Voltage Fluctuating between 170V and 330V

[Izak555]

Hi,

I`ve been to a site today and noticed some units I`ve got have huge voltage drops. Voltage was fluctuating between 170V and 280V and on some units, I`ve had 330V.
I went to the DB board:

• Between live and earth some circuits were showing 217V and other one were showing 270V.
• Between Neutral and Earth, some circuits were showing 60V. When isolating each all MCBs, I`ve had 240v between neutral and Earth.
• The main supply was ok.

It looks like the issues is on the floor and feedback this on the DB board.

There are about 15 circuits. Each of them is connected to two spurs and feeding some VAVs boxes.

What could be the reason of the voltage fluctuating like this?

Many thanks,

 

[James]

Faulty neutral is the obvious suspect.

why do you think that the supply is ok?

 

[snowhead]

As James, it's a Neutral issue, poor or dis connection, either at the 3 phase DB or at the source to that D.B

 

[Mikegh]

As above you would think

Not the sort of issue you want to be leaving unresolved

 

[Izak555]

Yes, it needs to be resolved as some of the transformers burnt and we had some fire in some boxes.

Can the issue with the neutral comes from the floor of the DB board itself? I mean can the neutral disconnected be found on one of the spurs?

 

[Mikegh]

It's the type of situation where you switch off immediately to prevent expensive equipment damage

Until a solution is found

 

[Izak555]

Thank you all for your prompt reply.

 

[Lucien Nunes]

I mean can the neutral disconnected be found on one of the spurs?

No. It will be on the 3-phase supply before the first point at which abnormal voltages are found.

 

[stevethesparks]

I mean can the neutral disconnected be found on one of the spurs?

I am amazed at that assumption as a possible cause.

 

[snowhead]

VAVs boxes

If the O.P was only onsite for HVAC then I suggest the voltage issue is reported to whoever is responsible for electrical distribution within the building, URGENTLY.

 

[freddo]

If the O.P was only onsite for HVAC then I suggest the voltage issue is reported to whoever is responsible for electrical distribution within what's left of the building, URGENTLY.

Corrected that for you.

some of the transformers burnt and we had some fire in some boxes.

You make it sound like this is a normal everyday type of problem!

Turn the power off!

 

[UNG]

Not quite understanding why you would spend time identifying voltage issues and then ................
Post on a forum to ask for a reason as to why the voltage was fluctuating

It brings to mind Nero fiddling while Rome burned

 

[DPG]

I don't reckon he'll be back personally.

 

[nicebutdim]

I don't reckon he'll be back personally.

Perhaps they'll send an emissary to update us ?

 

[Simon47]

Agreed with the above - if you find a situation like that, you report it to the responsible person immediately. It's not a "get a brew and write a letter" sort of immediate, it's a find them in person or pick up the phone immediate. The mention of "some of the transformers burnt and we had some fire in some boxes" should be enough of a clue that it's both serious and urgent - threat of fire and threat to life serious.

 

[UKMeterman]

It is the kind of problem where you turn the supply off, and don't even think of turning back on unless the fault is fixed or you have had a blunt chat with the site MD .

 

[Izak555]

No. It will be on the 3-phase supply before the first point at which abnormal voltages are found.

That`s right

 

[Izak555]

It is the kind of problem where you turn the supply off, and don't even think of turning back on unless the fault is fixed or you have had a blunt chat with the site MD .

Well, this is exactly what I`ve done.

 

[Izak555]

There was a loose neutral cable in the DB board. It did cost a lot of money to sort it out but the electrical company found it. thanks for your replies

 

[Petej999]

Faulty neutral is the obvious suspect.

why do you think that the supply is ok?

OP what are you measuring the voltage with?

 

[timhoward]

There was a loose neutral cable in the DB board. It did cost a lot of money to sort it out but the electrical company found it. thanks for your replies

Thanks for letting us know the outcome. Glad it's sorted.