Discuss PME for farm buildings in the Electrical Wiring, Theories and Regulations area at ElectriciansForums.net

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Mark.W

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Hi chaps

In need of some advice please!

I'm on a job at the moment (installing 50kw PV) where the customer is upgrading his supply with Western Power! He currently has a 100A 3ph supply and his new supply will be 250A 3ph! The customer has a dairy farm! The existing earthing arrangement is PME! On Monday I was having a chat with one of the lads from Western Power who said that the new supply would be PME but I have to TT my PV install. Now today another Western Power burke comes along and says the whole install must be TT because the regs state farm supplies have to be TT?! Is this true?! I never knew farm buildings HAD to be TT!

Regards
Mark
 
It is recommended that PME is not used for areas used by livestock, it can be used, but the bonding requirements are complex and extensive (metal grids in the floor etc..etc,,).

It works out far easier and cheaper to TT it, I would suggest you get a copy of GN7.
There are other differences to RCD requirements for farms too.
 
Last edited:
Great idea PME was, long live TNS, 3 cores for three purposes, oh hang on, i forgot, the laws of physics changed around about when there was a realisation it was cheaper to use a smaller cable to each house
 
Sorry was a rant I hijacked your thread. I apologise.

it was in reference to your issue, it just reminded me about how pants PME can be, and am sure it was to do with cost cutting that it was introduced, not safety.

hence the cynical "the laws of physics" changed bit!
 
With the existing supply being PME I would presume that all bonding requirements would be in place!

Another thing to add is the new supply is about 10m from the house electrics! I installed a 250A fused isolator in the middle then onto a 300A busbar then fused down to 100A for the house and 80A for the PV! Western Power's burke has now told me to downrate my 250A fuses because it cannot be the same size as theirs, but if I do that I'd have to change the whole unit because the next size fuse which is 200a wont fit!

Your thought please!
 
No, the bonding requirements for the livestock areas are completely different, there is no second guessing, you really need GN7 to see how it should be done.

The requirements for PME are very complex for this area. and will work out very expensive due to the amount and size of the conductors.

Sorry I made a mistake earlier (now edited) it is GN7 you need.
 
As my father in law repeatedly said "never assume anything as all you will do is make an --- out of u and me"
They probably want discrimination between their service fuse and your isolator fuse, ergo the fusing down req...
 
With the existing supply being PME I would presume that all bonding requirements would be in place!

Another thing to add is the new supply is about 10m from the house electrics! I installed a 250A fused isolator in the middle then onto a 300A busbar then fused down to 100A for the house and 80A for the PV! Western Power's burke has now told me to downrate my 250A fuses because it cannot be the same size as theirs, but if I do that I'd have to change the whole unit because the next size fuse which is 200a wont fit!

Your thought please!

I'd do a bit of searching for those 200 amp fuses....I'd think there is something available.
 

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