secondary DB !!!

[Murdy]

My pal has asked for a power supply for lights and sockets in his garage and so can I just ask if the following would be ok ???

32A MCB at the main CU to protect garage feed.
2.5mm SWA run of 30m to the garage
Secondary CU in garage with 1 20A radial for 3 socket outlets and 1 6a lighting circuit.

considering volt drop over this length would I need to up the SWA to 4mm or should 2.5 do ??

cheers

 

[Hawk81]

well for a start the 2.5mm should not be on a 32amp mcb. If you want to give him a 32amp supply then it should be 4 or 6mm.

 

[Murdy]

Other than changing the 2.5mm swa to 4mm then I presume the rest is fine ??

 

[johnboy6083]

make sure there is an RCD/ RCBO in the garage CU.

 

[Murdy]

yeah... both the cu in the house and the garage have rcd's
.

 

[cornburn]

yeah... both the cu in the house and the garage have rcd's
.

With discrimination between them?

 

[Steve D]

Just a quick point here on the discrimination of RCDs.
If you have an RCD at source and then also at the secondary DB, then I reckon you need a time delayed one at source so that if there is an earth fault on one of the garage circuits then the RCD nearest the fault will trip.

However, If you've got a time delayed RCD at the main CU, does that still meet all requirements of additional protection for the other circuits connected to the main CU? I'm guessing it does ?

 

[pushrod]

Easiest way, if it is possible, is to arrange the house CU so that the distribution swa is not protected by an rcd and just have the rcd in the submain.