Sub main RCD protection

[jimmyjazz]

Hi All,
Think I know the answer but just looking for other options....I have been asked to install sub main 60 amp isolation switch supplying already installed 16mm T & E under floor to RCD protected consumer unit. Approx. 2 mtr of 16mm is in wall. I understand that regs require RCD protection for cable in wall, but I am trying to avoid loosing all circuits in event of trip. Would this also apply for meter tails from cut out passing through/up walls? Any ideas?

 

[ezzzekiel]

swa or surfice mount

 

[GaryM]

Yes it would.
I've got around a problem with meter tails once by having a 3mm metal plate fabricated to cover meter tails which were enclosed for a 1M run in a kitchen which used to be a garage.

 

[telectrix]

or you could protect the buried section with earthed metallic protection.

 

[GaryM]

BTW, I didnt 'earth' the metal plate which I had made as it wasn't an exposed conductive part nor extraneous.

 

[jimmyjazz]

Thanks for speed of replies, probably go for metal plate as cable is already installed.

 

[goldie]

Hi jimmy jazz
Regs state that rcd protection is for cables buried less than 50mm in the wall and use of unskilled persons. I would possibly install a 100mA rcd fo your main switch, so so your 30mA rcd protecting a bank of circiuts or 30 mA rcbo will trip first avoiding the whole board losing power in the event of a fault on 1 circuit.

 

[telectrix]

Hi jimmy jazz
Regs state that rcd protection is for cables buried less than 50mm in the wall and use of unskilled persons. I would possibly install a 100mA rcd fo your main switch, so so your 30mA rcd protecting a bank of circiuts or 30 mA rcbo will trip first avoiding the whole board losing power in the event of a fault on 1 circuit.

but the buried cable needs protecting by a 30mA RCD unless mechanically protected.

 

[jimmyjazz]

Thanks Goldie, but as this is domestic RCD has to be 30mA. I've used 100mA for TT main switch.

 

[peanutty]

whats the supply earth?

i must be going blind, missed TT main switch!!!!!!!

 

[goldie]

Yes..... quite right telectrix.

 

[peanutty]

have a word with dno about changing to PME. get hold of them using the emergency number on lecky bill(even not emergency just go through options) and their normally quite happy to come out, check and upgrade to PME at no charge usually even if head needs changing. might give you some better options for seperating circuits from one rcd, then with right mech protection in wall cable won't need rcd protection.