Low voltage.

[raysheehan]

Hi, can anyone tell me if there is a minium supply voltage for domestic properties? My father lives in a bungalow with a TT earthing arrangement and we have noticed the lights continuly flicker, which is more noticeable on a flourscent fitting. I have measured the voltage at the incomming side of the consumer unit at as low as 225v. Any ideas please.

 

[GLENNSPARK]

whats up with 225V....

 

[micknew]

230v +- 10% = 207v - 253v.
So the supply voltage is within limits.

 

[telectrix]

225v is within limits. you may find that the voltage drops when demand is high. fluorescents will flicker below 220v.

 

[Marvo]

This kind of problem could have many different causes. Some of the possible causes are inconsequential but it could also be an indication of a more serious problem somewhere. It might be worth getting an electrician to do some basic tests and get a report for peace of mind.

 

[Deleted member 26818]

230v +- 10% = 207v - 253v.
So the supply voltage is within limits.

230v + 10%, - 6%. 216.2 v - 253v.

 

[micknew]

Sorry, I should have said +- 10% without a load.

 

[MarkieSparkie]

230v +- 10% = 207v - 253v.
So the supply voltage is within limits.

The supply industry has actually done nothing physical to reduce the nominal supply voltage from 240V to 230V, it's still 240V open circuit at the terminals of the local supply transformer. What has changed, as part of European harmonisation (Cenelec HD472), the declared nominal voltage changed from 240v +-6% (between 225.6 and 254.4V) to 230V +10% -6% (between 216.2 and 253V), very little change, just a slightly wider margin at the lower end. This suits the DNO's just fine as it gives them a bigger window of acceptable supply voltage in rural areas, without the associated costs of rewinding transformers or tap changing.
Note:- A second round of harmonisation with a change in the declared nominal supply voltage (Cenelec HD472-S2) of 230V +-10% is pending, it was due on 1/1/2008 but has yet to be implemented in the UK.

 

[langstroth2]

Sorry to revive this thread, but I have a similar issue (I'm a consumer btw, not an electrician). The last few days we've had periods of low voltage - first noticed due to the Solar Panel inverter cutting out (as it's designed to do) at 207V.

The plug in energy meter (not that accurate I know) has read as low as 203V and up to 222V (which I except although low is within tolerance range).

Any idea on what could be the causes of this?

I went next door (assume they'd be on the same phase?), they were reading 233V when our house was reading 205V.....

I have notified my DNO.

edited to add: we live in built up areas, so not rural line etc.

 

[malcolmsanford]

It could be excessive load have you bought/installed something recently that is heavy in this respect.

It could be that your the last on a phase and someone before you on this phase have done the same and bought something meaty

It could be a sign of a failing joint in your network or a loose connection, though if that was the case of being in your house you would most likely hear it.

I would not judge anything on your neighbours house to be honest you may be on a different phase to him and so there could be a problem back at the sub station just on your phase, ask anyone in the street or the house 3 doors away if they have noticed anything, chances are 3 house are spread over 3 phases.

Apart from the Inverter cutting out is there any other sign of low voltage, ie light flicker, kettle taking longer to boil. It could just be an inverter malfunction

Bottom line is that you will need to put on some sort of monitoring device that will give you some sort of decent indication, of what is really happening.

 

[langstroth2]

It could be excessive load have you bought/installed something recently that is heavy in this respect.​

No nothing new - and per day house consumption hasn't changed.

Apart from the Inverter cutting out is there any other sign of low voltage, ie light flicker, kettle taking longer to boil. It could just be an inverter malfunction​

​

Yes, slow running microwave turntable; light flicker. Plus my plug-in energy monitor is showing low voltage at various wall plugs. So I'm pretty sure inverter is OK.

I've had a call back from local DNO (who were very prompt in responding to be fair) saying they were working in the area and implied, but weren't specific, that this could be the cause.

Thanks for the info re: next door. I assumed a block of houses would all be on the same phase - but i guess there's no telling whether you are on the boundary of a block - or it's more "random" than that.

 

[HandySparks]

re: next door. I assumed a block of houses would all be on the same phase - but i guess there's no telling whether you are on the boundary of a block - or it's more "random" than that.

Unless you share a branch cable with the house next door, usually you'll be on different phases to the houses either side of you. ie Red, Yellow, Blue, Red, Yellow, Blue, etc ... down the road. (Or Brown, Black, Grey ... nowadays?)

 

[langstroth2]

Unless you share a branch cable with the house next door, usually you'll be on different phases to the houses either side of you. ie Red, Yellow, Blue, Red, Yellow, Blue, etc ... down the road. (Or Brown, Black, Grey ... nowadays?)

Thanks for that - learn something every day!

Back up to 236V this evening - so what ever they did locally today (as mentioned in my earlier post) hopefully has fixed it