Voltage between Cpc and neutral

[linsaband]

Hi

If anyone can help,I am carrying out an EICR on part of large hospital and have found voltage that varies between 100 and 200v between live and neutral on one single phase submain cu. It is present when main switch is off so is on load side. Apparently they get voltage around 0v to 60v sometimes due to machines connected on a particular circuit but I have isolated what i can and still getting this voltage. Any ideas, cheers

 

[Engineer54]

First of all, ....try using an analogue voltmeter, instead of a DMM or other digital jobby!!

 

[sledgehammer]

Forgive my ignorance but this is the 2nd time you (I think) have said use an analogue meter, whys that? And can you even buy one readily as I've not seen one in years.

 

[Silly Sausage]

Have a read of this...
Find_It

 

[pete.willerton]

I've had this on a section board and it was a loose busbar link on the neutral giving all kinds of incorrect voltages !

 

[linsaband]

Have a read of this...
Find_It

Very interesting, will try tomorrow when on site

thanks

 

[Marvo]

Firstly be aware the hospitals may in certain areas utilise IT earth arrangement. Have you established for sure what earthing arrangement you're dealing with?

Forgive my ignorance but this is the 2nd time you (I think) have said use an analogue meter, whys that? And can you even buy one readily as I've not seen one in years.

Analogue tester are not fashionable but they're available from all major suppliers. Every electrician should have one. They have a lower input impedance so they don't give confusing readings where capacitively coupled or induced voltages may be present.

 

[Paultrim123321]

I've had this from emergency lighting and some UPS systems over the years.

 

[sledgehammer]

Cheers Marvo, I'm reading.