feed for a garage

[flukey]

this job would be notifiable too so if your not registered with a scheme dont forget to give your labc lots of your hard earned

 

[chiplard]

If you have the space in your existing CU then fit an RCBO, run SWA underground not forgetting to earth the armour at the supply CU. A CU with main switch and relevent MCB's will then suffice in the garage.

You will obviously need to do the relevent tests on the submain as well as the individual circuits within the garage.

 

[Deleted member 26818]

If you have the space in your existing CU then fit an RCBO

Why would you say this?
Is there a cost saving perhaps?
To do such would breach Regulations in BS7671, specifically 314.1 parts (i), (iii) and (iv).

 

[chiplard]

If you run the garage from an existing board fitted with an RCD then a problem in the garage would cause problems with other circuits in the house being tripped. By running from an RCBO then the house would be unaffected.

 

[Deleted member 26818]

If you run the garage from an existing board fitted with an RCD then a problem in the garage would cause problems with other circuits in the house being tripped. By running from an RCBO then the house would be unaffected.

Yes it would, just as would using an MCB at the house.
The difference being, that if anything in the garage caused the RCBO to trip, you would have to go back to the house to re-set.
Using an MCB in the house, and an RCBO in the garage CU would allow you to re-set without having to go to the house.

 

[chiplard]

Yes it would, just as would using an MCB at the house.
The difference being, that if anything in the garage caused the RCBO to trip, you would have to go back to the house to re-set.
Using an MCB in the house, and an RCBO in the garage CU would allow you to re-set without having to go to the house.

I'm sorry but i cant see the problem and why this contravenes 314.

 

[mart8235]

a distribution circuit should not be on a rcbo or rcd (unless tt system)
with an swa the armourings must be earthed and there you have your protected cable. rcd dist board in garage.
not sure what all the fuss is about?

 

[flukey]

a distribution circuit should not be on a rcbo or rcd (unless tt system)
with an swa the armourings must be earthed and there you have your protected cable. rcd dist board in garage.
not sure what all the fuss is about?

why does an swa have to be rcd protected if on a tt supply

 

[Deleted member 26818]

I'm sorry but i cant see the problem and why this contravenes 314.

Quite simple, 314.1i) requires us to minimise inconvenience in the event of a fault.
What is more convenient, re-setting an RCD in the garage, or re-setting an RCD in the house.

 

[Deleted member 26818]

why does an swa have to be rcd protected if on a tt supply

To provide earth fault protection.

 

[chiplard]

Quite simple, 314.1i) requires us to minimise inconvenience in the event of a fault.
What is more convenient, re-setting an RCD in the garage, or re-setting an RCD in the house.

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.

 

[mart8235]

why does an swa have to be rcd protected if on a tt supply

100mA RCD for the whole install!!!!!

 

[chiplard]

a distribution circuit should not be on a rcbo or rcd

What reg states that.

My last assessment was a Garage install with RCD at house CU, the assessor was quite happy with it.

 

[flukey]

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.

 

[SirKit Breaker]

I would put in a henley block and split the supply. Shove your existing meter tails into it, and fit a metalclad switch fuse for the garage. Shove some new tails from henley block to switch fuse, then run the appropriate sized 3 core SWA out to the garage. in the garage fit a metalclad consumer unit. Depending on what your intentions in the garage are i would fit a consumer unit with a 100A DP isolator and RCBO's for the individual circuits, or a 100A 30mA RCD incommer and MCB,s for the circuits, its up to you really. By doing it this way the garage install will have no effect on the existing, and vice versa in the event of a problem.
There are other things to consider, but without seeing it i cant comment. But if you are going a fair way i would shove an earth spike in as well.

Cheers........Howard