Ze reading on TNC-S system

[avinalarf]

Evening all

Measured the above today and am getting 0.4 reading. I know this type of system should have 0.35 max so what could be causing it to be higher?

Should I be very concerned and what steps should I take?

Thank you.

 

[Lurch]

Only steps you can take really is contact the DNO. If they can get it back to <.35 then great, if not stick a rod in.

 

[Bez]

As above, phone call to DNO

 

[batty]

Probably your meter is not that accurate. What do you have? The most accurate ones seem to be the ones that send 25 amps down the cables. I have an old robin with d-lok usually if you test with this the readings are a bit lower than with my fluke 1652.

Batty

 

[Andy™]

may be a long distance from substation. you will need to contact DNO to get it sorted

 

[avinalarf]

Probably your meter is not that accurate. What do you have? The most accurate ones seem to be the ones that send 25 amps down the cables. I have an old robin with d-lok usually if you test with this the readings are a bit lower than with my fluke 1652.Batty

Hi Bats

I've got a Fluke 1652, which I check monthly with my calcard and readings have been ok.

Will contact DNO tomorrow.

Cheers to all.

 

[Lurch]

I've got a Fluke 1652, which I check monthly with my calcard and readings have been ok.

I think what he's getting at is that the Megger might not be accurate in general, not that it is wandering over time.

I'd still get the DNO on it anyway, bit close anyway so could be an early indicator of a fault elsewhere.

 

[tom1]

Only steps you can take really is contact the DNO. If they can get it back to <.35 then great, if not stick a rod in.

just thinking but if you rcd everything like a tt would you need a rod?

 

[Lurch]

just thinking but if you rcd everything like a tt would you need a rod?

Still doesn't change the fact that the Ze is .4 on a TN-C-S.

 

[tom1]

Still doesn't change the fact that the Ze is .4 on a TN-C-S.

true,

 

[batty]

Hi BatsI've got a Fluke 1652, which I check monthly with my calcard and readings have been ok.

Will contact DNO tomorrow.

Cheers to all.

calcard will not check your loop though.

 

[Voltimax]

DNO probably won't worry about it being that close. I had a similar problem about 4 years ago, the reading was 0.65. They sent engineer out and he said the cable run was obviously too long and had been that way for years, nothing was done about it. No need for rod, so long as your Zs readings on your circuits comply all is OK, not saying you shouldn't get DNO out though as there may be a problem that will only get worse and make sure they put it in writing if they say it's OK and do nothing. Always best to cover ones rear end!