or should i consider upgrading (which would be a real pain)

I also didnt like the 6mm swa and the 16mm tails paired and terminated together in the same terminals or is this common practice... is there a better way?

Also, I understand 60A protection for 16mm tails are OK but surely is useless for the 6mm swa as the swa rating would be around the 47A mark... y/n ?

Im sure theres more questions somewhere.

Would be gratefull for any thoughts, guidence and advice

Thanks Sbc

Gritishbasspark · Oct 3, 2012

Firstly welcome
I would recommend changing the isolator for a new switch fuse, the outbuilding sub main I would either put in a high integrity consumer unit and put the sub main in a rcbo 32A or separate board if u don't want to change this would stop nuisance tripping if you had problems in the outbuilding. Main earth I would upgrade to 16mm to the MET then 16mm from that to the consumer unit and 10mm's to the bonding. Linking earth cable from MET to the gas then to the consumer unit is not right separate one to the consumer unit, it is ok to link the two bonds together but the cable must not be cut I would normally run in two unless it was a real pain. Hope this helps

David

Deleted member 26818 · Oct 4, 2012

As the existing switch fuse is 60A, the 16mm² tails are fine.
You say that the 10mm² earth goes from the MET to the gas and then the water?
Yes it is permissable to run the earth as you describe.
There's no requirement for the conductor to be continuous, that's just something some Local Authorities started some time ago, as their Building Control Officers didn't quite understand the Regulations at that time.
10mm² is most likely oversized and definately doesn't require being replaced with a larger size.
Terminating the 16mm² and 6mm² conductors in the same terminals is not ideal, but it is fairly common.
What would be better would be to source a switch fuse with two sets of terminals, or if not available, split the supplies after the switch fuse by means of Henly Blocks.
You could if there is enough slack, terminate the SWA in the CU, but there is no need for it to be RCD protected.
I don't know what type of CU you have, it may not have a non RCD protected way available.