What could cause halogen bulbs to explode?

Question

I changed several halogen spotlight bulbs and after less than one hour, one exploded. See image.

It's an Osram Decostar, 35W. Although the bulb doesn't carry a "CE" mark, the box did.

We regularly have bulbs dying, so I suspect something might be wrong with our wiring, but I don't expect the bulb to explode. Usually they just die quietly.

My real question though is the root cause. What could be wrong with the electrics?

I checked the dimmer switch wiring and it is correct (with switched-live in L1 connector). Is there anything else I can check for?

So you're saying it could be sweat/grease on the bulb from when I installed it? I guess I'd better clean all the others and fit them with velvet gloves then! — Tim, Jan 24 '18 at 11:37
Doesn't need to be velvet gloves; cotton or latex is fine :-) (or even using a tissue or paper towel between your hand and the bulb). — fixer1234, Jan 24 '18 at 11:42
"One exploded after an hour" as indicated by @fixer1234 this is caused by finger oils or other contaminates on the lamp envelope itself (not the reflector). "We regularly have bulbs dying" is likely a socket problem, replace the bi-pin socket the lamp plugs into. When heat is generated by the lamp pins this type of bulb will prematurely fail. (I know as hot as the lamp gets while burning this is hard to reason, but when the bi-pins generate heat from poor connection the result is premature failure.) — Tyson, Jan 24 '18 at 13:16
Thanks. I will likely replace the whole lot with LEDs anyway, but certainly want to avoid further explosions in the short term. If anyone wants to expand the grease issue into an answer, I'll accept it. — Tim, Jan 24 '18 at 13:52
@Tyson please make your comment into an answer there are many folks who are not aware of the special care that halogens require. — Kris, Jan 24 '18 at 13:56
@Kris I didn't originally because fixer1234 was ahead of me with the thought. I did find enough other to convey tho that it's now become an answer. — Tyson, Jan 24 '18 at 14:29
CE means nothing, it means the builder swears on a stack of bibles that they used non-leaded solder when they soldered it, and other trivial EU requirements, mostly environmental and not safety. Nobody checks this. There's no testing lab like UL, CSA or TUV. Look for those marks. — Harper - Reinstate Monica, Jan 24 '18 at 18:09
"We regularly have bulbs dying" - because these suck big time. A place I worked had a display hallway with like 50~100 of these. Dude had to change at least one bulb a day. They finally gave up on them and installed track lights. — Mazura, Jan 24 '18 at 22:30
@Harper non-leaded solder is the ROHS mark the CE sign indicates that the manufacturer declares that he obeyed the relevant European product safety norm and can be sued if he did not — Martin, Jan 25 '18 at 08:32
@Tim When replacing with LEDs, try with ones you can easily return. Their light is vastly different from halogen light and the effect that halogens were designed to create is often not replicable, at least not with drop-in replacement LEDs. — Agent_L, Jan 25 '18 at 11:42
@Agent_L Thanks for the tip. I'll also be avoiding ones with permanent, integrated bulbs for the same reason. — Tim, Jan 25 '18 at 11:58

score 26 · Accepted Answer · edited Jan 25 '18 at 17:59

"One exploded after an hour" as indicated by @fixer1234 this is caused by finger oils or other contaminates on the lamp envelope itself (not the reflector). Its very important not to touch anything but the outer edge of the reflector.

Further what type of fixture is this bulb being used in? If the fixture is open faced situation such as this: then the MR16CG must be used, (the CG stands for "Cover Glass") which has a self-contained lens. I mention this specifically because CG versions of the bulb tend to be harder to find and many people don't know when to use the CG version VS when the open face bulb is ok (i.e. enclosed fixtures).

"We regularly have bulbs dying" is likely a socket problem, replace the bi-pin socket the lamp plugs into. When heat is generated by the lamp pins this type of bulb will prematurely fail. (I know as hot as the lamp gets while burning this is hard to reason, but when the bi-pins generate heat from poor connection the result is premature failure.)

In the end, the best advice is to give is find an LED replacement that you are happy with. Unfortunately in many situations the MR16 halogen type of bulb is the hardest to replace with LED. It's very difficult to find LEDs that burn as brightly and with the colour clarity of the original - highly energy inefficient heat generating - halogen.

Many thanks. I've seen some 6W LEDs that claim to give 450lm/3000k. My current halogens are 430lm/2900k - so pretty close on paper. — Tim, Jan 24 '18 at 14:56
Epic answer, your knowledge really shines through. Wish I could more than upvote. — Harper - Reinstate Monica, Jan 24 '18 at 18:10
Spot-lightning is pretty much out of question for LEDs. As a rule of thumb: LED lamp comes with it's own socket. Drop-in replacements are merely a substitute. @Tim Check the light distribution angle as well because 430lm over 60° is "very dim", while over 10° is "very bright". — Agent_L, Jan 25 '18 at 11:40

Ed Beal · Answer 2 · 2018-01-24T14:37:03.047

Halogen lamps are very sensitive to oils because of there high operating tempature. Oils from fingers cause a hot spot on the envelope and this hot spot can melt causing the lamp to explode. I have seen reflector types also have early failures on high power projectors. when removing the lamp from the package use a tissue so you never touch the lamp (don't use tissues with softners or creams). If you do touch the lamp some rubbing alcohol on a tissue can clean it off just make sure it is dry before turning on. The life on some of these lamps is only 200 or so hours when run at the rated voltage. I was surprised by this when checking a fixture out for a friend. I added a dimmer that had a upper limit control to reduce peak voltage and that almost doubled his lamp life.

What could cause halogen bulbs to explode?

2 Answers2