PME system / mods

[nick smith]

I need to gen up about the above system to see if mine is as it should be - is there a FAQ on PME systems somewhere and can I do a system out to a shed with a RCD board in the shed for "extra" safety ?

Nick

[Martin Angove]

What is it that you are concerned about? A more specific question might get a more specific answer. Here are some generalities:

PME is a system where the earth is tied to the neutral at the incoming supply. This gives you an excellent earth impedance so that earth faults can easily trip breakers, but does lead to other "difficulties" which is why there are strict rules governing bonding and so on, and stickers on the incomer saying something like "the supplied PME terminal should not be connected unless the installation fully conforms to the PME requirements of BS7671".

For full details you really need to read and understand "The Regs" (BS7671) but all the practical information is contained within the IEE's OnSite Guide which is available at all large booksellers (try Amazon for example).

The system earth on a PME system is so good that you *may* be able to export it to a shed, so long as the cable is sufficiently rated and the distance isn't too far. If the numbers don't stack up then you will need to install an earth rod at the shed end and protect everything with an RCD.

HTH

Hwyl!

M.