PME supply

[ElectricalAsh]

Hi All,

Could anyone tell me why you can't have a PME supply within a metal garage/shed?

 

[Engineer54]

Hi All,

Could anyone tell me why you can't have a PME supply within a metal garage/shed?

Who told you that you can't have a PME supply within a metal shed/garage??

 

[tony mc]

Whats wrong with having PME in a metal garage or shed !

If the garage or shed is a extraneous conductive part and as long as the bonding is in place as per table 54 why not!

 

[Deleted member 9648]

Oh dear......not this old chestnut back from the grave.

ElectricalAsh......Have a look in bs7671 and see where it says you cant use a PME supply for an outbuilding...it says no such thing.
The reason sometimes it pays to TT such an installation is that if there are extraneous CP's which will require main bonding PME regs apply...ie-minimum 10mm back to the MET. If the shed is fed in 4.0mm SWA for example this may mean a separate 10mm g/y would be required back to the MET...not really practical. It may be simpler to separate and TT the shed. If there are no ECP's it would always be preferable to use the PME earth if available.

 

[ElectricalAsh]

Western power have installed a new 3 phase supply and have said that they can't provide PME as it is within a metal shed. So have provided a TT supply. I can't see a problem with a PME supply so wondered if anyone new the reason? It is not another question about exporting a PME to an outbuilding as you say that has been covered many times before.

 

[MDJ]

Well they are the suppliers, if they won't provide it even if there is no reason within the BGB then you will have to live with it, I may check the BGB out later myself to see if there is a reason why not, Can't think of a reason why it's a problem as yet, however there may be a rule which you may be able to challenge them or not about this, But it is Saturday night and probably won't put it first priority on my list.

 

[Chr!s]

What sort of metal shed are we talking about here?

 

[ElectricalAsh]

Well it's more like a unit about 50m x 50m the customer has had the supply moved from his house into the unit as he is knocking the house down. When I ask the guy installing the cutout if they would be supplying an earth he said they can't PME as its within a metal shed. They have also brought a separate earthing conductor into the cutout. Just seemed strange.

 

[Deleted member 9648]

Western power have installed a new 3 phase supply and have said that they can't provide PME as it is within a metal shed. So have provided a TT supply. I can't see a problem with a PME supply so wondered if anyone new the reason? It is not another question about exporting a PME to an outbuilding as you say that has been covered many times before.

TBH it would have been helpful if that info was in the OP......Like you I'm stumped as to their reasoning....as most industrial units are in effect big metal sheds,and they all get PME supplies.

 

[Chr!s]

Well it's more like a unit about 50m x 50m the customer has had the supply moved from his house into the unit as he is knocking the house down. When I ask the guy installing the cutout if they would be supplying an earth he said they can't PME as its within a metal shed. They have also brought a separate earthing conductor into the cutout. Just seemed strange.

How many supplies to the unit?

Any other units?

Does the house still have a supply, any shared services?

 

[Engineer54]

As wirepuller stated, the majority of small to medium industrial/commercial units built today are steel framed and clad structures, that seem to have no problem being supplied by the DNO's with PME single and 3 phase supplies... Even if it was a special industrial unit, the DNO can provide a sudo TN-S supply derived from a PME network.


Might be worth getting in touch with the DNO Area Manager to find out the reasoning!!

 

[Plonker 3]

But the DNO doesn't have a obligation to provide a earth.

 

[Engineer54]

But the DNO doesn't have a obligation to provide a earth.

They may not have an actual obligation to provide an earth point, but i've been informed that the DNO's across the country are supposed to have a policy now, that they ''Will provide'' an earth point when a system earthing means is available.

 

[Knobhead]

Well it's more like a unit about 50m x 50m the customer has had the supply moved from his house into the unit as he is knocking the house down. When I ask the guy installing the cutout if they would be supplying an earth he said they can't PME as its within a metal shed. They have also brought a separate earthing conductor into the cutout. Just seemed strange.

Instead of taking note of the jobsworth who installed the head, talk to Western Power. In other words speak to the organ ginder.

 

[ElectricalAsh]

Thanks all for the replies I'm back there in the week so will contact western power to see if I can get a reason.

 

[Steve_P]

Western Power can be a pain in the whatsits. Have you got the number of the local office? If you have phone them direct. The guys in the office are usually switched on, it's the central number and some of the jobsworths that come out that need a kick.

 

[richy3333]

Are they arguing the building is not a permanent structure and won't supply an earth because of this as per ESQCR?