heat issuen with new fan - please help with intake suggestions...

I have a 5x8x10' room (5' is the height) and a 600HPS only. I rencently added a 420CFM 6" fan with charcoal filter to make things cooler and bring in some fresh air for the plants. However, since In have done this my room has gone from a steady 80º to 90º.

When I setup the room I got advice and it semed that having my loosoely fitting sliding doors closed would bring in enough air through cracks and whatnot to keep things cool and bring in C02 - via passive intake. I quickly saw this wasn't working so I cracked open one of the sliding doors about 3" and it helped a little, but things still kept getting hotter.

my grow closet is located in a larger attic bedroom and that room has one real window about 40" away from where the sliding doors are (opposite side of the closet as the fan). So the fan is pushing the air from the closet into the larger room and I think it is then pulling the air from the larger room back into the closet which is why it is getting hotter and hotter.

My thought is this:
Close the closet off but have a one or two 6" intake holes in the door. From those 6" holes, run ducting directly to the window so the fan on the inside will be pulling air directly from the window and less from the recirculated air in the larger room.

God I hope this makes sense to everyone. I am frustrated as hell and have fried half of my starts so far.

attached is a birds-eye view of the setup. NOTE: The fan is actually on the inside of the closet pushing the air out, not on the outside as I have it.

since you have two openings, you're best bet is to run an intake line from the cooler opening and exhaust your hot air out of the hotter opening. This eliminates mixing with your room air. now if your room is cool then take air from there but put the exhaust to the outside, that is most crucial to lower your temps

edit:After looking at the pic better i suggest you put the fan in the grow area, pull air FROM the window, into the grow area via passive, ducted(as to not mingle with hot attic air) intake that is well sealed(seal your "grow closet" well too). Exhaust the air through the small door into unfinished attic. attic grows can be rough, good luck

thanks for the reply. would one 6 " hole be enough? I remember seeing a chart somewhere and it looked like I needed 3 but I can't imagine that would be necessary so I wonder if I may have read the chart wrong..

use your 6" fan as the exhaust and have at least a 7" passive intake. i recommend and 8" intake and still keep a negative pressure.
generally the passive intake shou;d be slightly larger than the exhaust.

^^^what they said ^^^

Take your air from outside mate.

okay, I hooked up a 8" duct to the window near my sliding doors (intake side). I do not have it sealed off yet so I put one of those cheap inline fans for home depot right where the window is and ran the ducting from there to inside of my closet. i had to open one sliding door enough to allow for the 8" ducting -- because of this there is no negative pressure or very little. basically picture a 8"x50" tall opening to the closet with a 8" tube going into it and that's what I have (for now). I have the ducting ending right in the middle of my kiddy pool (see original attachment) and I can feel cool air flowing onto the plants.

the room went from 90º to 88º.


what am I doing wrong? will I be better off completely sealing off the room except for the one 8" hole which is connected to ducting that runs to the window with NO cheap inline fan? do that but keep the fan? should I have (2) 8" holes without any fan?

it looks like you have your exhaust fan drawing out air from near the floor, am i correct in that assumption? if so you need to put it as close to the ceiling or ATLEAST in the middle between the top and bottom. it seems like your pulling all the heat from the top down and drawing out the cool air from the floor level. Another thing is that fans are way more efficent pulling air out rather then pushing.

what are your outside temps? & the temp in the room? I would set the ducting at the top,seal the top 4 feet or so of the gap in the door & use the duct to suck air out of the closet from the top while drawing cool air into the bottom of the closet. if the intake is next to the exhaust,the air will go in& out w/out flowing through the room.your current setup sounds like the fresh air is coming in at the bottom and just flowing out the open door. better to suck the hot air out but your setup of blowing cool air in could work if you sealed the bottom 3+ feet of the door so the cool air comes in at the bottom of the pool and forces out the hotter air at the top.

thanks to all. outside temps are 45º and 75º. the temo in the room is probably near 80º.
I will try moving the fan up to the ceiling, which is only really about 4' off the ground because of the weird shape of the room (pitched roof), but maybe that will help. I will also take the suggestion of moving the ducting to the bottom instead of the top.

I have never really understood the pulling air vs pushing it. the fan is in the room, pulling air and then immediately out of the closet. so it's filter>fan>out.

rbico said:

thanks to all. outside temps are 45º and 75º. the temo in the room is probably near 80º.
I will try moving the fan up to the ceiling, which is only really about 4' off the ground because of the weird shape of the room (pitched roof), but maybe that will help. I will also take the suggestion of moving the ducting to the bottom instead of the top.

I have never really understood the pulling air vs pushing it. the fan is in the room, pulling air and then immediately out of the closet. so it's filter>fan>out.

Click to expand...

fans are just more efficient at pulling vs pushing.

you may need to get a vented hood or a cool tube for your light.

or run your light at night when the temp is cooler.

you want the fan as close to the exhaust hole as possible and have it taking air from the ceiling.

you want the passive intake down low near the floor.

i dont use a filter, so i will let someone else tell you the best location for that.