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!!!

 

[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

 

[7029 dave]

It could be loose connections in the cutout.

 

[littlespark]

If everything’s been checked in the board, then it must be outside the consumers installation and must be investigated by DNO.

 

[7029 dave]

If everything’s been checked in the board, then it must be outside the consumers installation and must be investigated by DNO.

Sounds like a job for the DNO

 

[Dave OCD]

I've had a 100 amp main switch cause similar issues which were quite hard to pinpoint initially. It had developed a resistance on the neutral which caused intermittent low voltage depending on the load being used. That particular switch was an MK .

 

[marconi]

Grant1987 - what Sir is the earthing system in the home? Are the overhead lines marked pme or can you see the lower neutral conductor connected to an earth electrode at some/all of the wooden poles? Has the overhead been modernised to (the ugly IMHV) 4 cable ABC viz aerial bundled cable?

Any electric car chargers in the street?

 

[Lucien Nunes]

It could be loose connections in the cutout.

I've had a 100 amp main switch cause similar issues

If it's either of these or the meter, it might be possible to provoke it by thumping the meter board. A bad connection or contact that heats but doesn't flicker isn't always ticklish but one that flickers often is.

 

[marconi]

Developing LN's #26: What you could do is to load up the supply to cause Ohmic heating of items like the Main Switch, Cut Out, Meter and any Henleys. A shower, conventional tumble dryer and some electric heaters all on high would be ideal since they would be on more than off. You could use the electric hob and oven but after while this load will cycle on and off and its average power/current will fall to a lower value.

 

[Dave OCD]

As long as he puts a few shillings in the meter first. ?

 

[Grant1987]

Grant1987 - what Sir is the earthing system in the home? Are the overhead lines marked pme or can you see the lower neutral conductor connected to an earth electrode at some/all of the wooden poles? Has the overhead been modernised to (the ugly IMHV) 4 cable ABC viz aerial bundled cable?

Any electric car chargers in the street?

It’s marked as a pme system and all readings come back satisfactory. Also not sure who asked about IR test but I also done that and readings were high in the hundreds so can rule out poor insulation. I’ve contacted DNO they are coming out next week. I’ve supplied customer with LED lamps and they’ve said it seems to have eased the flickering but still briefly shows signs of dimming/flickering. I’ve read a post on here of faulty main switch which sounds plausible same as rcd but it’s occurring in 2 x rcds so I’ll be better off changing the lot. Then after the DNO disregard the fault being on their end I’m going to change all light fittings and switches then I’m going to change consumer unit.

 

[Grant1987]

If it's either of these or the meter, it might be possible to provoke it by thumping the meter board. A bad connection or contact that heats but doesn't flicker isn't always ticklish but one that flickers often is.

I will happily thump the consumer unit and the customer ? told them to ring fellow sparks but they’ll be in same boat as me as I’ve spoken to them all. Well the ones I like us sparks do sometimes create a divide you all know what I mean ??