High Earth Loop Impedance

SteveF1 · Apr 6, 2009

Dear All
A mate of mine recently asked me to look at his installation. It has been wired to the 17th edition and all looks kosher, but when I carried out some testing I discovered that it had High impedance values. I disconnected the Main earth that had been connected to an earth clamp, attached to the armouring of the Supply Authority cable (old type armoured covered in hessian and bitumen). Took a reading from this clamp, this gave me a reading of 4.29 ohms taken with a Fluke 1653. The type of supply is TNS.
My questions are these:
1. Is it the responsibility of the Customer or the Supply authority to provide an Earth?
2. Is there a charge for the customer if they request a TNC-S supply (PME) instead of a TNS, seeing there is no Earth provided.

Kind Regards

Steve F

Mr Mark Sparks · Apr 6, 2009

i had a broken tn-s supply giving a high eli, reported it as dangerous and the elec board came out and did a repair at no cost,a cable tv contractor had damadged the sheath in the road.

SteveF1 · Apr 7, 2009

Thanks for your reply. The supply authority attended the property in question to-day. They said that the cable sheath was not and has never been connected to earth and that an electrode will have to be installed. I find this extremely hard to believe as this would mean that the property which was built in the 50's has never had an earth and has always been a TT system. I think I will have a look at his neighbours house.

Is there a certain distance the Earth Electrode has to be away from the property?

Spudnik · Apr 7, 2009

Normally somewhere sensible just outside the location of the CU.

Sounds to me like the property was earthed through the incoming gas and/or water service pipes.

Not ideal!!!

SteveF1 · Apr 7, 2009

Yes your probably right!
When you say just outside the location of the CU, do you mean outside the property as the CU is under the stairs.

Regards

Steve F

Mr Mark Sparks · Apr 8, 2009

yes it needs to be outside the house just find the most convenient route out and run that way, it doesnt need to be the shortest way, i would put the stake in an earth pit of some sort to protect the connection.