Preventing condensation on air-cooled hoods

[Apophis]

I have two 1k PL reflectors with hoods, sealed, with one 600cfm can fan, this config works very well for controlling temps. I ran reflectors without hoods for years exhausting the air throughout the grow room. I recently added a co2 burner, hence the sealed hoods. Temps are starting to drop causing some serious condensation on the inlet of the first hood, which I'm sure is only going to get worse as temps continue to fall outside. I have a de-humidifier that runs 24hrs inside the room, and RH runs about 45-55%. It's obvious the outside air has to be dried or warmed to within 15 degrees of ambient air inside grow room. Don't feel like experimenting, so, to those with experience with sealed hoods, what is the best way to counteract this?

 

[ogluver]

maybe grab the air from an attic instead of outside

 

[GroHi]

I would venture to guess the problem is neither the hood nor the outside air temps, but rather it is the RH in your room and/or your closed air environment. The burner is likely putting out more moisture than the dehumidifier can handle which is why you are still over 55%, which is getting high. At this point, I'm seriously getting concerned about mold issues... and since you actually see condensation within parts of your room, even if it is just the hood...?

The only way to ultimately address the issue is to rework your ventilation model & begin to exchange some of the air. Have personally gone the route of adding 3 dehumidifiers to a room to attain the CAE model... and it didn't work. Peace.

 

[mrdizzle]

its from cold air hitting a hot light, you need to pull ambient air, it has absolutly nothing to do with the RH of your room

 

[jadins_journey]

its from cold air hitting a hot light, you need to pull ambient air, it has absolutly nothing to do with the RH of your room

your absolutely correct, has nothing what so ever to do with RH in your room. Either do what mrdizzle said or use some form of heat exchanger to warm your incoming air. I just did a quick google search for "heat exchangers" and came up with some simple ideas.

Condensation on a 1K bulb is not a good thing,

jj

 

[GroHi]

This isn't correct. If you have more water in the air, the temps differentials causes it to condense from gaseous form to water droplets. You are seeing water condensing which is coming from the air. How could the total amount of water in the air not effect this? The temps & RH & condensation are intimately connected. Peace to all.

 

[Apophis]

I don't think pulling air from the attic will work, the 600cfm fan would evacuate the entire volume of air in the attic in less than 10 min and then I would be back to pulling in 40 degree air. I don't like the idea of heating the air that I need to cool the lights, kinda defeats the purpose heh? I mean, it would take a 1k watt heater to keep up plus the 130 watt can fan . . . thats too much extra juice to cool 2 lights.

It takes the burner 1min 45sec to bring the room to 1600ppm on the high setting, and then maintains a min of 1500ppm by running less than 30sec every 15 to 20 min. I don't think the burner is running more than 20 or 25 min total during the 12hrs that the lights are on. I'm pretty sure the dehumidifier can handle this. And I agree, rh does play a role as far as condensation rates . . . high humidity - more condensation, low humidity - less condensation, you're always gonna see some when ramming 40 degree air into 100+ degree air.

I think the cheapest way may be to create a closed loop in my 6" ducting to use the heated air from the lights, just need to figure out a way to regulate the cold outside air into the loop keeping it around 70 degrees or so. It seems that this might be difficult when temps change 10 or 20 degrees. Something like a louvered vent operated by a solenoid that would open and close automatically by a temperature sensor . . .anyone know of such? Looks like I may be experimenting again.

I guess the only choice I have for now is to pull the safety glasses out of the hoods, block off the exhaust inlet and let the mini split deal with the heat. Damn thing pulls over 1400watts and hardly ran during warmer days when I could make use of the sealed hoods and fan. I used to look forward to fall and winter because of the decreased usage in electricity, nothing lasts forever I guess.

Thanks guys.

 

[GroHi]

That's an interesting idea... closing the loop yet keeping a large portion of it in the "cooler" area as that would still exchange the heat. Depending upon how this works, condensation may be limited to a specific area or even eliminated. Probably would have to set it up & see how it performs though. A catch/dip at the dew point area might work & just poke a hole in the bottom to drain...? Hard to picture exact set-up as what's in my head likely doesn't look the same as you have...?

Perhaps a simple cloth (or something to absorb the moisture) at the point of condensation, but that is a stretch & would require change outs. Peace brother... sounds to be a dial'n in issue for you. Green vibes!