Main Earthing Clamps

Ladders · Nov 30, 2011

Hi. Once again I go to a property and find the 16mm earth to the TNS system head is on a standard 'sparky' earth clamp.
Problem is. The client wants me to change all the fittings to metal ones. So as the main earth is not correct I presume I can't? Will the client have to pay the board to fit the correct type of clamp first before any work takes place?
No sign of the orginal earth strap anywhere plus the installation does not comply like this anyway!

mechelec · Nov 30, 2011

Yes the client will have to apply and pay for PME if it is available, or you install an earth rod and run it as a TT system

topquark · Nov 30, 2011

I'd first try to contact the DNO for the area and see if they will maintain (ie fix) the existing TNS system, that would be free. To install TNCS(PME) would most likely cost the home owner of the order of £150.

goldie · Nov 30, 2011

Would the supplier be responsible for the main earthing? Could they keep it on a tn-s and put their own clamp on mechelec?

Ladders · Nov 30, 2011

topquark said:
I'd first try to contact the DNO for the area and see if they will maintain (ie fix) the existing TNS system, that would be free. To install TNCS(PME) would most likely cost the home owner of the order of £150.

Interesting. Ask the DNO for a 'repair' first. Worth a try! Cheers.

Ladders · Nov 30, 2011

mechelec said:
Yes the client will have to apply and pay for PME if it is available, or you install an earth rod and run it as a TT system

Cheers. Had one last week like that. Took them 8 weeks to get to the job!

telectrix · Nov 30, 2011

that quick?

Engineer54 · Nov 30, 2011

So what's the Ze on this cable sheath?? If it's under 0.8 ohm then it's most definitly a TN-S supply. If that's the case, why not just replace this standard clamp, with a couple of constant tension spring clamps and appropriate braid tail?? I certainly would!!

Knobhead · Dec 1, 2011

As E54 said use a constant pressure spring and copper braid. Before you put the braid on give the lead sheath a gentle rub with emery to get bright metal, (and I do mean gentle).
http://solutions.3m.co.uk/wps/portal/3M/en_GB/ElectricalMkts/ElectricalSupplies/ProductInfo/ECatalogue/ElectricalEarthing/ConstForceSprings/

mechelec · Dec 1, 2011

goldie said:
Would the supplier be responsible for the main earthing? Could they keep it on a tn-s and put their own clamp on mechelec?

It sounds in your case that there was no earth supplied to the property. If they had supplied an earth it wuld have been either a hepbond (braid clamped to lead) fitted or a simple copper wrap (several turns of single uninsulated copper wrapped around the lead) usually under pitch impregnated cloth tape. If the above is correct then they would charge the same for either PME or TNS earth terminal as effectively the main job is providing a hepbond to the cable and a henly block. The only difference is a link between neutral and earth terminal (PME).
That said if the cutout was damaged then they would come out and repair within 4 hours and if available PME it at the same time.