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October 29, 2010


Dave Dorosz

The question I have is why does the position of the CFL cause it to overheat and melt? Hot air rises so maybe I can see how an upside down vertically mounted bulb would overheat, since heated air from the lamp would rise toward the base. But in a horizontally mounted lamp, this wouldn't be the case.

Carl Schwab said that he has mounted some CFL lamps upside-down vertically and horizontally with no ill effects (although we may have to wait until he takes a second look at them and reports back) if so, why do some CFLs work without regard to how they are mounted while others fail in a dangerous way?

Bill B

By whom are we told that these bulbs must only be installed base down? I have inspected the bulbs and their packaging in reaction to your report and can find no such warning. I would like to learn more. Can you cite your source?

Your pictures indicate that there is definitely a design or process flaw with the items you have.

Rob Legg

You'll find that the actual hot-spot temperatures of the compact CFLs are no-where near those typical of their incandescent counterparts. This is the only reason why thermoplastics are even allowed in these assemblies.

You should also be aware that the thermoplastics are by no means the most temperature-sensitive part of the assembly - reliability wise.

Early discoloration of the plastic base is a sign of poor or defective tube construction. If the part carries some kind of guarantee, you might have a case if it actually fails to light up as intended - which it may do at an earlier-than-anticipated time - but I don't see an actual fire hazard here, just an iffy product quality issue.




I have been using CFLs for over 25 years and I have not seen this type of failure. I've used various different types and makes including some of the early Philips SL bulbs which were just conventional fluorescent lighting units folded up into a smaller socket-fitting lamp assembly. Some of these lasted 20 years and it was the tubes that wore out eventually.

I have had cheap CFLs of dubious origins that have blown their switch-mode supplies sometimes at first switch-on but have not seen signs of overheating such as yours on any of them no matter what make and how long they last.

Most of them have been used dangling bulb down from the ceiling, some inside small unventilated fittings in bathrooms where they would get hotter than in open shades.

The biggest differences I can see between yours and mine are:

i) I live in the UK and so am running lamps from a nominally 240V 50Hz supply.

ii) my lamps have all been folded rather than spiral tube layout.

Quite why (apart perhaps from poor PSU design!) this should make so much difference I'm not sure.

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