S type RCD

[PB1]

Hi all, I am rewiring my house and have a twin 30ma RCD consumer unit in the house, and a single RCD 30ma unit in the garage. The garage unit is fed via 6mm cable from a 40amp breaker in the main unit. When testing the garage unit rcd, that garage rcd and house rcd both tripped because there is no discrimination between the two. I would like to replace one of the house rcds with an S type rcd to prevent tripping in the house CU if a fault occurs in the garage circuits.
However, if I do does this mean that the rest of the house circuits protected by that rcd no longer comply with regulations as presumably the rcd protecting them will not disconnect within 200ms in the event of a 30ma fault?
If that is the case, then what is the best way around this problem? Thanks in anticipation for your help.

 

[telectrix]

feed the garage from a non-RCD protected way. if you don't have this in the CU, split the tails and fit a separate 40A MCB.

 

[Hawk81]

What type of cable feeds your garage? Is it swa or t&e?

 

[PB1]

What type of cable feeds your garage? Is it swa or t&e?

It's T&E

 

[Hawk81]

Well depending on installation method you might not be able to do what tel has suggested.

 

[PB1]

feed the garage from a non-RCD protected way. if you don't have this in the CU, split the tails and fit a separate 40A MCB.

I don't have any non-RCD protected ways, so I think your second suggestion is the way forward. thanks Tel.

 

[Hawk81]

Depending on installing method you may still need a 30mA RCD at house end of garage supply

 

[PB1]

Depending on installing method you may still need a 30mA RCD at house end of garage supply

Ah yes, if it's concealed in a wall less than 50mm deep. Yes it is for just the first couple of metres. Thanks Hawk. Could I fit a small enclosure with an S type 30ma RCD, and a 40amp MCB fed from the split tails and use that to feed the garage supply?

 

[Hawk81]

I don't think that would be right.

 

[Deleted member 9648]

Fit a main switch to the garage CU and use the RCD at the supply end in your enclosure fed from the split tails...with overcurrent protection as well of course.

 

[Richard Burns]

Ah yes, if it's concealed in a wall less than 50mm deep. Yes it is for just the first couple of metres. Thanks Hawk. Could I fit a small enclosure with an S type 30ma RCD, and a 40amp MCB fed from the split tails and use that to feed the garage supply?

Better and cheaper to use a small CU from split tails with a 30mA RCD and 40A breaker and replace the garage RCD with a main switch (use the 30mA RCd in the house), it would mean coming back to the house to reset the RCD but at least it would protect all the cables correctly.
Also you would only need to buy a main switch 3/4 module CU.

As wirepuller said, far too slow!!

 

[PB1]

Thanks for your helpful replies chaps.