Lighting Heatsink Help Please

[KAVO]

Hello folks

A little help with heatsink guys,I have a Mecha Tronix star heatsink rated 57w up to 7300lm, I want to run one 36v cluo 1212 4000k 153lm/w at 1.4amp. When I do the math 36v by 1.4= 50.4w this is Ok but 153lm by 50.4w = 7711.2lm.So can I run with this or need a bigger heatsink.Any help would be great trying to build a little veg light. Thanks guys

 

[BigSm0]

Hello folks

A little help with heatsink guys,I have a Mecha Tronix star heatsink rated 57w up to 7300lm, I want to run one 36v cluo 1212 4000k 153lm/w at 1.4amp. When I do the math 36v by 1.4= 50.4w this is Ok but 153lm by 50.4w = 7711.2lm.So can I run with this or need a bigger heatsink.Any help would be great trying to build a little veg light. Thanks guys

Yes that will work perfectly. They do get warm but with any sort of air movement in the room it runs much cooler

 

[thetreeman]

You need to understand they are rated by how many heat watts they will dissipate, not how many watts the cob will use. So if you are running a cob at 100 watts that is 50% efficient, that means it will put out 50 watts of heat and 50 watts of light. Your cob is only using 50 w total, so even if you figure it may be running 40% efficient, it would only be producing 30 watts of heat, about half what the heatsink is rated for.

 

[KAVO]

Thanks guy's for the help, and what a simple but brilliant explanation from Thetreeman.Off to build a little veg little now then hopefully can get some photos and I did a Mars 300 diy conversion a while back thanks to great help from BigSm0 and this brilliant forum, thanks again folks

 

[BigSm0]

You need to understand they are rated by how many heat watts they will dissipate, not how many watts the cob will use. So if you are running a cob at 100 watts that is 50% efficient, that means it will put out 50 watts of heat and 50 watts of light. Your cob

. Yes and no. There should be less heat at the heatsink with a more efficient cob but each watt produces the same amount of heat regardless of efficiency. There are a lot of factors that go into proper heatsink sizing including ambient temperature and air flow. The basic wattage claim the manufacturer posts is most likely not under the same conditions as you may have. Ideal watttage and maximum wattage are also factors to understand. I will say I use them myself kavo and with adequate air flow they hardly hit 100 degrees.

 

[thetreeman]

. each watt produces the same amount of heat regardless of efficiency.

A watt is a measurement of energy which in this application will be converted into heat and light. A 30% efficient cob driven at 100 watts will produce 30 watts of light and 70 watts of heat. Drive a different cob at 100 watts that is 50 % efficient will give you equal amounts of light and heat. Your heatsink only cares about the heat portion as the light doesnt affect it. In an enclosed space, all light turns into heat eventually but, other than working to raise the ambient temperature of the room, it doesnt affect the heatsink directly. A heatsink that is rated at 50 watts is being rated to dissipate 50 watts of heat in laboratory conditions, if you are using 50% efficient cobs driven at 100 watts, this 'should' be fine. I typically dont drive my heatsinks more than 70% of their rated dissipation capacity, because you will loose some efficiency as the temps increase and it will also affect lumen maintenance and cob life. You are using a heatsink thats rated for 57 watts so if you figure 70% of that is 39.9 watts and say you are using a cob that is 40% efficient, you should be able to drive it with about 66.5 watts and still have an adequate safety margin.