problems with house lighting.

[neil3950]

Hello. I have recently moved into a bew build house and since moving in, I'm experiencing huge problems with light bulbs constantly blowing and in some cases transformers in light units burning out.

I will do my best to explain this logically and I hope someone may be able to point me in the right direction. The problem is restricted to the downstairs lighting circuits (looking at the consumer unit there are 2 cct brkrs fror downstairs lighting). As it was a new build we have replaced the majority of the supplied light fittings with our own on moving in. I have experienced the bulbs blowing in pretty much all of the light fitttings downstairs - some bulbs in one unit have blown 3 or 4 times. Also a couple of fittings I've purchased that have transformers in have blown - burning out the transformer inside. Additionally I found the twin & earth cable that supplies the light in the hall burnt and charred when I removed the unit recently. I am also experiencing problems with lights in some rooms flickering randomly for a second or so. The problem has affected approx 7 light units downstairs and not common to one circuit - lights on both downstairs circuits are affected. Not once has a circuit breaker on the consumer unit tripped when any of the bulbs have blown.

I have been in contact with the house builder to look into this, who sent in an electrician. I have since received a letter from them fobbing me off saying that the problem lies with my light fittings (I seriously doubt that I've purchased 7 dodgy fittings).

I will be very grateful if anyone can offer me any advice on what the cause of the problem may be? Thank you.

 

[plugwash]

whats the voltage like?

also if possible the supply clenliness should be checked. if a neutral breaks in a 3 phase part of the system it can create issues that aren't visible with a normal multimeter.

 

[neil3950]

I have not checked any voltages. My knowledge of house electrics is very basic

 

[Lectrician]

The charred cable is probably due to the way you installed the fitting.

Cheap lamp bulbs does play a huge part in the lamps blowing.

Do the fittings take halogen lamps - the ones with transformers will atleast. Are you aware you must not touch the halogen capsule of the lamp?? This decreases the life substantially!!

Flickering lights are probably due to a loose connection caused where you have changed a fitting on a loop in system - a loose or fractured live or neutral will cause the flickering.

 

[neil3950]

With reference to the charred cables - the fitting was installed correctly - well it was certainly electrically connected correctly.

Ref cheap light bulbs - in 3 months I've experienced 25 bulbs in 7 light fittings blow - some bulbs have lasted only a week - I would expect cheaper bulbs to last longer than that.

I am aware that you shouldn't touch halogen bulbs. The light fittings that had the internal transformers burn out did not blow their bulbs - just the transformers burnt.

I don't understand that with all the bulbs blowing and transformers burning out and even the charred cable I have that not once has a circuit breaker in the consumer unit tripped?

 

[Steve]

buy a cheap multimeter (£8 ), set it to volts ac and measure voltage between live and neutral on this lighting circuit.

 

[neil3950]

Thanks crafty. Where should I measure the voltage? At any switch or light fitting? What voltage should I be looking for?

 

[Lectrician]

A cable will charr and become brittle due to the proximity of extreme heat - the lamp bulb. A fault on the circuit would not cause a charring of the cable. What type of fitting is it where the cable has charred?? Some light fittings are poorly made, and are not designed for T+E cable to enter them directly.


I am sorry, but cheap lamps do blow time and time again. You get what you pay for. What type of bulbs are we talking - candles and golf balls? These are the worst for being made cheaply and not lasting for long periods.


Transformers in cheap fitings are also renown for burning out.


The MCB in the consumer unit will protect the circuit against overload and short circuit type currents. A loose connection will rarely cause the breaker to trip, and a charred cable certainly wont unless the cables insulation is breaking down or severely damaged causing copper to copper contact. It may however trip when bulbs blow - although you say it hasn't - count yourself lucky.



Measuring the voltage is unlikely to uncover a problem. If you had overvoltage, lamps on other circuits, including table lamps etc would also be effected. If it was a dropped neutral on a TP supply, you would find all kinds of electronic kit behaving spasmodiclly, and breaking down, and notice the voltage rise and drop substantially.


If you feel you do have a problem, get a spark out to take a look, and if you feel it is a supply fault, ask the DNO to install a line monitor.


Personally - just buy some decent lamps like osram or crompton, re-terminate the fitting correctly, taking account of heat at the fitting where the cable has charred, and locate the loose cable at one of the light fittings causing the lights to flicker.

 

[neil3950]

Thanks lectrician - some useful points there. I'll try and answer the comments.

The burnt cable is charred and brittle and thinking about it could be caused by heat from the bulb. the light fitting is a square ceiling mounted unit (approx 8" square and 2" deep and contains a 100w halogen strip bulb).

The other bullbs that are blowing are a mix of candle, halogen stip and pearl bulbs. I have been buying decent bulbs - the last halogen one I bought I paid extra as it was guarenteed for more hours. The 2 fittings that had the transformers burn out where v. expensive (approx £80 each) so I'd of thought they would be decent quality.

I think I'll go and check all the termination points where I've installed fittings. The amount of problems I have had just seems very strange and I'm concerned that there is a problem associated with the initial installation of the wiring in the affected circuits when the wiring was installed during the house build?

 

[plugwash]

i think its far more likely that there is a problem in the suppliers network but without the proper test equipment its very hard to find out.

 

[Lectrician]

i think its far more likely that there is a problem in the suppliers network but without the proper test equipment its very hard to find out.

This would then be circuit wide, not contained to this single circuit.

 

[plugwash]

ahh sorry didn't notice that bit in the original post.

 

[HDRW]

i think its far more likely that there is a problem in the suppliers network but without the proper test equipment its very hard to find out.

This would then be circuit wide, not contained to this single circuit.

He did mention that there were two circuits for downstairs lighting, strangely, but it isn't clear whether both of these are involved or only one.

If it is just one circuit, what sort of wiring fault could cause bulbs to blow?

Cheers,

Howard

 

[HDRW]

Thanks crafty. Where should I measure the voltage? At any switch or light fitting? What voltage should I be looking for?

Switches don't usually have Neutral, so you really need to measure at a light fitting, but it's quite a dodgy thing to do as you are obviously working live. Don't try to poke the two meter probes into the fitting where the bulb would go - the chances of shorting them out are very high, and the resulting sudden release of energy is a Bad Thing!

Make sure you have a decent stepladder (you don't want to be wobbling around while you connect to live wires) and test at the connections inside a ceiling rose. Put one probe on the Neutral, the other on either the permanent live, or if the light is switched on, onto the switched live (that is, you are measuring across the blue and brown of the light fitting).

Make absolutely sure you don't make contact yourself with metal on either of the meter probes or any of the wiring at any time! Keep your fingers behind the plastic guard-rings.

You should find something in the region of 230 to 240V (make sure you have the meter set to AC, and if it has ranges set it to at least 300V - the cheap meters often have 200 and 750V AC ranges - go for the latter). If there is someone else there who can read the meter while you concentrate on placing the probes, so much the better.

The maximum you should see is 230 + 10%, or 253V. If it goes above this, you need to talk to your supplier as they are outside their specs.

Finally, you don't have dimmers on the halogen lights, do you? That severely reduces their life, although they don't tell seem to you that when you buy them!

Best of luck, and be careful...

Cheers,

Howard

 

[neil3950]

There are 2 lighting circuits for downstairs and 1 for upstairs. (well I presume this is the case as on the consumer unit there are 2 circuit breakers for down and 1 for up. The problems are isolated to the two downstairs circuits, upstairs has been fine. Also I have had no problems with any equipment connected to wall plug sockets. There are no halogen bulbs on dimmers.