Earthing Problems

[mtt.tr]

Well that's me flummoxed!

With my old meter, uncalibrated I get a consistent 21 ohms (11A to earth give or take). Tbh I thought that pretty good. The max I think for a TT in the OSG iirc is 20 + 1 "for the rod"?

I then tested using work's new MFT, calibrated etc. Got a well low reading:

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Trouble is it's not repeatable, all over the shop on successive tests:

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Loose connection maybe? Think I've some dead test results for that ring somewhere...

This happens with meggas if the leads are left in and layed down they become loose at the PCb

 

[Onoff]

This happens with meggas if the leads are left in and layed down they become loose at the PCb

Leads weren't left in. Tbh the meter on the left has hardly been used since new. Leads lying loose in the box.

 

[Onoff]

This is interesting:

Never the same loop impedance twice

A common complaint about earth loop impedance testing is that if several tests are carried out on the same circuit, it often happens that each test gives a different result. Why is this and what can be done about it? Simon Wood of Megger has the answers.

www.voltimum.co.uk

 

[Guineafowl]

The no-trip loop test is a bit variable, due to the widdly little currents involved, noise etc.

 

[dobbslc]

Are you plugged into the ring or is that from the rod ?

 

[dobbslc]

Is the Megger set to 2Lo or 3Lo?
I find 2Lo is often very variable especially on TT earthing systems!

 

[Onoff]

Is the Megger set to 2Lo or 3Lo?
I find 2Lo is often very variable especially on TT earthing systems!

Plugged into the ring. Set to 3Lo.

 

[dobbslc]

Mmm, the 3Lo setting is usually pretty steady, I get poor readings sometimes if the socket terminals are tarnished or knackered, try taking the socket off the wall and using the probs.