Originally Posted by mrhasan (Post 848926)

Try touching the heatsink; I dare you ;)

The thing is, both LEDs and MH "runs" hot but MH "dissipates" heat (and light) omnidirectionally (since its a round bulb) and cannot be fitted with heat sink to take away the heat. On the other hand, LEDs dissipates heat bidirectionally but emits light unidirectionally and so can be fitted with heat sink on the opposite side with heat sink to take away the heat. And hence the "runs cooler" market hype :razz: If some sort of technology comes which allows MH to be fitted with heat, that market tag line is going to be buried.

Originally Posted by Madreefer (Post 849228)

They are not hot at all. Even after running at 100% for hours. I have fixtures with built in fans and other ones without them.

Originally Posted by mrhasan (Post 849232)

Heat sinks are meant to be hot. They taken the heat from the LEDs and dissipate them to the air but not at a rate which makes it run cool (heatsinks have a maximum heat capacity and stays below that or else the heat sink is not the right one for the system). Don't know why yours run cool :neutral: Probably you are using oversized heat sink?

Originally Posted by sphelps (Post 849234)

Ahhh..... wrong :lol:

LEDs produce a large amount of heat per area which can seem high because of there size but overall is very little. The junction temperature (between LED and heat sink) needs to be kept relatively cool to insure the LEDs don't overheat, in order to do this the heat sink has to be large enough and kept cool enough to maintain allowable LED temperatures. The cooler the heatsink the better the LEDs work and the longer they last. Most heat sinks probably run around 25°C.

Originally Posted by mrhasan (Post 849232)

Heat sinks are meant to be hot. They taken the heat from the LEDs and dissipate them to the air but not at a rate which makes it run cool (heatsinks have a maximum heat capacity and stays below that or else the heat sink is not the right one for the system). Don't know why yours run cool :neutral: Probably you are using oversized heat sink?

Originally Posted by mrhasan (Post 849236)

Is the number that low? I remember burning myself by touching the heatsink of a DC PSU. I am sure the heat sink doesn't run boiling hot but still 25 is much more lower than what I thought (my guess was around 50-60 :razz:)

Originally Posted by Madreefer (Post 849237)

No just what my fixtures come with.
I've had or still own: Sol Blues, Sol Hydras, Zetlight and Ecoexotic Panorama Pros.
I know how heat sinks work so no explanation needed. Speaking from actual experience rather than something i've read.:biggrin:

Originally Posted by sphelps (Post 849243)

Obviously the operating temperature will vary for different devices, not sure why you would compare LED temperatures requirements to that of a power supply.

Originally Posted by kien (Post 849254)

Forget the heat sinks! Steve, tell us what you think about the hybrid LED+T5 fixtures.

Originally Posted by sphelps (Post 849255)

no comment