Lights Flickering

[Grant1987]

Hi all,

I’m having bit of a problem diagnosing a fault it’s already in my top 5 of hardest faults to find.
I’ll try to simplify lights on one circuit and also lamps plugged into sockets on the ring main sometimes flicker indicating it’s not just lighting circuit. My first hunch is loose connection in consumer unit rcd. Split load dual rcd however sockets and lights are on separate rcds. Next hunch the main switch is at fault however connections are tight and secure. It’s a terraced house with overhead supply apparently neighbours do not have same issue so can rule out loose connection on supply side HELP!!!

 

[timhoward]

I'd be checking all connections in CU including bus bars, and neutral link wires first. Also N conductors for those two circuits.
Can you try moving the lamp to another circuit (e.g. cooker switch socket) and see if fault moves?
Have you checked supply voltage?
When did it start happening? Anything changed, e.g. have they just had a smart meter fitted?
How often does it happen, how long do you have to stand there to see it?

 

[Grant1987]

I'd be checking all connections in CU including bus bars, and neutral link wires first. Also N conductors for those two circuits.
Can you try moving the lamp to another circuit (e.g. cooker switch socket) and see if fault moves?
Have you checked supply voltage?
When did it start happening? Anything changed, e.g. have they just had a smart meter fitted?
How often does it happen, how long do you have to stand there to see it?

I’ve disconnected and reconnected everything in the consumer unit, I’ve checked the supply voltage whilst there reading 234v I didn’t believe the customer at first but I asked them to record the flickering which they did and the lights do flicker I’ve supplied them with LED lamps (bulbs) but it still does it. It’s all circuits (down ring)(up ring) have not tried the cooker circuit but I know it’s going to be same outcome, smart meter was installed few years ago so can’t blame that. I stay there for about 20 mins each time looking like a fool. Checked every single connection on lighting circuits. I’ve probably found over a 100 faults during past 16 years and I’m struggling in this one. Really annoying me I’m even sleeping on the settee because I’m so restless my mild ocd is bugging me

 

[timhoward]

It would bug me too!
Trying to identify if it's truly random, or is more likely at certain times of day might provide clues.
e.g. every time someone connected to same phase takes a shower, or their hot tub stat kicks in etc.

Is there any general rule to how long each episode lasts, and do they settle again fairly quickly or go on flickering for a long time?

 

[Mikegh]

I'd try switching on a heavy load like cooker rings and see what's flickering

Usually means it's at the dB or further upstream

I'd be checking voltage drop under load too at outlets see is it dropping at the supply or board

 

[Grant1987]

I’ve disconnected and reconnected everything in the consumer unit, I’ve checked the supply voltage whilst there reading 234v I didn’t believe the customer at first but I asked them to record the flickering which they did and the lights do flicker I’ve supplied them with LED lamps (bulbs) but it still does it. It’s all circuits (down ring)(up ring) have not tried the cooker circuit but I know it’s going to be same outcome, smart meter was installed few years ago so can’t blame that. I stay there for about 20 mins each time looking like a fool. Checked every single connection on lighting circuits. I’ve probably found over a 100 faults during past 16 years and I’m struggling in this one. Really annoying me I’m even sleeping on the settee because I’m so restless my mild ocd is bugging me

I'd try switching on a heavy load like cooker rings and see what's flickering

Usually means it's at the dB or further upstream

I'd be checking voltage drop under load too at outlets see is it dropping at the supply or board

I’ve asked the same questions is it when you’re subjecting power whilst shower is on answer no it’s mixer shower. Then my next question “is it when you’re cooking” answer no it only happens every now and then and not whilst we are cooking baffling me

 

[Grant1987]

It would bug me too!
Trying to identify if it's truly random, or is more likely at certain times of day might provide clues.
e.g. every time someone connected to same phase takes a shower, or their hot tub stat kicks in etc.

Is there any general rule to how long each episode lasts, and do they settle again fairly quickly or go on flickering for a long time?

Only flicker for a short time

 

[Mikegh]

I’ve asked the same questions is it when you’re subjecting power whilst shower is on answer no it’s mixer shower. Then my next question “is it when you’re cooking” answer no it only happens every now and then and not whilst we are cooking baffling me

I'd be checking myself anyway

Incandescent is the easiest to see it with

Is it dimming or actual flickering,

The dimming usually indicates the voltage drop

The flickering I'm not sure , maybe that could be indicating an external event altogether

Someone else wiser than me will probably be along with the right answer as usual

 

[Grant1987]

Only flicker for a short time

I’ve spoken to a few local sparks who I normally assist/fault find for and they are struggling too. Customer is not well off financially but I might end up rewiring the place and paying for it myself just so that the fault won’t beat me ?

 

[Mikegh]

Might end up looking at getting DNO to monitor the incoming supply quality if you cant pinpoint something

 

[Grant1987]

I'd be checking myself anyway

Incandescent is the easiest to see it with

Is it dimming or actual flickering,

The dimming usually indicates the voltage drop

The flickering I'm not sure , maybe that could be indicating an external event altogether

Someone else wiser than me will probably be along with the right answer as usual

Its a combination of flickering and dimming it’s honestly a difficult one i would normally find the loose connection say thank you very much and walk out the door this one is no loose connection no faulty mcb no faulty rcd no faulty main switch so I don’t know. I honestly don’t know what the next step is other than changing consumer unit first which the customer can not afford so I’m in a difficult situation here ?‍

 

[Grant1987]

Might end up looking at getting DNO to monitor the incoming supply quality if you cant pinpoint something

My only issue with this is that none of the properties on the shared line are reporting the same issue

 

[Grant1987]

My only issue with this is that none of the properties on the shared line are reporting the same issue

I will ask the DNO to assess the voltage first though before I go paying out ?

 

[Mikegh]

Anyone else on the line operating equipment like welders or anything

Would be another query, not sure if it cause those exact symptoms, I don't know on that

 

[pc1966]

Having a logger attached to the incoming supply would reveal if there are volt drops prior to the CU, but not many folks have that. Maybe the DNO would do so?

 

[Grant1987]

Having a logger attached to the incoming supply would reveal if there are volt drops prior to the CU, but not many folks have that. Maybe the DNO would do so?

Yea I think I’m going to have to ring them today and see if they can assist at least then I can rule them in/out I’ve had faults in past where the DNO had loose connection with supply but this particular property is the mid point so it would affect the the properties downstream of the supply. It’s bugging me this one

 

[timhoward]

Having a logger attached to the incoming supply would reveal if there are volt drops prior to the CU, but not many folks have that. Maybe the DNO would do so?

I've hired one once, it was about £100 for a week. I think I paid over the odds too!

 

[marconi]

I assume you have done IR testing if not it would be a good idea to.

Is the fridge or freezer ( or both ) old albeit what comes next could apply to new/newish ones too. I wonder if the start capacitor of the motor driving the compressor is failing. If the start capacitor has a lower capacitance than required the motor will struggle to start and take longer to do so. This would be manifest as a higher starting current. This higher starting current may be further exacerbated depending on at what point in time of the mains voltage sine wave the motor is started - a random thing. I have seen something similar to this occur to single phase air compressors.

How to diagnose easily? Might the neighbour supply power via an extension cable to the fridge or freezer to see if the light flickering problems moves next door? The neighbour could be paid for a day’s worth of electricity to run the fridge - no more than a couple of pounds Sterling.

 

[Lucien Nunes]

If it is a loose connection or bad contact arcing and varying in resistance, it will usually be quite random in nature, sometimes tiny blips, sometimes longer and deeper brownouts, sometimes in quick succession, sometimes with long gaps. If it is a starting load or adverse heavy load causing voltage drop in an otherwise stable supply impedance, each event is more likely to be similar and follow more of a pattern. E.g. the compressor scenario will generate similar-ish events periodically.

A logger connected to the tails might not immediately indicate what the problem is, but would at least indicate who is responsible for fixing it.

 

[littlespark]

Look outside when it’s dark and look for sparking around the overhead lines.

Seen it before on a farm where a wet poly bag had blown over the wires…. Good job it didn’t light up his nicely stacked hay bales