Continuity and low ir

[Pondy]

Evening all,
get called to a three storey block of flats which has had water ingress into the ryefield board, basically there is three massive tanks above the riser where the ryefield boards are and one of the pumps on the tank decided to let go. The first floor has no flats, (it used to be an office and is attached to a co op.) The is a ryefield board on the second and one on the third floor, the fire brigade have come along and pulled the main fuses so the whole building is dead. I am tasked with making sure that the ryefield boards are safe to get edf to reinstate the main fuses. Each board is feeding 7 flats.
Ir on the first board between the phases and earth and neutral and all is fine, the second board I test and there is no ir (0.00) between all three phases and earth and neutral, well, I inform the powers that be, and a couple of days later I'm told its fine, I go down there and test it and it's still the same, edf come along and liven it up and all is well, it's obvious I'm missing something here, obviously there was no continuity between phases etc, so what did I do wrong??? It's a tncs system I believe,

 

[davesparks]

Did you disconnect all loads and also the incoming neutral?

 

[PEG]

Hi Pondy,who was it that you gave the results of your failed IR test,and then OK'd the reinstatement of main fuses? I know these jobs sometimes go zig-zag from standard practice,so it's no dig at you :stooge_curly:

 

[Badged01]

...... it's obvious I'm missing something here, obviously there was no continuity between phases etc, so what did I do wrong??? ....

I'm gonna guess the new school EDF "electrician" did his own checks to confirm there wasn't any faults or the old school EDF "electrician" just connect it up in the knowledge that if there was a fault it would blow and it didn't!!

And I suspect the answer to your question as to why you were finding a fault but there actually wasn't one, is as davesparks alludes to above with the way you may have been testing ......... ??

 

[Pondy]

The EDF guy was very good, spent a good while testing then put gauntlet gloves and a riot shield over his face before reinstating. The day after I had first seen it they had someone else, (head of electrical services I'd imagine ) test it and deem it fine to place back into service.all the service heads where removed. Just feel stupid for misdiagnosis and can't see who I did.
The neutral was still connected though