Main earth

nee · Mar 9, 2012

Just been asked to do a EICR on a neighbours house who is selling it, nipped round just to have a quick look.
checked the board 16mm main earth on a PME. 10mm earth to gas and water ok. also found that a earth rod had been installed outside at the side of the house. its on an housing estate in a typical semi-detached house. Always thought you should never combine systems!! and have never come across it before. So will recommend that only one system is used, any advise???:blush5:

needasparks · Mar 9, 2012

you say neighbours house so i guess yours has a similar supply (TN/TT ?) Does it seem like someone has done a diy pme to get the earthing better if was original TT. Only you can answer that from what your presented with.

SPARTYKUS · Mar 9, 2012

If its PME it won't hurt anyone if theres a rod as well. In fact removing it won't hurt either. So do either or neither

telectrix · Mar 9, 2012

might have been originally TT, then was PME'd and the rod left in. as spartykus says, either way no problem.

Octopus · Mar 9, 2012

My guess is that the house didn't have a main earth, somebody installed a rod as a temporary "fix" then the DNO came along and made it PME, leaving the rod in place.

nee · Mar 9, 2012

HI, got mine on a TT readings are fine, so wouldn't really think they would have had a problem with just a TT, just the thought of combining the two systems

Edd · Mar 10, 2012

The DNO earth rod every, or at least every other poll in a TT area thats allowed to be converted to PME. Have a look outside to see if they have. also the joints should be crimped. If not then the area may not be suited to PME and it was done DIY. but chances are its ok, and the lil extra stake is fine..

telectrix · Mar 10, 2012

round my way there's a whole estate, biult in 70's , TN-S with earth rod as well. 6mm bonding on those i've worked at has been fine , made a couple of CU changes easy.

SPARTYKUS · Mar 10, 2012

Tn-s, nah thats a rubbish idea having a dedicated earth path back to the transformer. Much better to use the neutral

needasparks · Mar 10, 2012

TNT earthing sounds all good but get an earth fault and you better take cover.

Joking aside, I have seen DNO do a pme then taking an earth leg back to the joint they have done when cutting in, I asked about them doing it and it was to earth the armouring underground as so many joints were done inthe street it let alot of the cable unprotected.

Knobhead · Mar 10, 2012

The mind boggles ! ! ! !

Engineer54 · Mar 10, 2012

Tony said:
The mind boggles ! ! ! !

It does indeed!! Why would you want to remove this earth rod connection on a PME earthing system?? It's acting as another point of the protective multiple earthing!!! In fact it would be recommend that EVERY house or property supplied with a PME connection should have an earth rod on the property. An actual requirement in most European countries too!!!

For those that think an earth rod or mat should not be connected to a TN-S supply... It was common practice for every Council housing estate in the boom building era to do exactly that, from the early 50's to the 60's. they only stopped providing these additional earthing arrangements because of cost constraints...