absent neutral

[Dm7192]

i was recently at a domestic job and just want to clarify something that happend, i carried out a periodic inspection and when i opend the single phase fuse board the main incomming neutral was lying disconected however the lights and all final circuits where functioning fine is this because the supply type is Tncs therefore the final circuits are gettin a neutral return via the earthing arrangments?any help would be appreciated

 

[tony mc]

Even on a TNCS system, im not sure how everything would still be working with the N dissed.

I was thinking through the general mass of earth now a TT system Jason!!

 

[GLENNSPARK]

I`d IR test the lot here mate.........

 

[sparkinlee]

i was recently at a domestic job and just want to clarify something that happend, i carried out a periodic inspection and when i opend the single phase fuse board the main incomming neutral was lying disconected however the lights and all final circuits where functioning fine is this because the supply type is Tncs therefore the final circuits are gettin a neutral return via the earthing arrangments?any help would be appreciated

This does sound strange! As you suggest, for everything still to be working there must be a return path somewhere, but it cannot be be a result of the TN-C-S arrangement itself as that connection is upstream of the CU.

So, as others have suggested, it seems likely that there is some connection between N & E in one of the circuits which would provide the return 'neutral' path. If there is any RCD on the board, such a fault would have to be on one of the non-protected circuits. Bearing in mind that this fault was carrying the entire return current for the whole installation it's important to find it and repair.

But then you say that all you periodic inspection readings (presumably including IR readings on all circuits) were OK... did none of the IR readings indicate some sort of fault?

(Sorry - most of this has been said earlier in some ways earlier in the thread - just trying to get my thoughts in order!)

 

[Dm7192]

Guys just to clear up this post, i recently returned to the job and managed to find the fault by disconecting the main neutral from the supply authority isolater, and with the final circuits still functioning i disconected each neutral from the neutral bar 1 at a time untill they stopped working, so by proccess of elimination i found a neutral to earth fault in the lighting circuit, which ofcourse was supplying the full house with a neurtal link to earth. You would think simple enough to find haha however after inspecting every light there was no sign of neutral earth short, therefore the only place left that the fault could be is in 1 of 2 or the adaptiable joint boxes that for some reason was installed in the house during original installation!! which was coverd in artex and needed to be asbestos tested and the other behind the consumer unit haha so needless to say a nightmare job! however thanks for any help guys hope this helps with any faults in future

 

[Dm7192]

aww and reason no fault was detected is due to a typical faulty fluke meter!!

 

[Knobhead]

It doesn’t bear thinking about, a whole house neutral via a lighting CPC. I take it there was no RCD!

 

[Deleted member 9648]

How's that not gone up in flames??......oh,and thanks for the update on the problem,so many times on here the outcome of the outcome remains a mystery.

 

[tony mc]

Thanks for the update I bet you are a lot happier now finding the fault as thats what a PIR is all about.

How many none RCD protected installations are out their with a Neutral Earth fault which is a very dangerous situation.

 

[ipf]

Still can't understand why the neutral wasn,t connected. Suspect some idiot somewhere knows something.

 

[mickys86]

Still can't understand why the neutral wasn,t connected. Suspect some idiot somewhere knows something.

There's an idiot out there but I don't think he knows anything. Haha