Blow hot air out or suck cold air in?

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poopstain2

Member
As of now I'm sucking warm air out of a small room and passing it through my 2- 1000watt hoods. The small room is warm because it contains 2- 1000w ballasts 1- 400w ballast and 400w MH blub powering a small veg tent and a 5.5amp diy water chiller. Avg temp of this room is 78-82. Root zone is a steady 62F.

I exhaust this hot air straight out the house. The warm air of the said small room that I exhaust outside is replaced by air from the first floor thru a 12x12" vent. The first floor has a avg temp of 79F due to other non weed related conditions. In the summer 2 14k btu AC's to keep the first floor down to around 70F. I can't open windows due to security concerns.

I'm not crazy about blowing pretty warm air (compared to the temperature outside) out of my house 24hr's a day. What do you guys think is a good avg outside temperature so I can suck cold outside air past the 2-1000 bulbs and still cool a room with the ballasts chiller and veg tent? I know I can test it myself but fan is mounted and taped really nicely and I don't think an avg of 52F is cold enough yet. I assume at a cool enough outside temp I can run my room 100% sealed. As of now I have my co2 controller set to suck the hottest lowest co2 content air from the ceiling of my grow area.
 
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poopstain2

Member
The question is when is it better to suck cold air into my house then blow hot air out of my house? if I pass 52F air pass my 2 1000watt bulbs will the air be 75F or cooler?
 
bwest

bwest

Well-Known Member
My 2 cents. I would rather blow warm air out than suck cool air in. My thinking is that it could lead to a humidity problem. But, I also know nothing about your setup other than the layout you mentioned. Depending on where you lived maybe. I lived in Georgia, and even at night in the summer that air can be nasty warm and humid. And if your introducing already humid air into a grow room, it could be a bit much.
 
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poopstain2

Member
Thanks for the replies guys! The humidity is really low here in the winter months. Added to the fact that that air wouldn't be entering the grow space(only thru the hoods), just the equipment room with the veg tent. I'm at 27% RH in there right now, I could use a little boost.

What I'm really looking for is someone with experience of passing cold air over 2400+ watt bulbs and what temperature the air is when it gets the end of the ducting. Also will passing cold air past the bulb cut down significantly on radiant heat.
 
bird mcbride

bird mcbride

Well-Known Member
When I do ventilation I like to keep the pressure in my grow at 15lbs per square inch. I don't use a sealed hood for my hps. The reason that I do this is because nitrogen will disipitate faster at lower amospheric pressure than it does at sea level. Most fert companies do thier dosage level at sea level. So if people see a burn in thier negative pressure grow-ops, this is the reason. I prefer to keep my intake and exhaust balanced. When you start drawing air in from outside to cool your hood vapour will build up and cause condensation to drip off the vent pipes when hooked straight through the cool tube etc. Pretty much all new houses since the ninties have positive air exchange built in to the heating and cooling systems and there is always a cloud of vapour coming from the out vent in these new houses. When the temp gets to -50f outside I simply slow down my blowers to cut back on any drips resulting from condensation.
 
alcohol

alcohol

Active Member
of course passing super cold air through your hoods is going to reduce the radiant heat greatly. I think you will experience a lot of condensation buildup as MCBRIDE stated. Super cold air inside your hood in contact with warm room air = H2O buildup on the warm-sided surface.

If you are trying to cool 2400w inline, that is not going to work to well.

Ps. i dislike air cooled hoods.
 
JonnyAppleSeed420

JonnyAppleSeed420

New Member
poopstain2 said:
The question is when is it better to suck cold air into my house then blow hot air out of my house? if I pass 52F air pass my 2 1000watt bulbs will the air be 75F or cooler?
Click to expand...
That is a question only you can determine. The colder the air across your lamps the cooler it will be, but not much. Remember, your bulb is running a temp of 400-500 degrees so a difference of 10 or even 20 degrees of the air passing by, will result in similar cooling affect. You will be way more efficient pulling the hot air out and having a passive intake. If your room still is warm use another inline fan for your intake at the floor. Matching the cfm's on the two fans is recommended but if your exhaust is larger then make sure it still can draw air if the intake fan can't keep up....JAS
 
NorthofEngland

NorthofEngland

Well-Known Member
alcohol said:
of course passing super cold air through your hoods is going to reduce the radiant heat greatly. I think you will experience a lot of condensation buildup as MCBRIDE stated. Super cold air inside your hood in contact with warm room air = H2O buildup on the warm-sided surface.

If you are trying to cool 2400w inline, that is not going to work to well.

Ps. i dislike air cooled hoods.
Click to expand...
Why do you dislike air cooled hoods?
 
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poopstain2

Member
alcohol said:
Why are you supplementing CO2 in a non sealed room?
Click to expand...

My 20lb can last 6 days @ 1500ppm if I can stay out of the room and not open the door. The radiant heat is handled buy a 6" duct 2" away from the ceiling. The co2 and fan don't run at the same time. I was looking for a way to cut down on radiant heat to shorten the cycle of my fan. In the future I plan on buying a water cooled burner but as it stands now I use 10-12 cans a grow @ $21 a refill.

Will there be condensation even if the outside RH is in the low 20's?
 
alcohol

alcohol

Active Member
I dont like messing with all of the ducting. It makes it hard to move lights around. It makes it difficult to use light movers easily. You need a fan for each run and cannot run more than 2 ducts in a row, ideally. If the ducting isn't metal, it melts, then you have to buy new ducting. LOL.

I just bought a mini split and was done with it. I enjoyed the results. I know a few people who use ducting well. I think you need it for tents.
 
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