HELP MY CEILING LIGHTS (BULBS) ARE BLOWING UP !!!!!!!!!!!!

[Nicetoseeyoutoseeyounice]

Right, 18 months ago our house was rewired which was then independently inspected, NICEIC certificates and all. A few months ago several light bulbs started blowing sometimes glass everywhere. Now this is no conincidence but they were from the same store and same make. This has never happened with any other bulb at all. I of course complained to the store who have said they can find no fault with the bulbs as they have had no other complaints.

NOW I KNOW THIS IS NOT A CONSUMER HELP SITE.

BUT, this is where DIYNOT comes in. If it is not the bulbs then could I have a fault. I can truthfully say though this has NOT happened with any other make of bulb which I have and have had in the same ceiling lights. Can anyone help on this as if there is a fault it could prove a lot more dangerous than just the light bulbs blowing. As usual I know I can rely on you lot.

 

[kwikfix328]

What type and brand of bulb are you using.

The house that i currently live in was the worse one ever for blowing bulbs, they hardly lasted a few weeks regardless of the brand or price.

Since switching over to low energy CFL's I haven't changed a light bulb in years ( unless I've broken it ! ) and they are cheaper to run...

 

[electronicsuk]

If the lamps are mains voltage, the light fittings are correctly mounted as per the instruction manual and you aren't having problems with short lamp life elsewhere in the house then it's probably down to poor manufacturing.

If the fittings themselves aren't being used correctly, for example mounted upside down or covered with insulation, then excessive heat buildup could cause the lamps to explode.

What type of lamps are you fitting, and what type of light fixture are they in? If it's got a transformer then it's possible that it could be faulty leading to excessive voltage on the output.

 

[RF Lighting]

Relax !!! This problem does not mean you have a major wiring fault. This is a never ending problem which has been looked into for donkeys years. A wiring fault in your circuit will be picked up by fuses and MCB's long before it gets to the bulb.

There are a few reasons bulbs can blow, the major one being cheaper bulbs. The elements in cheap bulbs are much thinner and any surge of power, however slight, simply breaks them. Always go for expensive light bulbs, its cheaper in the long run.

A loose connection in the lamp holder can also cause bulbs to blow. This is because the circuit is not completed as tightly as it could be and the electricity may have cause to "arc" or jump across the contact, rather than simply flowing through it. When this happens it produces more heat in the fitting than is expected or catered for by the bulb, and the bulb can blow.

The same can happen if the spring loaded connection in the bulb holder is slightly loose. This will cause electricity to arc across the contact, cause too much heat and blow the bulb. This can very often be diagnosed by looking at the contact on the bottom of the bulb to see if it is pitted. Arcing electricity effectively melts the metal it is arcing onto ( This is how arc welding works) so if the bulb contact is being subjected to arcing, tiny little indentations occur, called pitting.

It is sometimes possible, if the live connection in your light switch is a little loose, for this to happen here also. Heat will be generated and it is possible, though very very remote, for the bulb to blow as a result of this.

When a bulb blows, 99% of the time the fuse for the lighting circuit will blow or trip also. This makes the problem seem rather bigger than it actually is. The reason for a blowing lamp tripping an MCB is that the lamp element gets thinner during its life to the point where it breaks at the thinnest point, this point will melt just before failure. The resistance of the overheating element will momentarily be very low and a current surge is caused, this is picked up by MCB's but generally not fuses.

So, three things to look into if your bulbs keep blowing. Your bulb supplier, The wire connections inside your bulb holder, and if the spring loaded connectors are working properly inside the bulb holder. As a last resort you can also check the tightness of the connections in your switch.

 

[2scoops0406]

The resistance of the overheating element will momentarily be very low and a current surge is caused, this is picked up by MCB's but generally not fuses.

Quivering slightly, but is this true ?

Conductivity of tungsten, courtesy, of t'Internet.

Electrical Resistivity @ 20 ºC (microhm-cm) 5.5
Electrical Resistivity @ 227 ºC (microhm-cm) 10.5
Electrical Resistivity @ 727 ºC (microhm-cm) 24.3
Electrical Resistivity @ 1727 ºC (microhm-cm) 55.7
Electrical Resistivity @ 2727 ºC (microhm-cm) 90.4
Electrical Resistivity @ 3227 ºC (microhm-cm) 108.5

Hence why superconductors are cryogenically frozen to lower their resistance.

I think it maybe more to do with the filament rapidly evapourating, hence the resistance going up, but nothing directly caused by the heat, until of course this starts making the tungsten gaseous.

 

[RF Lighting]

Dunno. I just copied and pasted that text from another site

 

[ban-all-sheds]

I've always understood it to be that when the filament breaks you get an arc inside the lamp, and as arcs do, they create plasma which gets lower in resistance as it gets hotter, leading to a brief but large current flowing.

Sometimes the filament gets burned up and the arc collapses before the breaker trips, usually it doesn't.

 

[Paul5152]

FWIW, when we first moved into our house we had a big problem with normal bulbs blowing regularly in our house (though not physically exploding). CFL bulbs are fine.

We even had a couple of 12V lighting transformers die which was a real pain.

A bit of experimentation found that our mains voltage was fluctuating between about 250 and 280V. (It's meant to be 216-253V)

We had the electricity distribution company round who installed a supply recorder for a weeks or so. After they looked at the results, they actually went up the road and took a different tap off the local supply transformer to bring the voltage down to a more normal value. (They didn't want to bring it down to the proper voltage because that would need a whole new transformer. They were happy to do it if we pushed for it, but asked us to try with the modified version first).

After they did this change it's a lot better now. Bulbs last about 6 months now rather than 2-3 weeks as they did before. Apparently the problem was because we are rural, and we are on the same transformer as a farm (just 3 or 4 buildings are on this transformer). When the farm had lots of machinery it would load the system, so they needed to put the voltage higher than normal so the load would drop it to the correct value, but when the farmer retired, the load dropped, so the voltage increased.


I noticed the higher than normal voltage because a computer UPS kept switching to backup power because the supply voltage was too high, even on the most lenient setting. I used the UPS's software to record the voltage which was showing it regularly high. Then I got my multimeter out to verify the UPS's results (take care if doing this!)