High Earth Fault Loop Imedance

[securespark]

For your information, fireman, this tester does Auto RCD test, resistance, IR, RCD test RCD soft test, Individual RCD tests, ramp tests, to name but a few....

 

[dazzo74]

Hi securespark & Adam......
O.k just redone the test and yes i disconnected the main earth wire and connected my earth lead from my tester via a croc clip, with black probe on live and blue on neutral (with isolator in off posistion),

Set dial to LOOP L-E and pressed start to show my Ze of now 5.87 ohms
Pressed dislpay to get my PEFC of 41.4 Amps

Turned dial to LOOP L-N and pressed display,got a reading of 0.25 ohms which i ignore but...
Pressed display and my PSCC reading of 968 Amps was shown.

Meaning i have a Ze of 5.87 ohms and a
PFC of 968 Amps.

 

[plugwash]

well either its NOT TN-C-S or there is a serious fault somewhere.

on a TN-C-S earth loop impedance should be extremely close to netural loop impedance (any differences should be down in the single digit miliohms assuming your main earth isn't hugely long).

if you can disconnect it without breaking any seals i'd try replacing the main earth cable from the cutout. If its still bad then either your tester is faulty or its the suppliers problem.

 

[securespark]

I would present your findings to the DNO if you have TN-S or PME. If you have TT that is an OK reading but as I said before, you MUST have an RCD on a TT supply to give you protection against the high reading.

Did you look into whether or not you have a TT system??

 

[dazzo74]

Right sorted ............
Many thanks to all that replied ,im going to get some pics up of this to show but...........
Got the DNO out and when he looked at my system he laughed his noggin off because at some point (and it must have been the original distributer)
they had used a TN-C-S service head but i didnt have the TN-C-S supply.
I have,like was pointed out to me by you lot ,a T.T system.
The earthing wire would have originally been connected to my incoming water pipe and that was,in the 30`s (when my house was built), the accepted method of earthing.

The engineer that came out has ordered a new service head but has told me they are not expected to supply me my earth so i've just had a trip to screwfix and now invested in an earth electrode and a new consumer unit with a 100mA main isolator split to a 30mA for downstairs ring circuit.

Thanks again for all your help guy`s,pats on the backs for all of you.

 

[plugwash]

remember to test the rod alone with your EFLI tester after installing it. Its not unheared of to drive a rod into material that turns out to be totally noncondutive.

 

[securespark]

Two points:

Make sure your Zs does not exceed 200 Ohms.

As mentioned before, make sure also that your board has an S type RCD (Time Delay) 100mA minimum for the incomer and a 30mA on the split side.

PS

Daz, I'm in Stockport. Which bit of Manchester has a TT supply?????

 

[Adam_151]

Two points:
Daz, I'm in Stockport. Which bit of Manchester has a TT supply?????

Any part of it, when the DNO CBA to give you anything else, it seems...

 

[JohnD]

.... an S type RCD (Time Delay) 100mA ...

They're not cheap, are they?

 

[dazzo74]

Small world securespark......
Im stockport too mate..Offerton to be exact.
Im just off turncroft lane apparently in a part the used to be Woodbank Park,so im told.

Thanks for the additional info fella`s ,Ill print this off and get it sorted A.S.A.P.