1000 watt 6 or 8 inch duct?

[HGSmiley]

I have a few questions on a design I am doing and need a little advice.
Size of the room is 4 deep, 12 wide 8 high, I will have (3) 1000 watts in a row, should I run 8 inch duct or can I get away with using 6" duct. This will be vented from outside, through to a crawl space and not interact with the grow room air
Other question is how much air do I need to move through the duct to keep them cool?
Thanks in advance,

 

[JJ Bones]

8 inch

 

[HGSmiley]

Thanks, yea thats what I was thinking, do you know how much air I should be moving through the duct?

 

[goathead]

I use an 8" fan. I used 8 inch ducting (rigid pipe) after going through the fan. Before I have a swedge reducer to 6" from 8". the rest or the beginning is now able to go with 6" supplies most grow shops have in stock. Size depends on your temps you are after obtaining. I only have two 1000 watt bulbs on my system and I shoot for really cool. like high 50's, low 60"s. obtain an idea of what you are after then when you start getting there you will know. Be ready to readjust as necessary. it is better to go larger and tape or close off then to go to small and need more and not be able to get it without adding more shit to go wrong. Richie

 

[HGSmiley]

Thanks Richie
My idea is to push cool air from a crawl space through 8” duct, through the air cooled lights (3) 10000 watts, then another 8” inline fan that draws the air and then outside. What I’m trying to do is minimize heat coming from the light without adding more fan then I need. So was wondering what air flow rating, produces maxim efficiency

 

[BeemerBill]

Hey Smiley, You will definitely need 8" and a lot of cfm's. You may even need to run an individual tube to each fixture if you want to control the temp in the room better. I have 6" ducting on one 1000 watt and I run two fans in a 4x4 tent and still can't control the temps or at least it goes up to far for me. As goathead stated it's easier to go down than up. I know I didn't give a lot of info but larger is better.

 

[HGSmiley]

The other thought is to add a ice box at the beginning if it gets too warm, but that would mean adding a chiller too.
Does anyone know what the temp should be, say 10" from glass?

 

[JJ Bones]

I would recommend you get yourself a Can-Fan HO 8" for three lights or something close to it in terms of CFM.

 

[HGSmiley]

After much research and a few suggestions here is my game plan for the lights.
Use a 8” inline can fan with 675 CFM to push cool air from a crawl space through 8” duct, through the air cool lights (3) 10000 watts, then another 8” 675 CFM inline fan pulls the air and pushes it outside.
This sounds like it should work without having to put a icebox on with a chiller, what do you guys think?
And thanks again for your comments. :

 

[goathead]

Run it and be ready to adjust as necessary. Or draw it out on paper then assemble and adjust to your specific needs. Good luck, expect changes . Richie

 

[goathead]

Smiley,I currently getting away with my temps from the winter time still here in central california I have not had to use a ice box or evaporator or any of that yet. The only thing I am lookin into is an ac unit if I go during the summer. undecided! anyway check these pics out for reference hope they give u Ideas and stimulate your creative juices.

good luck, let me know what happens only bad question is the one not asked! Richie