CFM per 1000W HID Light

[HighWaterMark]

I'm building a "perfect" sealed CEA grow op. The flowering room will have a 250ft² footprint (10'x25') with 8' ceilings. It will have two rows of 4 air-cooled 8" vented hoods (inline - 1000W HPS lights) with the air coming from and exiting to somewhere else (lung - topic for another thread). Safe to say the air is not coming from or returning to the flowering room. Of course, the air is being moved by an 8" inline fan. Other consideration:

1) room is CO² enhanced.
2) room is temperature and humidity controlled.
3) room is light-cycle controlled
4) media is soil-less and room will be antiseptic as is reasonable
5) A/C is likely ductless mini split and particulate matter will be reduced by a separate Activated Carbon Filter

Given the above 5 considerations, what's a good rule of thumb for the 8" inline fan's CFM to properly cool my line of four hooded 1000W lights? Do those experienced in sealed grow rooms think in terms of CFM/1000W light regardless or in terms of increased resistance, heat and finally, increased air flow needs of four hooded lights in a ducted line?

Last question - re increased vs decreased air pressure in each hooded lighting assembly, do y'all prefer to push or pull the air (respectively) with the inline fan?

 

[trichomes]

need to know what the temp. of the air is, that you are pushing? or pulling? across the bulb/s. also, how many bulbs will each fan be cooling? lemme know, I'll have better answer w/ this info, GREAT SETUP!!!!

 

[HighWaterMark]

Thanks for replying and thanks for the words of encouragement. I've spent a while thinking this one through.

1. the air cruising across the bulbs will start out at 65-70F. It's a tad bit NNE of Santa Barbara sort of tucked against the Santa Ynez Mts. (where summers are hot) , so we'll need to do a cost analysis as the first summer grow is drying/curing. It may be cost prohibitive to have an air chamber @ 65F.
2. each 8" fan will be cooling four 1000W hooded/vented lights, connected inline with insulated ducting. Good question - I worry if I'm pushing it with four HPS lights.

 

[HighWaterMark]

I don't know if this has anything to do with anything else, but heard of folks getting into humidity troubles if there's a big temperature difference between adjacent rooms or temperature flux between day and night. I don't want to work the dickens out of my dehumidifier. Again, $ wasted.

Plus, I want to get all this stuff dialed in before I crank on the carbon dioxide so that I'm not chasing my tail.

 

[trichomes]

Inline extraction fans are commonly designed to be positioned close to exit vents so that they extract (or suck) air from a room. However, when used as part of an air-cooled lighting system, it's preferable to push air over your lamps that is, your inline fan is positioned before your air-cooled reflectors. Not only does blowing cool air create less wear and tear on your fan's motor than sucking warm air all the while, but you will enjoy more control over air movement in and around your garden. Blowing creates a positive pressure inside your air-cooled lighting ventilation system. If there are any leaks then air will spill into your garden and be dealt with by your garden's ventilation system. Pulling, on the other hand, creates a negative pressure inside your air-cooled lighting ventilation system, so any leaks will draw your garden's unfiltered air in.

 

[trichomes]

You shouldn't link up more than four 8" reflectors. Use an infra-red thermometer to monitor the surface temperature of your plant canopy leaves (closest to the grow lamp) - the temp. should not read above 82. For maximum cooling efficiency, bring in one mainline cool air duct and use Y-pieces and ducting serve each light individually.

 

[HighWaterMark]

Again, thanks. I knew from physics ten-thousand moons ago that I would have air pressure issues and nothing keeps a perfect seal forever. Nothing. Your answer put it into a sensible perspective. So you know, if I can follow my 5-year plan this actually is will become a commercial medicinal grow. It's my forte. I don't mind spending the money for the best end-product but I hate wasting it.

 

[HighWaterMark]

What's your advice on the mouth-diameter of the mainline before it forks into a Y? And do you advise two fans, one for each line after they straighten out? And finally, what's your thought on CFM for each?

Back to the flip-flop concept of the central room, or "lung". I promised to save it for another thread, but the time just feels right. How does it work unless you are working on a 30 hour day? Unless I'm misunderstanding something, you are flowering in one room (12/12) and vegging in another (18/6) using 4 ballasts for 8 lights. 12 + 18 = 30. Like much of the ancillary equipment, your ballasts are in the central of your 3 rooms, or your "lung". Back to the timing. If your flip-flop relay activates the ballasts so that your running half as many (4) as you would normally (8 in the two lateral rooms to service your 8 lights), you need some form of a 30hr day to accommodate 12hrs on, (flip) 18 hrs on, (flip) 12 hrs on, (flip) 18 hrs on, etc.

What am I missing?

 

[trichomes]

recommend to push the air through your air cooled lights to avoid overheating your fan and to create a positive air pressure in your ducting and light hoods.

Approximately 150 - 200 CFM is required to air cool a 1000W Bulb. this is from what Ive read, never confirmed numbers, hope it helps, sounds about right for your application, I'd double it. Also it's worth it to pay xtra for quality smooth/quiet blowers.

 

[HighWaterMark]

Thanks trichomes. Back to the chalkboard.

If I'm understanding you correctly, 300-400 CFM is 1200-1600 CFM per 4-light line or 2400-3200 CFM if the source of air movement is before they joint of the first Y. Goodness, I'm going to have to borrow the wind tunnel at the Army's place outside of Raeford, NC. I'm sure they won't mind.