Fluorescent light fire, how?

[ericmark]

Been reading a report about a fire caused it says by a fluorescent lamp today.

Seems not too much damage, but two fire appliances attended, and I wonder how, what can go on fire with a fluorescent lamp? I suspect a LED replacement tube, not really a fluorescent, but this is a worry, if LED tubes can burst into flames, then this is rather worrying.

 

[SUNRAY]

More likely to be an overheated choke I feel.

In the early days when tubes had BC ends and starters were on SES bases chokes melting were a known problem. Hence regular monitoring of operation in larger installations was common.

 

[Adam_151]

Seen such things when magnetic chokes have failed, majority of the time, they get a bit hot, smell bad and then trip the breaker. But during the getting hot stage they can cause issues if its prolonged and the fitting is mounted to a combustable surface, I think some of the worst were the plastic cased 2D fittings when they were switch start, but even the metal cased batten fittings could still cause problems if fixed directly to wood.

A couple of years ago a factory round here burnt down due to a light fitting: https://thelincolnite.co.uk/2020/06/firefighters-find-the-cause-the-of-north-hykeham-factory-blaze/

 

[ericmark]

It seems we were lucky, and damage is light, and the heritage coaches were undamaged, I know our electrical engineer loves LED so suspect this was an LED tube in a fluorescent fitting, we must have 100's of these, so if there is a fire risk, it is a major problem, as many of our buildings have no fire detection devices, they don't work very well around steam engines, or rather they do work, when we don't want them to.

 

[Adam_151]

@ericmark How have the fitting been converted? just by putting a LED tube in a switch start fitting and putting the retrofit 'starter'/fuse in? or properly by cutting the gear out of circuit and putting power stright to the tube?

I'm not sure that there are many detectection technologies that will avoid triggering from a steam engine and still reliably detect a fire in a large shed, I suppose you could have an arrangement where certain zones (or points) have to be disabled when the steam engine is in use, but that likely becomes a hassle and someone will forget to disable or renable afterwards. I think we are just starting to see arrangements that use AI to monitor an array of thermal cameras and alarm on anything outside the unexpected, but these are rather specialist and very dear. I've only seen consideration given to them when the insurer has more or less demanded it*, and IIRC it was linked to a water deluge system** with pumps backed by standby generators. (but that is because its appropiate to this site, but woulnd't be to most, most would just require alarm/fire bridgade response)

* Think something like 3 fires in the 10 years the site has been built. ** The contents of the building are of very low value and flooding them with water is not a big concern, there might be minor clean up costs, but thats it

 

[bernardgreen]

More likely to be an overheated choke I feel.

That was ( still is ) the reason for most fires in fluorescent light fittings.

Vibration of wire in the coils could abrade the insulation resulting in shorting turns and subsequent overheating.

Coils that had been vacuum impregnated with resin were least likely to fail,
Vacuum impregnation with a high melting point temperature wax reduced the risk of the choke failing.

 

[AdrianUK]

Another scenario I've seen a few times.....

A failing lamp is ignored. The starter keeps trying to start the failed lamp, the lamp blinks & tries to start many many times. Eventually the starter fails short. The heaters in the lamp now run permanently with just the choke acting as a current limiter. This causes the choke to overheat & start to smoke.

 

[securespark]

Yeah, chokes can get red hot.
I have seen burnt laths in old ceilings where the plaster is missing and chokes have overheated.

 

[SUNRAY]

Another scenario I've seen a few times.....

A failing lamp is ignored. The starter keeps trying to start the failed lamp, the lamp blinks & tries to start many many times. Eventually the starter fails short. The heaters in the lamp now run permanently with just the choke acting as a current limiter. This causes the choke to overheat & start to smoke.

Yes and I believe this was probably more common with the larger starters I mentioned in #2, I think the more recent style was more likely to fail open circuit, I'd like to think by design.

 

[AdrianUK]

.... as many of our buildings have no fire detection devices, they don't work very well around steam engines, or rather they do work, when we don't want them to.

Have you looked closely at some of the more modern addressable systems? They can get quite clever, for example, with our system at work some zones run as heat only detection during the day but, when the intruder alarm is set at night, then they change to smoke detection as well.

 

[foxhole]

Any electrical fitting or wiring has a potential for causing a fire.

 

[333rocky333]

Was called out to a Tesco once, one of them dustproof fittings with the plastic covers on, the starter failed and the tube ends glowing red hot, this in turn melted the plastic material, this dropped down onto a cardboard box and set that on fire, this was inside a walk in freezer, luckily the fire was only contained to a small area, I quess due to the damp environment, but still needed fire brigade attendance

Had many calls to burnt out chokes but these generally smoke and smell, older fittings used to pack the paper instructions beside the choke, often these are found scorched years later

 

[ericmark]

I will likely find out on Wednesday what happened, we were it seems very lucky, nothing in the shed was damaged. I was unaware we had any fluorescent tubes left, and reason for post was wondering if converting to LED could have been the problem, but it seems fluorescent fittings can go on fire, I was just wondering how a metal unit would go on fire, and most the plastic ones are claimed as flame proof, so again seemed unlikely.