Cool hood Ventilation question (fan size)

Hi
I'm in the beginning stages of constructing a grow room for my house, I have a question if anyone can help

I'm wanting to use two 1000w hps and a 600 hps all with cool hoods ducted in a closed loop series (about 12 -15 feet in length) and then the dry vented air pushed into another room so I can use this heat for my home..

I'll be pushing air from outside through the fan then lights in a straight line, one 90 degree up and then its vented.

I've read that through each 1000w the temp will increase 6-7 degrees, after the 2nd 1000w it may be 33 degrees c headed into the 600w...

1) is this okay? To feed 33c air to a 600w to cool it?

2) what size fan should be used to cool 3 lights in series? About 15 feet of ducting

Right now I have a 6" fan 400+ cfm (i cant exactly remember the number if its 435 or 485) and a cool hood with 6" flanges, I could buy or make a 8" to 6" reducer if needed... or a more powerful 6" fan

Hope my question is worded properly, ty very much for any opinions or suggestions

I think your misunderstanding what air cooled lights are for. They are not so much about cooling the bulb, its about removing the heat the bulb creates from your room.
It works far better allowing cool air into your room, making the whole grow room cooler and then pulling/pushing air through your lights which heats up as it passes over the bulbs.
The bulbs run very hot, if the air is 20 degrees or 40 degrees passing over it makes no difference to the bulb itself.
Its different if your running a sealed room because then the air must be pulled from outside the room and pushed outside the room.

Hope that makes sense.

coreywebster said:

I think your misunderstanding what air cooled lights are for. They are not so much about cooling the bulb, its about removing the heat the bulb creates from your room.
It works far better allowing cool air into your room, making the whole grow room cooler and then pulling/pushing air through your lights which heats up as it passes over the bulbs.
The bulbs run very hot, if the air is 20 degrees or 40 degrees passing over it makes no difference to the bulb itself.
Its different if your running a sealed room because then the air must be pulled from outside the room and pushed outside the room.

Hope that makes sense.

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What he described is just a sealed room set up. The bulbs are getting cooled by completely separate air rather than pulling hot air from inside the room already. What he describes is really a pretty ideal set up to maximize the cooling of the lights. The better all that cooling works, the less heat gets emitted into the room. Obviously, the room itself will need its own ventilation to ensure CO2 exchange and temp control. But with the lights vented seperately, he will be in an ideal position to seal the room with CO2 and AC for a perfect environment.

You don't want to over cool the lights, they are designed to run at certain temps, and changing that will effect the spectrum and longevity of the lights. I don't know what is recommended officially. I have a 500ish cfm fan cooling my 1k hps. It works well I think, I can touch the top of my reflector without issue. That would make me want to suggest that you should have 1000-1500 cfm to properly move the heat through the system you are talking about.

Cheers @Thundercat , good point, yeah he just didn't mention the co2 addition. I agree though it would be ideal if that's what his plan is.

One 6" inline fan is more than enough to remove heat from those 3 cool hoods. Even running it at half speed would be enough and 33C is ice cold compared to the temps the bulbs produce.

You're not looking to cool the bulbs themselves but just to remove excess heat from the room and you don't need hurricane force winds to do that.

Ah yes... I plan to use co2
Alright ty very much for your comments and opinions

For now, for my planning, I'll continue to use the 6" I have to cool the hoods

Hopefully in a few months I'll have some pictures

Thanks again

Edit: I never thought about freezing outside winter cold hitting the bulbs and reducing their potential or even break them . maybe I'll build in a summer outside vent and push air from another room for cooling in winter, something I'll have to consider

WH33LS said:

Edit: I never thought about freezing outside winter cold hitting the bulbs and reducing their potential or even break them . maybe I'll build in a summer outside vent and push air from another room for cooling in winter, something I'll have to consider

Click to expand...

That's not a concern really. You would have to splash water onto a hot bulb to break it. HID bulbs are used in all sorts of outdoor applications in all sorts of weather and it doesn't hurt them none.

I used to draw my room air in from outside but that was a bugger to deal with. Up to +35C in the summer and down to -35 in the winter in northern Alberta here. Very hard to keep the room's environment in balance. The grow room takes up about a fifth of the basement so years back I rigged it up to draw all the air from the greater area of the basement. Much better as the temps down there only fluctuate from about +5C - +17/ 40 - 65F.

Good point, I'll consider doing the same to eliminate those temperature fluctuations

Maybe I'll also place a 2nd dehumidifier in the room that I draw air from to help keep the humidity down

Ty