Kitchen Light flashing

[sherman0251]

Hi was at a job today as they said there kitchen light was flashing at odd times during the day. They already had 2 electricians out previous to me and they couldnt solve it either! Both replaced the light thinking it was a faulty light, so in all it has had 3 fluorescent lights??????
When I went today I knew it couldnt be a faulty light. I checked for voltage at the fiting and 240v as expected, I then traced the cable to a junction box under the floor and dissconnected it. I connected the cable onto a new 1.5mm and took that back to the distribution board so that the light was fed directly from a 6A breaker via a light switch. Tested R1+R2=0.21 ELI was 0.71

Got a phone call about 4 hours later saying when they turn the oven on the light starts to flash again so they turned it off and the light stopped flashing, then once again turned the oven on and it started flashing again!

Any ideas?? im stumped without stripping down half the electric board??

 

[Spark123]

Try measuring the voltage with the oven on?
Could be a loose connection upstream.

 

[sherman0251]

When u say upstream do u mean at the distribution board? Busbar?

 

[Spark123]

Aye, could be. Try the voltage at the fitting, voltage at the CU, voltage at the tails and if it proves to be low then you may end up phoning out the DNO.

 

[Steve]

Is it a switch start? Or electronic/digital? Fitting the latter may help.

 

[sherman0251]

Could you explain how fitting a hf fitting could be better? Excuse my ignorance! Are you saying that if the incoming voltage is lower than normal then when a piece of high current using equipment is turned on the voltage drops on other circuits?

 

[Steve]

I have a couple of switch start fittings in my shed. And they flicker quite badly sometimes. Now whether this is volt drop because they are a distance from the house, or because of the low temperatures they operate in, I dont know. But I know a HF fitting wouldnt exhibit this flickering - you might get bands down the tube, but no actual flickering. You could try one out for them.

Of course, I assume you have changed the lamps and starters each time?

 

[Steve]

Are you saying that if the incoming voltage is lower than normal then when a piece of high current using equipment is turned on the voltage drops on other circuits?

No. Anyone with an electric shower will have seen this:

When you turn on the shower, your lights dim*. This is voltage drop on the line that feeds your house. Due to the high load (10kw) on the line, the volts drop. A way to improve this is to increase the incoming service cable, but the DNOs spec according to 2kw average demand per house.

The normal voltage can be totally in spec (235 volts) but when a high load is introduced it can loose about 20 volts.

*CFLs dont experience this phenomenon due to their wide voltage tolerance.

 

[RF Lighting]

Is it a switch start? Or electronic/digital? Fitting the latter may help.

That is a bit like papering over the cracks.

Have you seen the light flashing? Does it actually flash on and off, or is it more of a flicker?

 

[sherman0251]

No I haven't actually seen it flash but customer just said it flashes so I would presume on and off! I think I'll have to do wat was suggested and measure the voltage at the fitting when oven off then turn oven on and see wat I get! If it is the volt drop causing the problem then maybe get another type of fitting??? Want to try and minimise the amount of visits to the property!

 

[RF Lighting]

You need to go in with your volt meter and take a L>N, L>E and N>E measurement at the fitting and also again at the top of the CU main switch.

Then load the system up with the oven, lights, heaters etc and retest the same points again.

If the voltage stays constant(ish) at the CU, then the fault lies within your installation, and if it varies quite alot then it is a DNO problem.

In my experience the supply would have to dip below ~200V for a fluorescent to start having trouble. It will be normal for the supply voltage to drop a few volts when it is heavily loaded.

If you have an analogue meter use it. They are often more reliable / easier to interpret than a digital meter with this sort of fault.

All the above is assuming a problem with volts drop. It could of course be something entirely different.

Did you confirm polarity and Ze while you were there?

 

[ban-all-sheds]

When you turn on the shower, your lights dim*.

Mine don't.

And they aren't all CFLs.

 

[Steve]

When you turn on the shower, your lights dim*.

Mine don't.

And they aren't all CFLs.

You got an 11Kv supply? Or is there a substation next door?

 

[martinxxxxxx]

Hi

If you have not seen the problem yourself, maybe you could ask the customer to video it with his/her phone next time it happens and also make a note of any other appliances that were being used at the time.

I would used a data logger to measure the voltage overnight.

Does the customer live alone. If so get them checked for eyelid myoclonia.

Martin

 

[ban-all-sheds]

Or is there a substation next door?

It's a few '00m....