RCD or Main switch in garage board

[Ian1972]

Hi this may be a simple answer to my question but I can't find the answer in the regs

If im fitting a garage board from a consumer unit with RCD protection do I need to have RCD protection in the garage board?

I'm guessing I don't need an RCD at the garage board but I can't find a definite answer in the regs

Thanks in advance

 

[buzzlightyear]

If im fitting a garage board from a consumer unit with RCD protection do I need to have RCD protection in the garage board?

The rcd in the consumer will be OK.
Feeding the garage .

 

[cireland]

Fitting a second RCD gives rise to selectivity issues.

 

[Ian1972]

Cheers guys what I thought

 

[davesparks]

If im fitting a garage board from a consumer unit with RCD protection do I need to have RCD protection in the garage board?

Maybe, maybe not. What type and rating of RCD is fitted at the supply end and what type and rating of RCD is required in the garage?

 

[littlespark]

It depends on the wiring type between the house and the garage.
Ie, twin and earth buried in wall less than 50mm, then it needs an rcd to protect it.
SWA, you could have an mcb at the house, and rcd in the garage.

Even then, the garage could be an rcd mainswitch with individual circuit mcbs or a regular mainswitch and rcbo’s.

 

[timhoward]

As already alluded to, more info is needed to answer.
For all we know it could be an 100ma main switch RCD for a TT setup in the house.

 

[Ian1972]

As already alluded to, more info is needed to answer.
For all we know it could be an 100ma main switch RCD for a TT setup in the house.

It's a 30ma type F RCCB in the house board 40A MCB with 10mm cable to Garage board not actually fitted in the garage but in a kitchen cupboard to feed an ASHP, control panel and a heat recovery unit

 

[timhoward]

I'm guessing I don't need an RCD at the garage board but I can't find a definite answer in the regs

In general terms, the relevant regs would be in the following areas:
1) loads requiring an RCD
2) Whether the prospective fault current will operate the upstream breaker because the Zs is low enough, or whether an RCD is needed for fault protection
3) Whether RCD protection is required due to the way the cable is run (Impact Protection)

t's a 30ma type F RCCB in the house board 40A MCB with 10mm cable to Garage board not actually fitted in the garage but in a kitchen cupboard to feed an ASHP, control panel and a heat recovery unit

I'm fairly sure this would be adequate in practise (interesting it's a type F).

The only (subjective) question in my mind is whether there's any possible better design so you aren't adding even more loads to a common RCD.

If the distribution circuit doesn't require an RCD for impact protection or fault protection (e.g. it's SWA or is not buried in walls at all and it's not a TT supply) then I'd probably be looking at supplying it from a non-RCD protected MCB or split tails and fuse, and have the RCD protection on the final circuits in the garage board (RCBOs).

(just noticed @littlespark said most of this too)