testing at 400v domestic lighting in 2 too

[kels bels]

Hi there
I was called out to a job this week where clients bulbs are blowing frequently. I expected to test voltage for the property and see a high voltage around 245/250...
However when I arrived the client told me a previous electrician, who I spoke to on the phone whilst I was there, had measured voltage at the switch for kitchen/living area at 380-400V.
He therefore disconnected the lights as they were just blowing straight away.

I told customer that I couldn't reconnect these lights as it would be dangerous. Electrician also said that sometimes there was power coming to the switch and other times it was dead. He said that he thought there may be a crossover between the flat above and this one ie. kitchen lights supplied by both a circuit from this flat and one from flat above.

I'm going back when the neighbour from the flat above is home so I can isolate her power and see if that affects my clients lights - has anyone ever come across anything like this before? And any thoughts why there would be 400v at lights in one particular room and not throughout the whole house?

I was getting 245v through rest of the flat.

Thanks! Kelly

 

[davesparks]

As usual we need more information.

When you tested the kitchen switch,
What was the 400V measured between?
Was everything at 230V to earth?

If the single phase voltage is 245 you would normally expect phase - phase voltage to be over 415, being as low as 380V is a bit odd.

 

[Engineer54]

So why can't you isolate the flat you're working in, and test/trace for any voltages that are present??

Are these purpose made flats or is it a house (or whatever) converted into flats??

 

[GMES]

As above ^^ Eng54
Isolatote mains coming in and test for any voltage, if voltage is present at the switch then it is being fed from flat above!!

 

[Darkwood]

Does the building have 3phase to it...Flats on different phases?

Has anyone been doing stuff with either the lighting in the flat above or below, this other electrician he said he had ...curious why he was there and didn't sort it out!... some Electrician urh!!

I suspect the previous so called sparks has mixed the lighting in this flat with the lighting of the other flat maybe where they run together through ceiling/floorboards adjoining.

What was the other Electrician there for and did you ask why he hadn't sorted it?

 

[Marvo]

If the building has 3-phase and your flat is fed by one of these phases then there could be a floating neutral. If it is floating it will assume a voltage approaching that of the heaviest loaded phase so you could test anything from 0 to 400 volts L-N depending on the overall building load characteristics. Be especially sure to make all your safe isolation tests because if you only test L-N it could catch you out.

 

[Darkwood]

I thought that way too but as this is only affecting lighting and seems to be localised then went for my suggestion as all the Electronic devices would have blown too...

 

[Marvo]

Ahh, doh, sorry I missed the last line where he says ha got 245v in the rest of the flat. Depending on how he was testing the 400v at the lights and 245 v elsewhere it probably rules my theory out.

 

[robsparky1975]

Sounds a bit dodgy,who knows what someone may have done,does the tenant know of any work that has been carried out recently in downstairs or upstairs flats? suspect anything and trust nothing would be my advice.Isolate downstairs and dead test(prove dead aswell) IR,continuity test etc,check to see if circuit is healthy,check supply voltage etc.

 

[Knobhead]

Hi there
I was called out to a job this week where clients bulbs are blowing frequently. I expected to test voltage for the property and see a high voltage around 245/250...
However when I arrived the client told me a previous electrician, who I spoke to on the phone whilst I was there, had measured voltage at the switch for kitchen/living area at 380-400V.
He therefore disconnected the lights as they were just blowing straight away.

I told customer that I couldn't reconnect these lights as it would be dangerous. Electrician also said that sometimes there was power coming to the switch and other times it was dead. He said that he thought there may be a crossover between the flat above and this one ie. kitchen lights supplied by both a circuit from this flat and one from flat above.

I'm going back when the neighbour from the flat above is home so I can isolate her power and see if that affects my clients lights - has anyone ever come across anything like this before? And any thoughts why there would be 400v at lights in one particular room and not throughout the whole house?

I was getting 245v through rest of the flat.

Thanks! Kelly

What voltage did you get on that circuit? Please don't tell me you didn't check for yourself.

 

[Engineer54]

Looks to be, yet another case of the disappearing OP!! Were all talking to ourselves again...lol!!

 

[GMES]

Looks to be, yet another case of the disappearing OP!! Were all talking to ourselves again...lol!!

Bugger him then, How are you this morning Sir

 

[tooleystreet]

Thanks for adding me to the forum...female member here mostly to read the comments..