Lighting Cob vs hps

[Rusty_Shackleford]

If you had 2 similar heatsinks then yes the one with a fan would be cooler. But most active heatsinks are not similar size. They generally are smaller and situations like this happen. Noise,cost and operating cost add up too when you have multiple fans humming along.

As for the lifespan I still haven't seen anyone burn out a cob under normal operation. Never heard about it either. What the cobs are rated for and what we typically run them at are well below danger zone. There is also less heat generated from a passively cooled than an actively cooled too.

Sorry rusty I wasn't picking on you directly just the setup. Most people aren't educated enough and things like this happen. Trying to make a point, not put you down.

No problem Smo, I didn't take it like that at all. I actually suggested OP go passive due to the increased chance of failure on the active cooling. I was posting the picture more as a beware of active cooling lol. With active you have each individual fan, and the psu. A failure in one or the other and in the words of aspen ski instructor, your gonna have a bad time. If you still want active go passive and add active, give yourself a safety net

 

[BigSm0]

I was typing that last part out but realized it was a waste. But exactly how it should be done if someone were to go active. If the fan dies the cob will still survive, or WHEN the fan dies more importantly. Extra drivers, wiring, fan cost, energy consumption, and noise is enough for me. a fan in the tent or room is enough to cut heatsink temps drastically without going through all that mess.

 

[Rusty_Shackleford]

I was typing that last part out but realized it was a waste. But exactly how it should be done if someone were to go active. If the fan dies the cob will still survive, or WHEN the fan dies more importantly. Extra drivers, wiring, fan cost, energy consumption, and noise is enough for me. a fan in the tent or room is enough to cut heatsink temps drastically without going through all that mess.

I agree completely. And when the fan is gonna die is right. Most them are made for computers which arent supposed to run 18+ hours a day yet alone everyday for the same life span as a cob. Me myself, I'm probably gonna keep fans on top of the pin heatsinks, but that's just because I already have made the wiring harness for these lol

 

[KonopCh]

In sealed tent you don't hear noise from a small 8cm fan. 10 fans is only 20W more and I doubt here on forum 10% have more than 10 heatsinks. And that's 10 bucks per year for electricy of fans! You can also make 1m heatsink bar and have only one fan on them, like I do. You don't need flexibility if you train your plants. That way you also don't get that much fluffy buds compared with "let it grow" plants.

Maybe I shoud add word "estimated" lifespan, which is shorter with COB which has Tj 80°C (passive cooling), compared to COB which has Tj of 30°C (active cooling).

Also you bump efficiency for around 5% with active cooling.

And you guys have computers with CPU. How many of you actually upgrade your cooling fans in your computer? Maybe every 7 years one fan. And fan is 5 bucks.

 

[BigSm0]

Then the fan dies on a paralell configuration and you lose the whole lot. One fan is quiet, 4-8 fans is not. Wiring, driver consumption, fan cost, fan consumption, driver cost, time to install them. No one in their right mind would add fans vs a larger heatsink. Unless it's a prebuilt manufactured light which has its own reasons for going active. There is also no way that estimate of a50c-120f difference is accurate when my typical heatsink temps are below that. I am not picking on your light but Passive is the best and safest option without debate.

My 8 cob light would need 8 5watt fans. 40 watts, 160btu of heat, 40 dollars for fans and 15 dollars for the driver. Probably 2 hours to install. All that cost and energy I could have had a 9th cob and broke even.

You also train your plants to suit your light. Most do not. That's why there are guides on how to lst a plant. Most don't even know what or why nevermind how. The more you do and the safer it is the better. Eliminating risks and failure points. Kiss

 

[Penrey]

I think the passive style is deff the way to go as long as you stay well within the ratted heat watts. I went with 140mm pin style that is rated at 85 heat watts I think, and I am running my cob at 50w. I can literally hold my heat sinks and they are barely warm to the touch. The cree cobs I am running at 1.4 are putting out like 35% of the watts used as heat, so under 20 watts of heat on a HS rated at 85.

 

[Penrey]

In sealed tent you don't hear noise from a small 8cm fan. 10 fans is only 20W more and I doubt here on forum 10% have more than 10 heatsinks. And that's 10 bucks per year for electricy of fans! You can also make 1m heatsink bar and have only one fan on them, like I do. You don't need flexibility if you train your plants. That way you also don't get that much fluffy buds compared with "let it grow" plants.

Maybe I shoud add word "estimated" lifespan, which is shorter with COB which has Tj 80°C (passive cooling), compared to COB which has Tj of 30°C (active cooling).

Also you bump efficiency for around 5% with active cooling.

And you guys have computers with CPU. How many of you actually upgrade your cooling fans in your computer? Maybe every 7 years one fan. And fan is 5 bucks.

Cree lists the l80 lifespan at 85c in the 16k hour test to 57.4k hours. That is 2391 days. Running passive cooling and getting 80% of original output for 6 and a half years at 24/7 up time is ok with me. I will be on to the next tech by them.
As for me upgrading the cooling for my pc? I run a haf case with a cm d92 cooler. I never replace my fans. Once a year b4 summer I peel the sticker off my fans revealing the rubber plug. I remove that, the retaining clip and oil both bearings. I have 0 issues with their performance and have been doing this for like 10 years with this case.

 

[Jimmyclone]

Are we having this conversation again? 200w of quality cobs will beat a 400w hps.. No problem.. The wider spectrum coverage, and wider spread of photons will win everytime..
Do it bud.. I will never go back to hps... EVER..
Cheers

 

[wwwillie]

Wow love how this thread wandered. Lot's of good info and a fine argument for passive cooling. Especially for DIY. KISS is a fine engineering standard I try to strive for. As to what grow what or is equivalent to who. It's a matter of fact and opinion and opinions about facts. You know what I say? Try it you'll like it!!

 

[BigSm0]

Just entered IG and there was a guy saying to ditch the cobs and go with hps. Wwwillie is correct. Opinions are like..... lol no it's 100% true. The best way to know is to try it.

Pop did mention reflector losses but that's deeper than you may realize. Cobs are single sided. Hps is not. Even if the bulb is 4" away from the top of the reflector it needs to travel 4" up and 4" down. When it travels up and down it's not on a straight path either. That may sound minimal but that loss is much higher than we think. Another thing is consider your space. As mentioned above about cob placement and coverage, if you were to use a 4x4 tent for example as they are very common consider the hps coverage area. That center hot spot from hps and drop off on the edges also makes up for significant losses on the entire canopy. A 4x4 tent is 16sq'. The outer 1' perimeter is 12sq' making the center just 4sq'. Even if you were to use 6" of the outer edge that's 6sq' of a 16sq' tent. When you can place cobs more evenly across the canopy these outer edges are not so neglected.