Air-cooled hood...can you pull too much air through?

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Originally Posted by EvilCartman

If properly set up, there is no heat issue at all. I think that bit of popular info has its roots in folks who didn't really understand their airflow requirements. With the passage of time it seems as though it has become accepted as a fact.

The air temp rise from a single 1000HPS with good airflow will be on the order of about 4 degrees F. I've set up banks of lights in series of 6 with a single 8" fan, outlet temps were under 100F with an inlet temp of 70-75F. Any diminished longevity is negligible, unless temps get a good bit higher.

The bulb itself is in the neighborhood of 200F, so with inadequate flow things *will* go south quickly! :detective1:

Not jumping on you, Senorx! Just thought I'd throw this out there. I've seen it posted many times and it's really not a problem. HVAC/R for a couple decades taught me a thing or two. ;)

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Are you talking about the rise in temp of the cooling air, or in the room in general?

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Originally Posted by senorx12562

Are you talking about the rise in temp of the cooling air, or in the room in general?

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Yes, just the lamp cooling air as a separate system. Drawing & exhausting outside of the grow environment.

Reading this gives me cause for concern.
I've got 3 enclosed 400wt hps lamps all being cooled by a 4" ActiveAir doing 165cfm. The glass on the hoods gets too hot to touch if feeling directly under the lamp. They're moderately warm as you span out from center. Is this too hot?

So is my 165cfm under power for cooling 3 lamps?

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Originally Posted by RoundEye

Reading this gives me cause for concern.
I've got 3 enclosed 400wt hps lamps all being cooled by a 4" ActiveAir doing 165cfm. The glass on the hoods gets too hot to touch if feeling directly under the lamp. They're moderately warm as you span out from center. Is this too hot?

So is my 165cfm under power for cooling 3 lamps?

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The glass should be hot. Is the space too hot for the plants? You should have the plants about 8-12" from a cooled bank of 400s. You should be fine in the winter at lower cfms.

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Originally Posted by RoundEye

I've got 3 enclosed 400wt hps lamps all being cooled by a 4" ActiveAir doing 165cfm. The glass on the hoods gets too hot to touch if feeling directly under the lamp. They're moderately warm as you span out from center. Is this too hot?

So is my 165cfm under power for cooling 3 lamps?

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If it's working for your space, then I wouldn't worry too much. If the plants are happy, run with it.

But, IMO that blower is borderline *at best*. Depending on the number of bends and the length and type of ducting, you're moving significantly less than the rated flow. Check the seal of the reflectors, any leaks are reducing useful airflow. The glass should not be "too hot to touch" anywhere.

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Originally Posted by EvilCartman

Yes, just the lamp cooling air as a separate system. Drawing & exhausting outside of the grow environment.

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Good to know. Thank you.

hey cartman, you seen very knowledgeable about HVAC systems and they have been giving me fits the past couple weeks trying to figure my new ventillation system out...

I am upgrading my medical grow and have some questions on my new design.

I am planning on having 3 rows with each row having 9 1000w XXXL air cooled reflectors. each row will be 4ft wide and 36ft long. There will be a space of 3ft between each row so that the plants are each to access. I live in the north west USA so during the summers it can get up to 100 and the winters get down below zero at times. I am planning on having the intake for my lights to be pulling air from the crawl space and exhausting it outside or back into the house during the winter to help with heating. I'm sure that pulling air from the crawl space (which is 4ft tall with 1360 square feet) I will need to have an intake fan for the crawl space/basement to help create a positive pressure. I will also be pulling air across the lights compared to pushing it since it is more efficient.

My Questions:
How many reflectors can I hook up in a row? I can't imagine I could hook up all 9 in a row with each flowing into each other cause after the 2nd or 3rd light wouldn't the air be so hot it wouldn't be cooling the lights?

What size fan will I need to use to cool the lights? I've read that I should have around 250-350cfm per light but is that right?

I know that the 6" hoods allow for more light to be reflected to the plants but the 8" would give me better air flow. so which should i eventually decide on?


would this work? have my intake be 30x30 box ducting coming from crawl space, then split into 3 14" intake trunks that run the length of my rows. (I will also have to hook up a 6" or 8" to the main intake for my 4 lights in the veg). Each HPS light will have 6" or 8" flex insulated tubing (i could probably do 6" if i'm doing this method) coming from the intake 14" trunk to the HPS light then to the 14" insulated exhaust trunk for each row of lights then at the end of each exhaust row trunk I could have a 14" canfan 1823cfm fan ($520) or 14" vortex fan 2900cfm ($1000). Each insulated exhaust trunk would directly connect after the fan run into a 20x20 insulted box duct that runs into the attic. does this sound like the best way to run the system? i've done by homework but i cant find a ton of information on this topic or maybe i've just been looking in the wrong spot ha!

if you really want to get crazy look into this Hydrogen 6 Inch Ice Box Water Cooled Heat Exchanger - Plantlighting Hydroponics

I have 8- 1000w hps lights connected with 2- 700 cfm fans and one of these every other light tubed back to 2 - 100 gallon reservoirs with a 1 hp chiller. I also run the hydrogen co2 water cooled burner in the same fashion. My room never gets above 85 degrees with everything running at max and no supplemental ac. These things work very well