Additional RCD Required?

[craig1000]

Hi,
i have ajob to complete which is to urgrade existing DB in a stables & then install small power & lighting. The work is in a external stable block of a equine vets. Off of this existing DB which i am to upgrade shall also be another barn/store outbuilding & another work shop outbuilding.
Now as the elctricity supply comes into the stable block & at this point is where i shall be changing the Db to a 17th dual rcd db so all circuits off of this are rcd protected. The question is where the swa i am running into the barn/stores seperate db does this db also need to be a rcd db/protected, as technically it plus its circuits are already rcd protected by the rcd on the board in the stable block,correct? or not? or should i as good practice install a rcd board in there anyway. At eh moment it has a non rcd db in there, doed it need upgrading?
Sorry if i confuse with my wording & please accept my apoligies if you feel i should know this but i dont & its better to ask than do/assume & have things wrong!
Thankyou in advance!
Craig!

 

[Engineer54]

Need more information, like what type of supply do you have?? I would install an S type RCD to the supplies being taken to other outbuildings, you can then install normal CU/DB units with 30mA protection for the various circuits being supplied by that CU/DB...

Personally, with this being a stable, and a veterinary stable at that, i would be inclined to be using RCBOs in those CU/DB's rather than 17th dual RCDs for several reasons...

 

[craig1000]

Supply is a single phase 2 wire tncs supply, havnt been able to check suplly authoritys fuse but am assuming a bs3161 type 1 or 2? 100amp supply ? these are things i have been unable to confirm.
What other infor would you rewuire to pass a better judgement? would you mind eleborating on the several reasons why rcbos rather than 17th dual rcbos?

 

[Engineer54]

Supply is a single phase 2 wire tncs supply, havnt been able to check suplly authoritys fuse but am assuming a bs3161 type 1 or 2? 100amp supply ? these are things i have been unable to confirm.
What other infor would you rewuire to pass a better judgement? would you mind eleborating on the several reasons why rcbos rather than 17th dual rcbos?

Each individual circuit would then have it's own RCD protection, which is far more stable than an RCD protecting several circuits, especially where 4 legged animals are concerned.
Easier faster fault diagnosis, any tripping or more importantly, ''non tripping'' failures affect just the one circuit. Do i really need to go on, cause my grey matter hasn't quite switched in yet?? lol!!

If PME single phase supply, then always run your sub-mains with a third core. Better to use 10mm SWA for those sub-mains too, to save you running in, a separate bonding conductor where extraneous metalwork such as water pipes etc, are present, and use the SWA as your CPC...

 

[Deleted member 26818]

Unless there is a bonded metal grid in the floor of the stables, TN-C-S is not recommended.
All circuits, must be protected by a minimum 300mA RCD, including the distribution circuit to the stables.

 

[craig1000]

cheers for your advice guys, much appreciated!

 

[UKMeterman]

TNCS does not sound a good idea regarding horses... Just take a look at stray voltage and the Newbury race course incident..

 

[craig1000]

Regarding the incoming supply then as that is all that is there & is existing as the incomer from the distribution company what do you reckon i do. Do i need the incoming supply changed by the supply company? do i inform the customer of this & or include it in the price after first contacting the supply company for this?