400V between L&N

[tony mc]

I dont know what limitations you have agreed and you say you have isolated the CU in the shed.

I would be looking at what feeds the CU and you will most likely find as Tel has said it has been wired wrong and is fed by 2 phases.

Its then down to you what codes you issue and if a code 1 I would be issueing a dangerous notice to the person ordering the EICR.

 

[Ago4Ago]

I dont know what limitations you have agreed and you say you have isolated the CU in the shed.

I would be looking at what feeds the CU and you will most likely find as Tel has said it has been wired wrong and is fed by 2 phases.

Its then down to you what codes you issue and if a code 1 I would be issueing a dangerous notice to the person ordering the EICR.

Agreed, problem is; disboard feeding CU in shed has been boxed in making it impossible to take the front off. So for now I have switched the 3 phase mcb feeding it off. The thing is. The circuit to the shed and the circuits from the CU in the shed look like they have been there some time, so I cannot see that there has always been 400v between L&N. I have logged it as a C1 also requiring further investigation.
It is just puzzling me as to how it has come about. Hence; throwing it in here in case anyone has any similar experiences.

 

[telectrix]

well, if the DB has been made inaccessible by boxing in, ytou need one of these builders' precision tools. make sure it's in calibration.

 

[Darkwood]

If you are testing throughout the factory it could be the case that a Neutral has been left disconnected and a floating neutral created between phases which can rise the voltage in excess of 400v on a single phase load, you can easily check the origin of the circuit to see if it is truely been tagged as a bodgit 2ph or is in fact connected as 1ph.... if the latter then a floating neutral is a highly likely situe and fingers crossed you aint blown any connected single phase loads throughout the factory.
A faulty 4pole switch contact on the neutral can cause this but im sure you have followed protocol and had all outgoing circuits isolated before switching back on and voltage check before re-energising.

 

[Ago4Ago]

If you are testing throughout the factory it could be the case that a Neutral has been left disconnected and a floating neutral created between phases which can rise the voltage in excess of 400v on a single phase load, you can easily check the origin of the circuit to see if it is truely been tagged as a bodgit 2ph or is in fact connected as 1ph.... if the latter then a floating neutral is a highly likely situe and fingers crossed you aint blown any connected single phase loads throughout the factory.
A faulty 4pole switch contact on the neutral can cause this but im sure you have followed protocol and had all outgoing circuits isolated before switching back on and voltage check before re-energising.

Thanks Darkwood. I would like to discus further with you but your private message seems to be full.

 

[guest119]

Lost neutral.
Seen it before, 380v at a 13a skt.
What is suposed to be the neutral is returning through the other phases, like an unearthed star point.

Boydy

 

[telectrix]

forgot to mention the calibration procedure for sledgehammers.

1. hit a plumber over the head with the hammer under test.

2. accurately measure, with a stopwatch, how long it takes from the impact with the hammer to the impact with the ground.

3. anything under 5 seconds, the hammer passed calibration.

4. if the installation is TT, however, you need to hit him twice. TW*T, TW*T.

 

[Darkwood]

http://www.electriciansforums.net/e...egulations/69309-suppliers-neutral-break.html

here's the link to another thread that gives a better understanding of floating neutrals... Sintra's posted diagrams explain it very well.

 

[bigbaddave]

Thanks Darkwood. I would like to discus further with you but your private message seems to be full.

I am sure you can access his box for a fee

 

[Darkwood]

I am sure you can access his box for a fee

Hey i dont swing that way .... thank you very much

 

[shagbite]

if you did, the o.p. would end up with dark wood. (sorry!)

 

[Ago4Ago]

Bingo! Dismantled half a staircase to gain access to Dis-Board feeding Consumer unit in question & sure enough a burnt out neutral. Not originally tightened enough by the looks of it.

 

[Darkwood]

Glad you found it .... bill as extra emergency repair keep any evidence or take pictures, be cautious of the damage the heat has caused if like where it was clamped if major discoloration has occured it best to replace the busbar or terminal bar when you get the chance as the heat will have altered the metal and it can become a weak point and re-occur.

 

[Nivag316]

Check to see if the neutral has gone high resistance.

 

[Nivag316]

Sorry only got half way cown the post before posting the previous