17th edition board, one circuit feeding a board in a out building.

[Edwardioo]

a friend of a friend has the above, so the board in the shed has a rcd and obviously the 17th edt board does to, but if if there was to be any fault in the shed its going to trip the rcd in the house (17th Edt) whats the best way round this, i was thinking some how having its own main switch for the shed but im not sure how any feedback would be great. The reason i'm asking this is because its happened, and then they dont have power indoors.

 

[telectrix]

the feed to the shed needs to be in SWA and taken from a non-RCD way in the house CU. the way it is as you describe, you have 2 RCDs in series and so no discrimination, so in the event of a fault in the shed , either or both would trip.

 

[Guest123]

Is the 17th board a 'high integrity' one....i.e....a couple of non RCD protcted ways available in it???

What cable is the distribution circuit run in...T&E, SWA etc???

What earthing system is present???

 

[Edwardioo]

Is the 17th board a 'high integrity' one....i.e....a couple of non RCD protcted ways available in it???

What cable is the distribution circuit run in...T&E, SWA etc???

What earthing system is present???

its a 8 way 2 rcd, 3 ways taken on each side, and there isnt a few ways that arnt protected by an rcd :/ its an eton board, its tncs, its wired in swa as it is a new installation by an nic eic firm and only done recent. somehow that circuit needs to be taken out so it isnt protected by an rcd in the house, but the board in the garage has an rcd and is a 6 way board i think.

 

[DurhamSparky]

remove shed RCD fit 100A isolator
remove MCB from house box and install RCBO after the Main switch and reconnect!!

 

[Ponty Massive]

remove shed RCD fit 100A isolator
remove MCB from house box and install RCBO after the Main switch and reconnect!!

I'd just remove the RCD in shed, that way the RCD in the board is protecting the supply cable as well.

By putting a RCBO on the RCD board, you will still have the discrimination problem.

 

[DurhamSparky]

NAH!! re-read my last sentence!!

remove MCB from house box and install RCBO after the Main switch and reconnect!!

that way you have installed a RCBO on a unprotected way!

 

[Edwardioo]

Cheers the help!

 

[spark 68]

Hi Durham,

remove shed RCD fit 100A isolator
remove MCB from house box and install RCBO after the Main switch and reconnect!

That won't be any better than he already has, as you will have the RCBO in series with the RCD in the board (op said the board is only is only two way).

One way would be, henley blocks, second set of tails,Isolator and MCB in seperate enclosure and leave the current shed CU as it is.

Obviously the feeder MCB would need to be calculated to the cable supplying the shed and try to achieve discrimination with the MCB's in the shed CU.

 

[Guest123]

its a 8 way 2 rcd, 3 ways taken on each side, and there isnt a few ways that arnt protected by an rcd :/ its an eton board, its tncs, its wired in swa as it is a new installation by an nic eic firm and only done recent. somehow that circuit needs to be taken out so it isnt protected by an rcd in the house, but the board in the garage has an rcd and is a 6 way board i think.

Ok, SWA distribution circuit on TNCS does not require an RCD.

As there aren't any non RCD ways in the house DB, you'll have to install a small one way DB for the distribution circuit and break into the tails using service blocks to supply this new DB.

Inside this DB you'll need a standard BSEN 60947-3 100A main switch with an MCB sized to suit the distribution cable.

The shed will not then have any effect on the house DB at all.

Also, the RCD in the shed should remain to protect the circuits within.

 

[Edwardioo]

Ok, SWA distribution circuit on TNCS does not require an RCD.

As there aren't any non RCD ways in the house DB, you'll have to install a small one way DB for the distribution circuit and break into the tails using service blocks to supply this new DB.

Inside this DB you'll need a standard BSEN 60947-3 100A main switch with an MCB sized to suit the distribution cable.

The shed will not then have any effect on the house DB at all.

Also, the RCD in the shed should remain to protect the circuits within.

Ahh i see, i dont understand why this wasn't done when the two boards were done, cheers for the help!

 

[Edwardioo]

NAH!! re-read my last sentence!!



that way you have installed a RCBO on a unprotected way!

there is no unprotected ways mate, just 17th edt 8way board with obviously two rcd's

 

[Edwardioo]

I'd just remove the RCD in shed, that way the RCD in the board is protecting the supply cable as well.

By putting a RCBO on the RCD board, you will still have the discrimination problem.

But then if a fault occurs in the shed and trips rcd off in the house half of the power will be lost! which i dont want!

 

[DurhamSparky]

when you remove the MCB you will have created a free way...!! shimmy the RCD along and install a piece of busbar from L out on main switch to feed your RCBO...!

what model CU have you got!! is teh Main switch in the middle or to the side!

 

[Edwardioo]

when you remove the MCB you will have created a free way...!! shimmy the RCD along and install a piece of busbar from L out on main switch to feed your RCBO...!

what model CU have you got!! is teh Main switch in the middle or to the side!

eaton board m/s in the middle, and two rcd's either end of the board.

 

[DurhamSparky]

BINGO!!! smaller version of this!!

you can install RCBO to the right hand side of main switch!! as i mentioned little piece of busbar and your away!

 

[spark 68]

I still think it would be better (safer?) to have the RCD/RCBO local to the shed, as it is easier to reset rather than having to walk back to the house to reset each time.

 

[Edwardioo]

BINGO!!! smaller version of this!!

you can install RCBO to the right hand side of main switch!! as i mentioned little piece of busbar and your away!

ahh i see but the existing bit of busbar would be in the way, would i just cut it and then put a piece from L from main switch and wack the rcbo on?

 

[DurhamSparky]

Yup...!!

 

[Edwardioo]

Yup...!!

is this the correct way of doin it then?