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Posted By Topic: Replacing main earth in MEN out building

May 24 2017 08:44

This property consumer mains connects to a free standing meterbox/distribution box which feeds three out buildings, a house a two sheds. In the box there is a common earth/neutral connection. There is a MEC connected to an earth peg next to the distribution box. Each out building submain is protected by fuses.

The out building submains are supplied with PEN (no seperate earth) and each outbuilding sub board has a MEC connected to an adjacent earth peg.

The house switchboard is to be upgraded without relocation and this includes replacing the house MEC and earth peg. The house is certainly an MEN switchboard but isn't the first MEN switchboard, or is it? Running a PEC from the first board isnt practical. All work will be carried out by licensed workers.

My question, is replacing the house earthing system mains work that requires inspection?

May 24 2017 09:02

So you have an MSB supplying 3 "outbuildings" via PEN submains.
All kosher.
Installing each of the outbuilding "main earthing systems" would have been "mains work", and therefore high risk PEW requiring inspection.

Replacing the main earthing system for any of these outbuildings is replacing fittings; therefore classed as low risk PEW.

Replacing a PEN submain with one including a PEC would be an alteration, but not mains work; so general PEW.


May 24 2017 12:33

You say that at the meter location there is "a common earth/neutral connection", but is there a MEN link?

May 24 2017 12:39

There's a N-E link.
It's at what is, by definition, the MSB; and there's an MEC connected there as well, running to adjacent electrode.
So I'd say it's an "MEN link"; and part of a "main earthing system"

May 25 2017 07:31

Thanks guys. Seems I answered my own question in the title. "Replacement" in this case is low risk equals no inspection. We have to upgrade SERFs to RCD+MCB so the whole job will be general and covered by COC.