feed for a garage

[Deleted member 26818]

had my annual assessment today (niceic) and 1 of the jobs was like this.
16th split board in house with tt supply. 4mm 2 core swa on non rcd side to log cabin. 2 way rcd board in cabin. no mention of needing rcd protection on the sub main and its news to me too.

Are you stating that there are non-RCD protected circuits in the above installation?
Is there no front end 100mA RCD?

 

[Deleted member 26818]

I think you are taking minimising inconvenience to the extreme there.

By fitting the RCBO at the CU and you are minimising the inconvenience to to dwelling. Which in my opinion is enough.

Not really, you are suggesting that the RCBO should be installed in the House CU, with an MCB at the garage CU. Total cost about £11.35.
Whereas I'm suggesting the other way round with a total cost of about £11.85.
50p more expensive, without the inconvenience of having to go to the house if the RCD trips, or the attendant loss of lighting.
I would suggest that you are taking the penny pinching to the extreme.

 

[flukey]

Are you stating that there are non-RCD protected circuits in the above installation?
Is there no front end 100mA RCD?

ahh im with you now spin.
we seem to have moved off of the op and are now talking about the incomer.
op is asking whether to 30mA protect his sub main or not.
im back on the same page now.
of course my job has 100mA incomer as you would expect being a tt system, swa is off non rcd side though with 30 mA rcd board in cabin

 

[chiplard]

Not really, you are suggesting that the RCBO should be installed in the House CU, with an MCB at the garage CU. Total cost about £11.35.
Whereas I'm suggesting the other way round with a total cost of about £11.85.
50p more expensive, without the inconvenience of having to go to the house if the RCD trips, or the attendant loss of lighting.
I would suggest that you are taking the penny pinching to the extreme.

The OP asked for ideas on how to feed a garage not the cost involved.

I gave my opinion and the method that i would utilise if I could, you then quoted a reg that i was allegedly not fulfilling.

I then gave a reason why this reg was being fulfilled, now you are quibbling about 50p.

Are we here to give advice or try and prove each other wrong over the smallest thing?

 

[flukey]

The OP asked for ideas on how to feed a garage not the cost involved.

I gave my opinion and the method that i would utilise if I could, you then quoted a reg that i was allegedly not fulfilling.

I then gave a reason why this reg was being fulfilled, now you are quibbling about 50p.

Are we here to give advice or try and prove each other wrong over the smallest thing?

was just thinking the same thing as we managed to bypass the sub main in op and end up at the front end rcd

 

[Deleted member 26818]

Not actually trying to prove anything.
I'm just trying to work out why you would suggest installing the RCD in the house CU, instead of the garage CU.
I cannot see any advantage in doing such, and yes I do believe that it would be in breach of Regulation 314.1.
If perhaps the cost implications were excessive, then I could see an advantage in doing as you suggest.

 

[chiplard]

Not actually trying to prove anything.
I'm just trying to work out why you would suggest installing the RCD in the house CU, instead of the garage CU.
I cannot see any advantage in doing such, and yes I do believe that it would be in breach of Regulation 314.1.
If perhaps the cost implications were excessive, then I could see an advantage in doing as you suggest.

Because if the Garage CU was isolated then there would be no Live/Earth protection on the cable supplying it. You would only have the over current protection offered by the MCB in the main CU.

 

[Deleted member 26818]

Overcurrent protective devices provide both overload and fault protection.

 

[chiplard]

Agreed. But only if the earth leakage is high enough to trip the MCB.

But I would rather RCD protect the cable from the main CU where the only way it can be isolated is if the power to the cable is isolated at the same time.

No Reg dictates this, it is just my personal preference.

 

[davies84]

I agree swa has its own mechanical protection and as such does not have to be rcd protected.