Exhaust fan sizing

[Lowdog]

Im looking at setting up a 4x4x5.5 ft tent in a room with a window a/c in it and using a 1000w light. The light is in a closed, vented hood with 3 4" duct openings. What cfm fan should I use. I'd like to pull air from the tent, thru the light, and run about 10 ft to discharge.

 

[JJ Bones]

Something like a 4" Can-Fan would likely work well for your space.

 

[Lowdog]

Thanks, JJ. I have been trying to find a chart or article on ex. fans and cant find anything useful. I do HVAC work and understand the problem, Just don't know where to find the answer. I would think that the size of the space and the amount of heat gain from lights etc would determine how much air (cfm) has to be moved to maintain the required temp. Do you know where I might find this info?
Thanks

Lowdog

 

[JJ Bones]

Some people will say to replace the air every minute, others say every five minutes.

I tend to do the every minute method, give or take. So your space is 88 cubic feet. I was recommending the Can-Fan which is 155 CFM so that should be plenty powerful. Consider corners and ducting+fixtures can lower the CFM simply because of the resistance (which I'm sure you're already well aware given your job).

Also you can purchase a fan speed controller to slow down the fan if it was too strong, or speed it up. I like fans that are a little extra in case of those really hot days.

Here is a reference from this forum: How Much Ventilation Do I Need in My Grow Room?

 

[Lowdog]

I got some good info out of that. The other thing I cant find if the right size fan for an enclosed light. One where the fan pulls air thru the light but not from the grow space, solely to cool the light. What size for 1000 watts?
Thanks, man.