How hot should a led heat sink get?

[mattix]

How hot should they get before the fans turn on? I have a 210 watt led light and four fans to cool it off pretty quickly. I asked this before and one preson said at 150 degrees, any others know when their fans turn on for their leds? before I waste a day checking it with a temp gun and setting up my timer

[Gorgok]

If the noise doesn't bother you or you can slow them down to a point it doesn't it would be better to just cool it constantly (or at least while its on). The cooler LEDs stay the better they perform.

[jedimasterben]

If the noise doesn't bother you or you can slow them down to a point it doesn't it would be better to just cool it constantly (or at least while its on). The cooler LEDs stay the better they perform.

This. If the LEDs are on, I would have the fan running as fast as you can stand the noise. If your fans are noisy, swap them out with something quieter (there are tons of options, but some of the best in the world are Scythe Gentle Typhoons).

[mcgyvr]

The question cannot be answered "properly" without more details.
To be as efficient as possible the fan should come on before LED junction temp rises above the manufacturers recommended junction temperature to achieve the stated lifespan..

[Tek]

I have a similar question. My aluminum L bar is registering 112f with no cooling after 30 minutes. What is the temp to start worrying?

[mcgyvr]

It can take up to 2 hours or more for a LED fixture to achieve "max" temps.
Personally... I wouldn't let any part of the fixture get over 65 deg C. (so measure as close to the LED as possible)
And with LED's "the cooler the better"

but max temp for an LED might be in the 130 deg C (junction temp) (see the LED's datasheet).. If you let it run anywhere close to that though the lifespan is greatly decreased..

[perkint]

As said, cooler is better. The LEDs will put out more light and last longer. I would personally try to keep the heat sink at or below about 60°C, especially when you bear in mind the actual LED junction temp is potentially 20°C above heat sink temp!

Tim