Another random question

[hightower]

Pretty sure you all know by now I like to dream up random scenarios.

So let's say running SWA to an out building, but the consumer unit is a tricky run that would make it difficult to get SWA all the way to it. Would you then run T+E say from the consumer unit, through the external wall to some form of IP rated junction box, and then join the SWA in this external junction box?

 

[telectrix]

If the garage socket & outside socket were incorporated as 1 ring final circuit why couldn't you just add a FCU for the lighting to be down rated?

could be donelikethat, butthe problem you would always have is a fault in the garage would trip the RCD on the house RFC, thus entailing a trip back to the CU from the garage whenever you plugin your old faulty drill/leccy fire/welder/kettle/whatever.

 

[Skimpy Wan]

They'll just have to remember to leave the back door unlocked then! Lol

Another question then ...

If the garage is separate to the dwelling how do you supply this and on what type of earthing system (I.E. TN in dwelling and a TT for garage)?

 

[hightower]

could be donelikethat, butthe problem you would always have is a fault in the garage would trip the RCD on the house RFC, thus entailing a trip back to the CU from the garage whenever you plugin your old faulty drill/leccy fire/welder/kettle/whatever.

Which leads on to another question I had. Let's say there's a whole new distro circuit to be ran to a garage. You run a cable to a spare way on your rcd protected board, and then on to the distro board in the garage. Brilliant because you can now split the garage circuits however you like, except any earth fault is still going to trip the rcd at the supply board, meaning a trip to the board in the dark.

I'm guessing the trick is to run it from an s type rcd so there's some discrimination, but the few I've come across haven't been wired like that.

 

[telectrix]

always extend the TN earething to the garage unless eatraneous parts in garage can't have adequate bonding due to size of supply cable from CU ( i.e. where 10mm bonding is required on a PME system)

 

[Skimpy Wan]

Similar thought process!

My concern with a time delay RCD in the house is that all circuits would then be time delayed in the dwelling (hence my query about making the garage a TT system)?

 

[telectrix]

Which leads on to another question I had. Let's say there's a whole new distro circuit to be ran to a garage. You run a cable to a spare way on your rcd protected board, and then on to the distro board in the garage. Brilliant because you can now split the garage circuits however you like, except any earth fault is still going to trip the rcd at the supply board, meaning a trip to the board in the dark.

I'm guessing the trick is to run it from an s type rcd so there's some discrimination, but the few I've come across haven't been wired like that.

as long as the cable from the CU to the garage does not require RCD protection ( e.g. SWA or cables inside house are not buried<50mm deep ) then feed from a non=RCD way in a hi integrity board or split tails before CU ( this would entail fitting a 2 pole isolator befor the split if not already in situ, and a separate OCPD for the garage feed.).

 

[ruston]

Split the tails , armour direct to metal clad switched fuse, direct to shed . No need for RCD at supply end.

 

[hightower]

as long as the cable from the CU to the garage does not require RCD protection ( e.g. SWA or cables inside house are not buried<50mm deep ) then feed from a non=RCD way in a hi integrity board or split tails before CU ( this would entail fitting a 2 pole isolator befor the split if not already in situ).

The installs I've seen (not ones we've done, ones we've come across) all seem to come from a 40a breaker or done such on part of the rcd protected

 

[telectrix]

The installs I've seen (not ones we've done, ones we've come across) all seem to come from a 40a breaker or done such on part of the rcd protected

only problem there is as i said in post #16.

 

[hightower]

only problem there is as i said in post #16.

Yeah hence why it's been chewing me to bits - surely not the best practice

 

[Leesparkykent]

If the house is TT then the distribution circuit may need to be on an RCD due to high EfLI.

 

[Deleted member 26818]

I'm guessing the trick is to run it from an s type rcd so there's some discrimination, but the few I've come across haven't been wired like that.

If the RCD has been installed to provide additional protection for sockets, cables concealed in walls or circuits of a location containing a bath or shower, it will not be an 'S' type.