Dealing With RH in Small Space

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guitarguy10

Well-Known Member
To keep the temps in my small 2'x4' footprint under control I have to run so much exhaust that i can't keep the RH above 30% even with a humidifer in there, anyone know why? I have 600W HPS in there and AC infinity 6" exhausting at like half speed.
 
Your exchanging all the air in the tent with fresh air quickly in a small area. The humidifier is not really doing much in there.

Only way would be to raise the rh of your source of fresh air
 
Dont know much about HPS. I assume its in a hood? Can you exhaust the heat from the hood/lamp fixture separetly from the tent exhaust?
 
Is a 2'x4' footprint a 2'x4' tent? If so, dissipating 600w of heat in a volume that small will be problematic.
3-400w of LED would generate better light and 1/2 the overall heat, and much less radiant heat.
An often overlooked benefit of LEDs is that they allow you to run higher air temps.
 
guitarguy10 said:
@Soul Dwella yes it's in a hood and has it's own dedicated 250CFM exhaust fan.

@Billy the Mountain It's 2'x4'x6' and I have it at 75% brightness

@Failmore Can you suggest a room sized humidifier? I have a small one now meant for a small space a cool mist something but it's small and I bought it just for the tent
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Sorry dude. I'm also a 2x4 600hps guy. I just let the rh be what ever it is. Keep that light 24" or more. 600 is a lot in a 2x4 and I have a lot of issues from to much light. Specially when the rh is low.
 
Lower the temps in the room/tent to 75F-73F or so.. The hotter the air, the less RH it will hold, cooler air retains RH better..
With a 1K HPS, I would go thru 3-4 gallons of water a day to maintain 55% RH @ 78F (AC set to 78F). With AC set to 75F, using 1.5 gallons a day to maintain 50%RH. Leaf temps 76F-79F.
 
iffey said:
Lower the temps in the room/tent to 75F-73F or so.. The hotter the air, the less RH it will hold, cooler air retains RH better..
With a 1K HPS, I would go thru 3-4 gallons of water a day to maintain 55% RH @ 78F (AC set to 78F). With AC set to 75F, using 1.5 gallons a day to maintain 50%RH. Leaf temps 76F-79F.
Click to expand...

Isnt that backwards? Cold air holds less moisture. Condensation happens when warm air hits a cold surface because as the air cools, it cant hold as much moisture. Although It is true that as you decrease the temp of air, the "relative" humidity will go up. The amount of water vaper in it stays the same, but relative to the amount of moisture the cooler air can hold, the rh number increases as temp decreases, unless of course you decrease the temp to the point of condensation and moisture comes out.

Ive been dealing with this same issue and ive come to the conclusion that theres 2 options, 1) dont grow in winter when i have to suck in cold air that has almost no moisture, or 2) switch to sealed room with co2. I thought winter would be great because you never need ac, but it doesnt pay off. I have to heat at night even with lights on which uses way more power than ac, and i have to pump 5 gallons of water per day into the air just to hold 50%. Im thinking late summer/fall/early winter is better strategy. Seedlings at end of summer since they dont need high wattage heat generating lights, fair amount of moisture in air. Moving into cooler temps in fall as veg plants mature and start making their own humidity. Flower in early winter when lights get turned up and need more cooling. Air being brought in is dry but the plants are drinking a ton and putting out lots of moisture, also the point when we need lower humidity to avoid bud rot anyway.

Still i think id rather go sealed with co2 and led. Don't have to rely on outside conditions.
 
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