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Discussion Starter · #1 ·
Good Evening All:

Heat sink temps are at 125F/52C.
Should I run my fans or not.
42 watts of 3 watt LED's on a homemade puck style fixture.
 

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Good Evening All:

Heat sink temps are at 125F/52C.
Should I run my fans or not.
42 watts of 3 watt LED's on a homemade puck style fixture.
Depends on the quality of the diodes..It is almost impossible to guess..
If you are using flee bay diodes I'd say it is too high..but not by much or, not by knowing you will be replacing diodes in a year or so..;)
 

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I would say that's a little high. I would run the fans. They don't necessarily need to be at full power though, you can slow them by giving them a pwm signal or lowering the voltage. I would try to get them to 100F or at least 110, if you want them to last your going to want to keep them cool. Heat is the number one killer of LEDs, hense why usually when they say a led will last 50000 hours they always say that's at a certain temperature of like 35C.
 

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Discussion Starter · #4 ·
Fans are 12 volt and way too noisy at full speed.
Now running @ 4 volts and undetectable.
Test for temps again today.
 

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What does the diode's datasheet say in terms of lifespan vs temperature...there is normally a little graph.

Also when installing PC fans, look for rubber grommets made to mount them without screws. They are designed to help keep PCs quiet.
 

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Discussion Starter · #6 ·
Datasheet says 51C, of course I am @ 52C.
Not all that just 1 degree C.
With all fans @ 4 volts 95F/35C a great improvement with no noise.
Now I'll need to post a thread for this light.
 

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My heat sinks run at 120F max, and have been for almost 5 years. My LEDs are still working fine, but the heat will make the LEDs degrade faster over time.

When I moved my lights to a different tank I accidentally shorted out some of my cool white LEDs (1/3rd of my total LEDs). I bought exact replacements and noticed the brand new LEDs were noticeably brighter and "cooler" color spectrum than the LEDs I was replacing.

Just a matter of if you want the LEDs to last 6 years or 10 years. My LEDs are 3W CREE for what its worth, and I only run them about 5 hours a day full strength with a 2 hours fading up and 2 hours fading down.

Personally I think its worth it to try to keep the temperatures under 100F. I regret cheaping out on my heat sinks, I intend on replacing my whole LED setup in about 2 years when the LEDs are nearing the end of their life.
 
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