Is it possible to over cool COBs? Liquid cooling

[Hadez411]

Hi all,

I'm scheming up a liquid cooling system with a rad that is outside. It still gets very cold at night. Will my cobs function properly if the coolant gets super cold at night and they are operating with a Tc of like less than 10 celcius?

From the charts I read that the voltage increases as you get colder and the amperage requirement drops. I'm running four 36v (Vero 29D @~1.6a) cobs in series on a 240h-c1750A which is just barely able to make the 36v for each cob (143v is the top of the constant current region). Will it require too much voltage if I chill it too far? Will the colour spectrum remain true?

 

[TEKNIK]

The colour may change a little not a really big deal. You would probably need to try it first to see if the forward voltage is an issue, I doubt that even with cold water running through the heatsink the actual cob will run under 30° it will be more like 50° so long as it has enough voltage to turn it on it will heat up fast. Maybe do a test first in the freezer.

 

[Hadez411]

The colour may change a little not a really big deal. You would probably need to try it first to see if the forward voltage is an issue, I doubt that even with cold water running through the heatsink the actual cob will run under 30° it will be more like 50° so long as it has enough voltage to turn it on it will heat up fast. Maybe do a test first in the freezer.

Freezer, duh!

 

[CobKits]

yes but you definitely have to account for power used pumping coolant around

also compare the cost and time of water cooling to the effect of putting that money at doubling up your cobs to halve the currents, which might be the same cost and more effective lumen bump

 

[Hadez411]

yes but you definitely have to account for power used pumping coolant around

also compare the cost and time of water cooling to the effect of putting that money at doubling up your cobs to halve the currents, which might be the same cost and more effective lumen bump

How low of amperage do you have to go on Vero 29D before a heat sink isn't needed and I can just use a large mass like a U channel or sheet aluminum?

I'm aiming to run at ~1.6a (60w) and 75% of their typical power(79w). If I went down to 40w per cob I'd need to buy different power supplies and 4 more cobs. That's 120$ more for cobs and they'd still need some kinda cooling to stay at a low enough temperature to be more efficient. Compared to buying 8 of thr pin fin heatsinks for 240$ that's good but not compared to a 100$ water system that keeps temps even lower and requires no returning of power supplies.

 

[TEKNIK]

The idea of liquid cooling is to remove heat from inside the room to outside the room, if you want to do it for any other purpose it's not worth the fuck around.

 

[Hadez411]

The idea of liquid cooling is to remove heat from inside the room to outside the room, if you want to do it for any other purpose it's not worth the fuck around.

The idea of it is that it's an excellent thermal conductor and achieves super high cooling efficiency with low tech methods. I'd love to invest in 130mm pin fins but I don't wanna dump 240$ to sit at 50-60C when I could be closer to 35-40C. I know it isnt a huge difference. Luminous output was about 10% different from Tc 85C to Tc 25C. So we're taking about a 5% gain in luminous flux over pin fins if I can keep it fairly cool. No gain over going passive with more cobs though. I should've just waited for the strips to back order :/ would've been cheaper.

 

[TEKNIK]

It's alot of work to do it right. If efficiency is your concern then nichia mid powers are the way to go

 

[Hadez411]

It's alot of work to do it right. If efficiency is your concern then nichia mid powers are the way to go

Efficiency and cost

 

[Hadez411]

It's alot of work to do it right. If efficiency is your concern then nichia mid powers are the way to go

Haven't heard of nichia. Model? Data?

 

[CobKits]

How low of amperage do you have to go on Vero 29D before a heat sink isn't needed and I can just use a large mass like a U channel or sheet aluminum?

I'm aiming to run at ~1.6a (60w) and 75% of their typical power(79w). If I went down to 40w per cob I'd need to buy different power supplies and 4 more cobs. That's 120$ more for cobs and they'd still need some kinda cooling to stay at a low enough temperature to be more efficient. Compared to buying 8 of thr pin fin heatsinks for 240$ that's good but not compared to a 100$ water system that keeps temps even lower and requires no returning of power supplies.

i wouldnt run any cob above 10W on thin aluminum. you need at least somethign 1/8" thick to dissipate well. 3/16-1/4" is better

 

[TEKNIK]

Active cooling works well also, a copper pad helps too

 

[Hadez411]

i wouldnt run any cob above 10W on thin aluminum. you need at least somethign 1/8" thick to dissipate well. 3/16-1/4" is better

Yeah, I've realized this. I made a diy heat pipe thread. My original intent was bxeb strips on sheet metal. Dirt cheap and high efficiency. The sheet aluminum doubles as a fixture/reflector and heat sink. The cost was like 250$ CAD for 240W at around 170 lm/w then bend a roll of sheet aluminum that cost 25$. 275$/240W completed. The meanwell power supplies for those setups were 130$.

These COBs however are either expensive in heat sinks or expensive in the number of them you need to buy.

Six of the vero 29D with no sink, pushing 240w 180 lm/W and a power supply is about 285$CAD for 240w. Then I'd need a thick piece of aluminum, 1/8" thick 4ft long and I'd assume atleast 12" wide, for about another 40$ atleast. That'd be 325$ for 240W.

Currently I have purchased 4 cobs and a power supply to run them for 215$ so I have up to 110$ before it makes more sense to have gone with more cobs at lower amperage. The efficiency at 25c and 1.6a is ~175lm/w but I'll be more like 165 lm/W or less if it's not kept fairly cool. So water cooling seemed neat but it's a lot more stuff to worry about in your grow room.

I guess in conclusion cobs suck and are inevitably expensive or otherwise less efficient. Might as well go with more of them as suggested and see if I can't find a good deal on 1/8" aluminum plate. Maybe smelt a few hundred pop cans in the wood furnace

 

[Hadez411]

i wouldnt run any cob above 10W on thin aluminum. you need at least somethign 1/8" thick to dissipate well. 3/16-1/4" is better

In your experience, what will happen in this situation:

I run 6 vero 29D on an hlg-240h-c1050A. It fits all 6 veros in series at 36v. 119-238V it says.
Makes 37.2W at 1050ma. So when it heats up and the voltage drops, will the light dim because it can't increase the amperage above 1050ma to compensate for loss of voltage? Or is it simply going to start at a higher voltage than what I read it runs at in the "typical use" chart under 1050ma?

 

[Chip Green]

My original intent was bxeb strips on sheet metal.

I've done exactly that....Still have one panel running that way, has been for 2 years....

 

[Hadez411]

I've done exactly that....Still have one panel running that way, has been for 2 years....

Works well? Amperage?
Likes dislikes or new favs?

 

[Chip Green]

With the 190v from an HLG 185H-C1050B- 8 x BXEB Gen1 strips, the entire circuit lost only 1 volt at full temp....Worked enough....Cheap and easy to cut.
I've since rebuilt a few of the 1050ma panels, and run them bare....

 

[TEKNIK]

Your current will stay the same but voltage will adjust

 

[CobKits]

In your experience, what will happen in this situation:

I run 6 vero 29D on an hlg-240h-c1050A. It fits all 6 veros in series at 36v. 119-238V

35.4V x 6 is only 212.4V plenty of overhead, it would just increase voltage towards its 238V max, at which point it would begin to drop the current. i dont think youd get anywhere near the top of driver voltage so it would be 1050 mA x whatever voltage was required at that temperature, in other words, what teknik said...

 

[Airwalker16]

How low of amperage do you have to go on Vero 29D before a heat sink isn't needed and I can just use a large mass like a U channel or sheet aluminum?

I'm aiming to run at ~1.6a (60w) and 75% of their typical power(79w). If I went down to 40w per cob I'd need to buy different power supplies and 4 more cobs. That's 120$ more for cobs and they'd still need some kinda cooling to stay at a low enough temperature to be more efficient. Compared to buying 8 of thr pin fin heatsinks for 240$ that's good but not compared to a 100$ water system that keeps temps even lower and requires no returning of power supplies.

Or run at 30w.. just run 2 parallel strings of 4 in series.