Garage Supply - 2 way metal consumer unit in a seperate garage

[Dunc88]

Seems to me,like you stated, just fit main switch cons unit in the garage off a Rcd protected Mcb and be done with it

Yeah, that will do the trick! Thanks all

 

[Nimmasaurus]

time delayed rcd in the house protecting the garage circuit, that way the rcd in the garage consumer unit will trip first.

 

[Midwest]

Somewhat complicated solution, for an event unlikely to happen?

 

[Octopus]

time delayed rcd in the house protecting the garage circuit, that way the rcd in the garage consumer unit will trip first.

The op has already said the cu is a dual RCD unit with no spare ways - how is adding a time delay going to improve the situation? And why do people think by TTing a shed or garage would prevent the house cu RCD tripping?

 

[Nimmasaurus]

Replace one rcd with the delay one? OP wants to avoid the garage potentially tripping an rcd in the house, so if there's a short in the garage the garage cons unit should trip before the house one if it's a timer delay one. On a 5m run it's not that big a deal to have to flick a switch in the house c.u. We recently did a farm shed that was about 120m from the main supply and that's what we did - time delayed rcd in house c.u. and normal rcd in the shed. 16mm cable to run the power to the shed because of the length of run with voltage drop.

 

[Anthony_wayne]

Shame it's not a high integrity dual rcd board, I just installed a similar set-up, but used an mcb to protect the 4mm swa for the garage which had a 63A RCD main switch with 2 mcbs in the unit.
Never been a fan of large consumer units with no none RCD ways.

 

[Toneyz]

Replace one rcd with the delay one? OP wants to avoid the garage potentially tripping an rcd in the house, so if there's a short in the garage the garage cons unit should trip before the house one if it's a timer delay one. On a 5m run it's not that big a deal to have to flick a switch in the house c.u. We recently did a farm shed that was about 120m from the main supply and that's what we did - time delayed rcd in house c.u. and normal rcd in the shed. 16mm cable to run the power to the shed because of the length of run with voltage drop.

Because it would make the other existing circuits non compliant

 

[Dave OCD]

I ordered a time delay RCD last week but it was delivered the same day !

 

[Had8Lives]

The only thing that's not been mentioned and I'm sure someone will correct me, I was told by an ELECSA assesor that you're not allowed to export a TNCS earth in less than 10mm cable. So, as you can't get an mcb unprotected in the house consumer unit, have a main switch in your garage consumer unit and put an earth rod in to earth your garage consumer unit.

 

[Octopus]

I'd rather export a decent earth than rely on a twig ....

Tin hat on..

 

[Had8Lives]

I'd rather export a decent earth than rely on a twig ....

Tin hat on..

Ah, but, if you happened to be touching a metal clad socket and lightning struck a power line and it burned your arm you'd wish you'd put a twig in lol

 

[Midwest]

The only thing that's not been mentioned and I'm sure someone will correct me, I was told by an ELECSA assesor that you're not allowed to export a TNCS earth in less than 10mm cable. So, as you can't get an mcb unprotected in the house consumer unit, have a main switch in your garage consumer unit and put an earth rod in to earth your garage consumer unit.

Here goes then; in a typical domestic property, the 10mm bit only relates to the minimum size cable if you have extraneous conductive parts to bond. Or run a separate 10mm protective bonding conductor to the extraneous conductive part in the garage, and run an appropriate sized swa for load/vd only. Or as you suggested turn supply into TT, bonding locally as necessary.

Don't think there is an extraneous conductive part in the situation described by the OP.