Garage Supply (SWA feed + 2 Way CU)

[timo]

Evening all.

Got a job coming up soon, supply to a garage 35 meters away from exitsing CU. Plan on spliting the tails and taking a SWA via a isolator and 32A MCB unit to the garage. At the garage will be a 16A for socket raidel and 6A for lighting points.

Questions
Am i right in that the SWA does not need RCD protection from the isolator to the gaage cu (protected for OC and SC by 32A MCB)

I have worked VD at around 8.5v does the 6.9 v limit apply to this circuit as the garage will have light points or does 11v max apply as this is a supply cable?

Eathing - Will the 6.0mm earth from the SWA be ok as earth or will i need to spike? (TN-S at house incomer)

 

[Guest123]

Hi.

As you have a TN-S supply, no need for a rod, the earthing system of the house is fine to use.

The sub-main itself doesn't need RCD protection.

The VD limit is 3% (6.9V) as you are supplying lighting circuits at the end of it.

 

[Mr Mark Sparks]

and providing there are no main sevices in the garage then the 6mm is ok as cpc

 

[timo]

Cheers fellas

 

[Johno]

i agree

 

[Mr.Black]

I thought if the swa is being buried then it should be rcd protected,as its probably running through the garden it will be a special installation.

 

[timo]

I thought if the swa is being buried then it should be rcd protected,as its probably running through the garden it will be a special installation.

SWA isnt been burried.

Anywhere outside is a specical location, above or below. But not sure now if RCD is needed? or is it cos of the good protection of the swa no rcd needed. but final circuits will be 30Ma protected.

 

[Guest123]

There's no requirement in BS 7671 to RCD protect a buried SWA cable in any location/situation.

It must be correctly installed though, there is a reg....522-8-10, also 522-6-2 refers.


Edit.....thought I'd better just add, "unless it's a TT system" to avoid confusion.