Earthing and voltage issues

[daiplayer]

Hi all

Having a strange problem with some testing .

Did an installation for somebody and upon testing discovered high Ze . ( 640 ohm )

Not happy with result ( after testing all other earthing conductors to infinite ohm or higher than 640, bonding no doubt), i discovered the earthing conductor was not connected to an earth rod, neither is there a rod to be found.
ok....so replace earth rod and conductor .

However im also getting some funny voltages accross the board. I did some ir testing to see why it is that somebody has discconected the earth ( possible earth fault ) , all good other than one mcb . Mcb of course was off ( as were all the other plus the main switch) however i was picking up flucuating voltages between the L ( at the top of the breaker which was off ) and earth of 105v , 50v, 96v , 12v, and kept on fluctuating .

The supply voltage seems fine L-N , 230Vac.

I cant understand why there could be voltages appearing on the earth or the live to the breaker when the dp main switch, rcd , all mcbs, were off ? any ideas ?

 

[RyanCheetham]

Bad batteries in your tester?

 

[daiplayer]

thats what im wondering , dodgy tester ? :-/ , however it only seems to do it on this one single circuit. . could dodgy batteries do that then ?

 

[telectrix]

try using an analogue voltmeter/multimeter. and what's the Ze now you have reinstated the earthing?

 

[RyanCheetham]

It can if its digital, as Tel has suggested try an analogue tester

 

[daiplayer]

i havent done the earth rod yet . the house is unoccupied at the moment so ive left it all off. ( was 8pm last night )

 

[RmBo_0]

Yeah if there is a broken earth then your digital meter will pick voltages up like that. Think it's called capacitive coupling.

 

[Silly Sausage]

try using an analogue voltmeter/multimeter. and what's the Ze now you have reinstated the earthing?

Or, put a 230V lamp in parallel with your Digital meter.

 

[daiplayer]

Yeah if there is a broken earth then your digital meter will pick voltages up like that. Think it's called capacitive coupling.

Well thats a new one on me .... as they say , learn something new everyday.

- - - Updated - - -

Or, put a 230V lamp in parallel with your Digital meter.

i did that yeah. i did it with the multifunction, then with my fluke voltage indicator , and it showed the same.

 

[daiplayer]

ok further note..... wandering around the board with my voltage indicator, testing everywhere for funny voltages.

Tested between the incoming N, ( top of dp switch) and the m.e.t. .......and shows continuity.....

why would this happen ???
and before people scream TNCS ! , i did a loop test L,N, and the m.e.t. to rule this out. and shows 343 ohm. im guessing two parallel bonding conductors through the pipework .