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mjf

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Fitting a garage consumer unit in a detached garage / workshop. The consumer unit in the house is a dual 30ma rcd consumer unit. An swa will feed from the house to the garage. My question is around RCD's, should the 30ma rcd at the house be used and just a 2 pole main switch at the garage, or use a 100ma at the house with a 30ma at the garage ?
 
as long as the SWA does not require RCD protection, fit RCD at garage. saves your legs going to house to reset.
 
Tricky one that especially as more info needed. So what is it to be? TT at garage or export TN-C-S. How far is it. So you would want to protect the outer sheath of the SWA in case someone chops it. So rcd for that. But if TT at garage then you don't want the armour to form an earth at the TT end. To achieve selectivity you would need s type rcd on supply end. Then normal RCD at garage end. As I say more info to be more definite.
 
The house is TNCS, and the cable run to the garage approx 25m. Yes water at the garage. As the swa is not feeding any sockets or lights direct but is via a garage consumer unit I don't see why it requires a 30ma rcd at the house. If someone were to get a shock in the garage it would trip the rcd in the house and could be reset by someone in the house unaware why it's triped. Hence the 30ma rcd at the garage.
 
The house is TNCS, and the cable run to the garage approx 25m. Yes water at the garage. As the swa is not feeding any sockets or lights direct but is via a garage consumer unit I don't see why it requires a 30ma rcd at the house. If someone were to get a shock in the garage it would trip the rcd in the house and could be reset by someone in the house unaware why it's triped. Hence the 30ma rcd at the garage.
we did warn you .
 
Due to new a new law passed by the iom government you’re no longer allowed to use the term TT unless you have paid and got special permission!
 
I exported my PME to garage 20m odd. Works and tests fine. I have 30ma RCD at house and in the garage at the moment as I didn't have anything else to hand. O o!
 
Thanks for the replies, but what I am asking is about the protection feeding the garage consumer unit? The garage consumer unit has a 30ma rcd and 2 mcb's for lights and sockets. What I don't want is a 30ma rcd feeding another 30ma rcd from the house to the garage. As this is a domestic premises reg 411.3.3 requires additional protection for sockets not exceeding 32A via a 30ma rcd. And reg 411.3.4 requires that AC final ciruits with luminaries requires additional protection via 30ma rcd. As this is not an "AC final circuit" I'm asking what is normally best practice. As it will be a clean run of SWA cable between the 2 is it best to use a switch fuse from the house to the garage or a 100ma rcd and mcb. My thoughts are that an rcd would be the better option. Yes the garage can be a TT system.
 
Here we go again.
There in no need to have an RCD at the house end for this circuit. It’s SWA out to the shed.
Run the SWA from a non RCD way in the house CU, or (even better) from a separate switch/fuse.

There’s no point having a 100mA RCD feeding a 30mA RCD. There’s no telling which will trip if there is an earth fault of >100mA.
You can only discriminate RCDs on the basis of TIME. You would need a time-delayed (S type) RCD at the supply end.
 

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