Dimming lights

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I have an issue with my electrics which only appears to show itself as occasional dimming lights.
I have proved that the problem is not on the lighting circuits as you notice it also on a table lamp connected to the ring main.
The problem is not constant nor can it be identified to any particular time of the day.
I have noticed it happening at 07:00 when no-one else is up and the only apparatus running is a freezer, fridge and CH. Last night it was more noticeable for a minute or two and the HW pump would not have been on and therefor only fridge and freezer would have been on.
The problem is only noticeable on lighting and I assume modern electronics handle the variances without showing them.
A friend had a quick look at consumer unit at the weekend (he is a spark) and said all the feeds from and the supply to it appeared OK.
Can anyone please throw any light on what may be the problem as my wife is now panicking - perhaps I should too. Many thanks.
 
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If nothing is switching in your house then most probably the incoming supply voltage is dropping. Another user nearby is turning on a large load and this is causing the voltage in the area to drop. A factory starting up in the morning is one common cause. Off peak load switching is another

If it is a serious problem then contact the DNO for your area and tell them.

http://www2.nationalgrid.com/uk/Our-company/electricity/Distribution-Network-Operator-Companies/

They can and should carry out voltage monitoring to determine the reason.
 
A friend had a quick look at consumer unit at the weekend (he is a spark) and said all the feeds from and the supply to it appeared OK.
Appeared to be.

Did he do any tests?


Can anyone please throw any light on what may be the problem as my wife is now panicking - perhaps I should too. Many thanks.
Panicking is perhaps an overreaction, but you should be concerned - if you have a poor connection somewhere it could overheat.
 
I have to confess that I only asked him to check the screws on the feeds as I was worried that the problem may be loose screws.
Today I removed all the fuses barring the aux. one which also powers an incandescent bulb under the stairs where the consumer unit is. That light still flickered and I therefore concluded (rightly or wrongly) that the fault was not on the distribution side.
I am not on speaking terms with one of my neighbours and the other says she has not noticed flickering herself although she may not use incandescent bulbs.
From what I can gather, before the Board will come out I will have to have a spark measure the voltage for consistency.
Is this info right, what more can I do as this needs resolving. Thanks.
 
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Have you noticed the supply fuse getting warm in use, particularly when you've got a large load on?
 
Your next doors neighbours may not experience the same problem as you. They may be on a different phase, depending how your street is wired up. There are 3 phases, the problem may only be on one of them and manifest itself in every 3 houses. But sometimes houses are wired in banks of 4-5 on one phase.
 
before the Board will come out I will have to have a spark measure the voltage for consistency.
Is this info right, what more can I do as this needs resolving. Thanks.

Well, you could measure the voltage for consistency couldn't you?
 
before the Board will come out I will have to have a spark measure the voltage for consistency.
Is this info right, what more can I do as this needs resolving. Thanks.

Well, you could measure the voltage for consistency couldn't you?

I measured it at 247/248 when it is OK. But when it's flickering the voltage fluctuates between 238 - 249v. As I type it is OK but I am hoping to monitor it during the day and write down bad times. Last night at 23:00 it was particularly bad and I have had a spark check the CU again and all is tight and the main fuse isn't getting ward and no spurious sounds or smells in the vicinity of it.
As I said, I cannot ask one of my neighbours but hope to talk to the other side tonight but they have only ben there a few weeks. I thought that maybe their arrival coincided with the introduction of the problem but I'm sure that the flickering started before that although it is a lot worse now.
The spark suggested that the fluctuating voltage although a nuisance would not be dangerous. He suggested tolerating it for a while to see if it corrected itself and he also suggested "dirty electric" supply and odd harmonics.
 
I did have a period when my RCD was tripping around twice a month which also caused the lights to flicker before it tripped and I was considering swapping to RBCO's to try and cure the problem. Then the electric board dug up the road up the street and faults stopped without me doing anything.

So yes these things can seem to cure themselves but really I am sure it was down to a fault in the street. I am sure if you phone the DNO and complain they will log it and if others in the street do the same they will take action so I would phone.

Some DNO's do not permit the use of welding sets and the like on a domestic supply I am told but I have been unable to confirm this. The use of a welding set could cause what you describe.
 
Your house will be supplied by one of three phases in the street cable. It is likely your next door neighbours will NOT be on the same phase. The neighbours two doors away are the most likely to be on the same phase as you.

That is generally the case but not always.
 
Your house will be supplied by one of three phases in the street cable. It is likely your next door neighbours will NOT be on the same phase. The neighbours two doors away are the most likely to be on the same phase as you.

That is generally the case but not always.

That was certainly the case. She beckoned me this morning to confirm that she did indeed have the problem. Armed with this knowledge, I contacted the DNO (thank you Bernard for the URL) and they were on the case within 2 hours.
The guy found the fuse arcing at the sub-station, and when reseated, rectified the problem.
Thumbs up to those at UK Power Networks and many thanks too to all posters offering advice/info.

PS. Out of curiosity. Why if there are three phases, would my neighbour next door but one be affected too.
 
PS. Out of curiosity. Why if there are three phases, would my neighbour next door but one be affected too.
The three phases all share the same neutral back to the sub-station. To have the "correct" voltage supplied to the house the Neutral needs to be at zero volts. If the load on each phase is the same as the other two then no current flows in the Neutral and there is no voltage on the Neutral at the house.

But if the loads are not equal there is current flow in the Neutral and the Neutral at houses is not zero. In some houses this voltage causes an increase in the supply voltage and in others it causes a reduction. Your next door but one neighbours supply will be affected by the varying voltage on the Neutral even if the voltage on her phase is "correct".
 
She might be on the same phase as you. Whilst every third house on the same phase is the ideal situation, in the real world it's not going to happen all the time.
 

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