In my kitchen, there's a light fitting with four GU10 mains halogen bulbs in it.

Ever since it was fitted, a bulb has blown about once every two weeks. Bearing in mind that the light is only used for 3 or so hours a day, this makes no sense. It's not the same bulb blowing every time, and I've tried different brands with no luck.

Anyone know why this could be happening? It's getting expensive now as these bulbs aren't cheap...

Overheating maybe?

Since you said it's not the same one each time, and you've replaced them with different brands, then how many brands have you tried and how many times have you replaced a bulb? Have any bulbs of a particular brand lasted significantly longer than other bulbs of the same brand? Like, have the original 4 bulbs all blown by now or what?

I'm just trying to see if there is any sort of pattern at all.

Thanks for the reply.

The light fitting is quite well ventilated - each bulb is on the end of a stalk with a loose fitting vented metal case over each one. I don't think it's overheating, but it is an interesting idea I didn't think of.

I've been looking for patterns too and I can't see any. At first I bought cheap bulbs (£1.50/$3 a pop) which I thought were the problem. When they blew a few times, I replaced them with expensive Ring ones at just under double the price. These lasted the same time though...

It's driving me mad, turning on the light and finding a blown bulb so often... Sometimes a fresh one will pop after only a couple of days, other times a couple of weeks. I started writing down which bulb was replaced one and I can't see a pattern...

Since it is a halogen make sure when you replace it you hold the new bulb with a clean cotton or paper towel and do not allow your skin to come in contact with the bulb. The oils in your skin can fuck up the bulb.

Check the voltage on the socket with a multimeter. Perhaps it is lower or higher than it should be. The electrician could have fucked up. Assuming you live in the US, it should be 120V plus or minus 5V (maybe 10). If it's high or low, there's your problem.

Mains voltage is fed in through one single phase main into the house so it's the same voltage throughout every ring. It's impossible to screw up and wire a light fitting to have a higher voltage. Some older houses have three phases coming in though; typically one is used for lighting, one for high current stuff like the cooker and one for sockets.

Besides, I fitted it myself. ;)


PS. Mains voltage in can vary from 110 to 130v in your case - more if you're far from a substation with bad wiring. It's about 230v max RMS over where I live in the UK as I'm quite close to a substation, although in the evening it drops to 220v. In case you're wondering why I monitor it so closely, my stereo's power conditioner has a voltage display on the front...I'm not OCD with a meter. :D The cleanest, highest voltage is normally in early morning (think 4am...) when there's not much usage.

I'm starting to rethink the overheating point as the metal shields do get very hot - thanks for that, emag. I've just taken off two of the shields leaving the exposed bulb in its holder to see if it makes a difference.

Besides, I fitted it myself. ;)Well there's your problem
;)
...I'm not OCD with a meter. :D The cleanest, highest voltage is normally in early morning (think 4am...) when there's not much usage.Well I am, so I'm going to have to start checking that out. :)

At first I bought cheap bulbs (£1.50/$3 a pop)Hey, a pound is only worth <$1.50 now :D

The wire going to that specific bulb could be frayed.

In my experience of being an electrician, usually it is a loose connection, or a bad socket that causes them to blow. As far as voltage, if you have lower voltage than 120, you will get more life out of it. Dimmers can more than triple the life of a bulb cause they cut the sine wave down and reduce the voltage. Check / Re-do your connections, check everything in the socket though it may be an internal problem, and make sure all the contacts are out to make good contact with the bulb.

Thanks for all the replies.

I've just double-checked and re-tightened all the connectors, and taken apart each light fitting to check the wiring which was factory fitted too. Nothing out of the ordinary here though...

Sentinel, it's a brand new light fitting and I can't see why a high resistance wire (i.e. frayed) would cause bulbs to blow quicker? Surely it would be the opposite? ;)

Not so much high resistance, but loose connections. If a connection is partially broken, the current will arc, forming an inductive pulse. This induces a high voltage pulse, which could damage the bulb.

Woah, don't do too many things at once or you may never know exactly what the problem was :p

I would explore a dimmer or soft turn-on circuit.
Not sure about halogen, but most incandescent filaments blow when initially turned on.

Surprised no one has suggested to check the wattage in the bulbs yet. If you're putting the wrong watt bulbs in, that would be the problem. Most fixtures I've seen have a label directing what watt bulb to use.

Check the wattage on your fixtures and bulbs and make sure you're not under lamping your fixtures.

Surprised no one has suggested to check the wattage in the bulbs yet. If you're putting the wrong watt bulbs in, that would be the problem. Most fixtures I've seen have a label directing what watt bulb to use.

Check the wattage on your fixtures and bulbs and make sure you're not under lamping your fixtures.Wattage ratings are only given so that you don't overheat the fixture melting the wires and causing a short. All fixtures can power any wattage bulb just fine, the only difference is how much heat they can dissipate.

That being said, it's still a legitimate possibility that the wattage could be the issue. If the bulbs aren't the right wattage this would cause them to overheat, causing the short lifespan of the bulbs.

A legitimate possibility that has already been addressed.

Idea number 2 then: The light fixtures are junk. What brand are they? Some off the wall brand from a hardware store, or something name brand like lightolier?

As long as the fixture is well ventilated, I don't see why build quality would be an issue. After all, the light fitting only has to connect the bulb to power whilst keeping the bulbs well cooled. The bulbs match the maximum wattage too.

They're a house brand from a hardware store by the way.

I've seen enough shitty light fixtures to know that sometimes the brand is the issue. All made in china light fixtures are not created equal. You think: well what the hell, the fixture just has to come from the mains, through some wire, to a bulb. The cheap Chinaman thinks up the cheapest and most unreliable way to do so.

I've had faulty wiring in a fixture blow an entire riser to an office building before. A master electrician even inspected my work (I'm an electricians apprentice) and came to the conclusion that it was a bad fixture.

On the same job, I must have installed over 80 recessed lights, and out of that 80, at least 10 of the fixtures were bad.

When it's something that has the potential to burn down your house, trust me, brand matters.

Short somewhere in teh circuit making too much current go thru bulb?

Halogens get VERY hot. That's how they work.

Just install a fuse if you don't want to track down what is most likely a short. At least they are cheap as fuck compared to a new bulb. Maybe a circuit breaker would work too, but I'm not sure if you can buy ones for such a small application.
Use a fuse that is a few hundred mA over the bulbs rating so it doesn't blow every time you turn on the lamp. If it is a short it is probably a few amps that is blowing the bulb, so you have a bit of headroom.

Eh? Short circuit = less current going through the bulb. The short has a lower resistance.

Anyway, thanks for all the replies. The two bulbs where I removed the metal shields so far haven't blown, whereas the other two have both been replaced twice.

I guess it was overheating! Thanks emag. :D I'm probably going to end up buying a new fitting as I didn't really like the spotlights...too many annoying shadows.