Bonding to a Barn

[Piratepete]

Hi Guys
Customer has asked me to put a socket on the steel column of an open cattle barn (rubble floor) which is 35m away from the garage unit (installed in a wooden shed TN-C-S from the house). It's for trace heating on the water pipe feeding a cattle trough.

I'll run SWA to it, IP65 socket, but bonding the steelwork is a problem.

I could TT the garage unit and run a 6 sqmm alongside the swa (part buried, part fixed to fence) I think.

Any better ideas?

Cheers
Pete (I hate farm jobs)

 

[MarkieSparkie]

Agricultural locations are harsh environments and prone to mechanical damage and corrosion. Rats and mice are a major problem on farms, particularly where hay and straw are stored; and livestock need to be protected from electric shock. Socket final circuits <32A need to be additionally protected by a 30mA RCD.
TN-C systems must not be used for agricultural supplies. 704.411.4
All exposed-conductive-parts and extraneous-conductive-parts that can be touched by livestock must be supplementary bonded. Unless a metal grid is laid in the floor, the use of a PME earthing terminal is not recommended. 705.415.2.1
Rodents will attack all types of cabling, thus galvanised metal conduit and fittings are recommend.

 

[Piratepete]

Agricultural locations are harsh environments and prone to mechanical damage and corrosion. Rats and mice are a major problem on farms, particularly where hay and straw are stored; and livestock need to be protected from electric shock. Socket final circuits <32A need to be additionally protected by a 30mA RCD. Etc, etc

plus IP44 (IP65 in practice)
Yea. I know all this. It explains why a lot farmers around here do their own wiring and sod the regs because they can't b....y afford to comply!

Re: The particular problem - The garage unit (which I'm installing replacing the existing direct supply from the farmhouse to a socket) does have an rcd in it. SWA will be far more durable than conduit in this situation.
Do I have to take the extraneous conductive part bonding all the way back to the earth point in the shed or could I bond to the earth on the socket? It's what you'd do in a bathroom.
Pete

 

[Richard Burns]

plus IP44 (IP65 in practice)
SWA will be far more durable than conduit in this situation.

How will SWA be more durable than galvanized conduit? Just for information.

Would you not be able to use the steel of the SWA and the cpc core as a combined earthing and bonding conductor back to the shed CU?
If using 3 core 2.5mm PVC SWA you would have 10mm2 Cu equivalent (but not if using XPLE).
However in farm environment may degrade fast.

 

[ackbarthestar]

Hi Guys
Customer has asked me to put a socket on the steel column of an open cattle barn (rubble floor) which is 35m away from the garage unit (installed in a wooden shed TN-C-S from the house). It's for trace heating on the water pipe feeding a cattle trough.

I'll run SWA to it, IP65 socket, but bonding the steelwork is a problem.

I could TT the garage unit and run a 6 sqmm alongside the swa (part buried, part fixed to fence) I think.

Any better ideas?

Cheers
Pete (I hate farm jobs)

An open cattle barn with a rubble floor? ...... umm.

IMO, SWA cable out to the Barn, difficult to use Galv conduit (although probably able to withstand a spade) in this situation unless it can be mounted securely off the ground; into an insulated RCD protected CCU with an earth rod and main protective bonding to the metal structure. Check the continuity between the RSJ's and apply extra bonding where required.
Final circuits need to be kept above cattle rubbing height.