Failure mode for undercounter lights

[Cigaro]

I left my floursecent under-cabinet kitchen lights switched on last night, and when I came home today there was a funny smell and they were no longer working. After checking for voltage at the plug I decided to actually have a look at the lamp and one end has melted itself into the holder, deforming the plastic diffuser too!

Bit of an odd failure mode. How can this even happen? Obviously I know it doesn't point to a problem with my electrics in any way, it just seems... strange. Also slightly worrying, given that it could have potentially started a fire.

 

[phatboy]

Were the lights a respectable brand, or something from the internet with an unknown origin?

 

[bernardgreen]

The 4 pin flourescent tube has heaters at each end. Via the starter these heat up to excite the molecules of the gas in the tube. When gas in the tube becomes conductive the starter detects it and turns off the heaters.

In most case the tube strikes and the heaters turned off before they reach red heat.

A faulty starter or a tube that stops conducting can leave the heaters on permanently and they can glow red hot. It appears your lamp holders cannot handle the heat if the heaters are permanently on.

 

[Steve]

Bernard, most modern undercupboard (specified for this use) lights are T4 or T5, and are actually fully electronic. Certainly mine light immediately.

Though if the OP has just bought a standard T8 fitting from B&Q its more than likely a horrible magnetic choke and starter setup which will flicker on startup and humm in use.

 

[bernardgreen]

Steve
Some electronic flourescents do heat the heaters until the tube strikes. There is no starter as such because when the tube strikes the limited power from the electronic "choke" goes into the low impedance circuit through the tube leaving very little for the higher impedance heaters.

 

[Cigaro]

They were a respectable make, I don't know which one but I got them from CEF and I don't think they sell substandard crap (or maybe... )

Makes more sense if they're a conventional flourescent with a heater - for some reason I was thinking they were CCFLs.