The Lamp Room

Hi guys.

The other week when we had 'hot temperatures' my loft got up to near 40c with most of my lights still switched on and in fear of them over heating i switched them off.

What is the max temperature a cluster of maybe 5-10 2-5ft Switch Start fluorescent's can take before the temperature gets too high that its deemed to hot 'dangerous' to run them??

A lot of SS fluorescent fittings I've seen state their maximum ambient operating temperature is 25°C so I'd say in that sort of range tops.

I've experienced similar running fittings at the top of a roof space where the temperatures get roasting in the full sun over the summer and the ballasts get blisteringly hot. I usually switch them off when it gets like that as it's just asking for them to burn out or get excessively crispy.

I dunno, I remember in 2016-17 I ordered an angled fitting to o above a cooker in a pub I used to look after that came supplied much to my surprise with a ss choke guess they could take the heat better than HF

I guess the heat will have a faster impact on HF while running SS at higher temperatures will just cause it's overall life to be shorter. You could also use an ultra low loss ballast in those situations they probably wouldn't get any hotter than a normal ballast at room temperature then.

For the fluorescent tubes, the heat is their best friend but for the fluorescent fixtures and the magnetic gear, I'd say they can safely endure the ambient summer temperatures of 25 degrees and over, but I'd do the same you did, Liam, of turning them off just in case

LEDS and HF driven fluorescent fixtures are more prone to heat related problems

It must get pretty hot in the fluorescent sign lights on hot days with the sun beating down on them, given that many of them run 24 hours.

4-6-8 ballasts have quite low dt, and the power dissipation is not much for the size of the light enclosure. The conditions of work of a 36/58/70 fitting are much different

I do remember last year when we had a heat wave one of my 58w fluorescents took out a 3A fuse in the plug, Replaced the fuse and its been fine since..
Since then i've been a bit more weary of running them when the temp in the loft exceeds 36c as i know the temperature under the eves where the lights are must top 55c!!

Only thing I'd say would be to look at the fitting manufacturers literature and check the operational temperature range they state. If your loft is over this, then switch off.

I do remember last year when we had a heat wave one of my 58w fluorescents took out a 3A fuse in the plug, Replaced the fuse and its been fine since..
Since then i've been a bit more weary of running them when the temp in the loft exceeds 36c as i know the temperature under the eves where the lights are must top 55c!!

How odd, you'd have thought if it blew a fuse whatever the fault was would be permanent! Any PFC cap in the fitting?
What state is the ballast in?

I think 55°C is way over the limits most were intended for though, it would be very interesting to temperature probe one of the ballasts after a few hours operating in those conditions, assuming they are just the standard B2 rated ones, the big ultra low loss B1 rated ones would likely fare a bit better in those conditions.