need help with 2 400w CMH's in closet grow setup

[Toob]

hey guys, just ordered 2x 400w hps ballast, phillips retro white cmh bulbs, and super sun reflectors. searching and these forums has been so helpful already but I just had a few questions regarding my grow setup.

My grow space is a closet 5 ft wide x 2ft deep x 8ft tall. My plan is to use the space in-between the bottom of the closet doors and the floor as a passive intake then exhaust with a 250 cfm fan through the ceiling into the attic. I plan on also using the DIY simple scrubber for odor control.

Temps: do you think my exhaust system alone will be able to keep the temps down while the 2 400w CMH's are on?

Smell: If we vent into the attic will units connected to us potentially smell it?

Size of intake/exhaust: Right now the gap between the doors and the floor equates to an area of 4ftsqd, making my goal exhaust sizes area to be 2ftsqd. Does this seem large enough?



toob

 

[Cannabean]

hey guys, just ordered 2x 400w hps ballast, phillips retro white cmh bulbs, and super sun reflectors. searching and these forums has been so helpful already but I just had a few questions regarding my grow setup.

Welcome Toob. I run a similar setup as you propose. I suggest getting hps bulbs for flowering also. CMH are some of the best bulbs for veg though so you have some time.
I also suggest researching a ScrOG setup too. 400w bulbs don't have the best penitration and keeping the canopy even and close to the bulbs will help in that respect.

My grow space is a closet 5 ft wide x 2ft deep x 8ft tall. My plan is to use the space in-between the bottom of the closet doors and the floor as a passive intake then exhaust with a 250 cfm fan through the ceiling into the attic. I plan on also using the DIY simple scrubber for odor control.

My canopy space is 2'6" x 4' and 8' tall but I ventilate a 4'x8'x8' closet so I use a larger (470cfm) exhaust fan. A carbon scrubber will add resistance and drop the effictive cfm of your fan but you are lookin at 80 sq ft. 250cfm/ 80cf >3 min where 3-5 is ideal. I'm no expert at hvac though, hopefully others chime in.

Temps: do you think my exhaust system alone will be able to keep the temps down while the 2 400w CMH's are on?

250cfm will be adequet to keep 800w properly ducted cool. Will it exhaust the room frequently enough, I'm not entirely sure.

Smell: If we vent into the attic will units connected to us potentially smell it?

Size of intake/exhaust: Right now the gap between the doors and the floor equates to an area of 4ftsqd, making my goal exhaust sizes area to be 2ftsqd. Does this seem large enough?

Make sure that whatever intake you decide to use to make it lightproof, under door intakes complicate this sometimes.

 

[FreezerBoy]

Got your abacus handy? fan-intake calculator

 

[green_grow]

i am wondering about your math . you say that you have 4sq.ft. of intake below the closet doors ... this would mean that on your 5' wide closet you have a gap of almost 10" between the doors and the floor ???
(4sq.ft. is a far bigger intake area than you will need, by the way.)

also, any gap at all will allow the eerie-looking HID light to shine though. if you need the grow to be stealthy, you will have to light-proof it.

 

[Toob]

Oh yeah, i'm definitely going to need a breathable cover over the cracks thanks.

i am wondering about your math . you say that you have 4sq.ft. of intake below the closet doors ... this would mean that on your 5' wide closet you have a gap of almost 10" between the doors and the floor ???
(4sq.ft. is a far bigger intake area than you will need, by the way.)

also, any gap at all will allow the eerie-looking HID light to shine though. if you need the grow to be stealthy, you will have to light-proof it.

oh damn you're right my math was totally wrong. the area of my passive intake would be ~19inchsqd. and using the vent size calculator i'll need 123 inchsqd =X. Just gotta trim off some wood now.