rcd

[ezekiel]

can anyone explain if:

a tt installation must be protected by 100ma rcd as main switch?

or

if all circuits have 30ma protection is this enough?

 

[Spark123]

It depends on a few things - if the consumer unit is metal clad then it should have upstream protection or additional protection against the meter tails becoming damaged.
Apart from that then I don't see why there is a need to supply a 30mA device from a 100mA device, you'd need to pay attention to the requirements for isolation on TT systems (all lives).

 

[hairyben]

All circuits need RCD protection. If they all have 30mA, eg RCBO's, then no need for an 100mA RCD mainswitch, unless there's a submain between meter head and DB.

 

[securespark]

Notwithstanding the advice from 123 about a metallic enclosure.

Either you need to fit special protection to prevent the tails shorting on the enclosure, or fit RCD protection to the tails.

 

[ricicle]

If this is a new domestic install then there is a fair chance ALL circuits will need 30mA protection due to the buried cables reg.
This will allieve the need for 100mA protection. Bear in mind the continuation of supply if an RCD operates (dual RCD board) and the comments above about m/c boards.