RCD board - which end?

[beemer]

Hi,

I will be installing a supply to a shed at the bottom of the garden for lights and sockets, the customer has already laid down 4mm SWA down the garden, but my question is, do I have a RCD board at the shed end, or the house end of the SWA?

I understand that the logical answer is the house end, to protect against accidental damage to SWA. If this is the case, then do I install a basic non RCD consumer unit in the garage?

Thanks in advance for your help!

Regards

David

 

[Gforce]

I would just have a mcb at house to protect against faults in swa-say a 20 amp for 4 mm swa-then a cu in shed with rcd to cover all circuits.

Bit fine with 4 mm as has been discussed before on here-so watch the number of sockets you use if your using a radial.

 

[a1]

What's the length of the run from the CU to CU in shed, David? What is likely to be used in there?

What is the current earthing arrangment?

 

[NozSpark]

Hi,I will be installing a supply to a shed at the bottom of the garden for lights and sockets, the customer has already laid down 4mm SWA down the garden, but my question is, do I have a RCD board at the shed end, or the house end of the SWA?

I understand that the logical answer is the house end, to protect against accidental damage to SWA. If this is the case, then do I install a basic non RCD consumer unit in the garage?

Thanks in advance for your help!

Regards

David

The normal way of doing this (especially with a SWA sub main) is to RCD at the shed, however every job is different....

If the shed is going to have a fridge or freezer then your customer would probable prefer the RCD at the house with some sort of indication to show the supply is present, but if they were using it for a wood working shop (lathes etc.) they you should use an active RCD at the shed..

 

[batty]

I always put Rcd at shed end. As long as cable is not installed in wall etc although swa can be then this is the best way. The worst thing is having to go all the way to the house to test it and surely the nearer to a fault the better. Swa is unlikely to get damaged as long as it has been installed correctly.

Batty

And if its pme its better to rod shed

 

[Andy™]

Hi,I will be installing a supply to a shed at the bottom of the garden for lights and sockets, the customer has already laid down 4mm SWA down the garden, but my question is, do I have a RCD board at the shed end, or the house end of the SWA?

I understand that the logical answer is the house end, to protect against accidental damage to SWA. If this is the case, then do I install a basic non RCD consumer unit in the garage?

Thanks in advance for your help!

Regards

David

depends on house earthing for where RCD goes.

If house in TN, then MCB at house, RCD at shed. If TT, then RCD will have to be at house, optional to put on in shed, but a waste of time/money

If house supply is TNC-S, then your best making shed TT and make sure SWA earth is separate from rod earth. if house is TNS or TT, you can easily export the earth

Accidental damage to SWA will trip MCB/blow fuse very quickly if TN, if TT, RCD will be needed at house to ensure supply will disconnect incase of fault (spade through cable)

 

[batty]

If its TT I allow in my price to put td Rcd in house and Rcd board in shed. I also TT shed as I think it is a seperate install and should be earthed seperately. Thats the way I do it probably overkill but I don't lose many jobs.

Batty

 

[Andy™]

If its TT I allow in my price to put td Rcd in house and Rcd board in shed. I also TT shed as I think it is a seperate install and should be earthed seperately. Thats the way I do it probably overkill but I don't lose many jobs.Batty

2x RCD's is a bit overkill, but then if its more unlikely for both to fail.

And whilst were on about TTing sheds from TNC-S... we all know of the dangers of PME, but does anyone know of any shocks received by someone touching an PME earthed appliance and a TT earthed appliance? (like one appliance plugged into house and one into shed?) probably bit more of a shock than standing on the ground and touching a PME earth

 

[steptoe]

2x RCD's is a bit overkill, but then if its more unlikely for both to fail.And whilst were on about TTing sheds from TNC-S... we all know of the dangers of PME, but does anyone know of any shocks received by someone touching an PME earthed appliance and a TT earthed appliance? (like one appliance plugged into house and one into shed?) probably bit more of a shock than standing on the ground and touching a PME earth

I know of a horse got killed from an exported PME to a stable.

 

[batty]

I know of a horse got killed from an exported PME to a stable.

Good reason not to have pme on agricultural sites.

Batty

 

[Apache]

Good reason not to have pme on agricultural sites.Batty

Horses and cows are very sensitive to stray voltage. They don't wear rubber wellies or shoes you see

Stray voltage is a bit issue in milking parlours (if any of you have done any of this?!). They tell me 12V can kill a cow if you are unlucky. I know of a cow that was killed instantly by a faulty electric milk pump. Stone dead in the milking parlour. That made the farmer's morning......

 

[batty]

Horses and cows are very sensitive to stray voltage. They don't wear rubber wellies or shoes you see Stray voltage is a bit issue in milking parlours (if any of you have done any of this?!). They tell me 12V can kill a cow if you are unlucky. I know of a cow that was killed instantly by a faulty electric milk pump. Stone dead in the milking parlour. That made the farmer's morning......

Yes I know a farmer that lost a few cows to a faulty water heater.

Batty

 

[beemer]

What's the length of the run from the CU to CU in shed, David? What is likely to be used in there?What is the current earthing arrangment?

Length of run about 20m

A shed light and power for ELV garden lights.

TN-S

May have to fit sub board as no spare ways in existing board.

Thanks for all your replies

 

[batty]

Length of run about 20mA shed light and power for ELV garden lights.

TN-S

May have to fit sub board as no spare ways in existing board.

Thanks for all your replies

I like to put sub board in on outbuildings as it makes it easy to isolate supply if neccessary. We do get strong winds now and then and with global warming things could get worse.

Batty

 

[Andy™]

but will still need something at the start to protect the cable...

 

[batty]

Sorry I meant 1 or 2 way consumer unit at house end.

Batty