Negative Tent Pressure

Raho · Jul 24, 2017

Well done OldPhart!
Move the AC and dehu outside the tent, making the room a big lung room.
Condition the air to the temp and RH differential needed to maintain ideal conditions inside the tent.
IE: running both scrubbers as exhaust with passive or active intakes, if the temp gets too hot or too wet at the rate of exchange, adjust the temp/RH outside the tent as needed to correct.
For instance, if you want inside the tent to be 80 degrees/65% RH, outside the tent might need to be 72 deg/50%. Those numbers are hypothetical, you would need to adjust till you got the results you needed.
Differential will be greater the longer it takes you to exchange the air in the tent.

Zeez · Jul 27, 2017

With the type of air conditioner being used, it makes sense to leave it in the tent because it does three things;

1, It dehumidifies as it exhausts.
2, It regulates temperature based on the ambient temperature in the tent.
3, It provides a constant flow exhaust fan, with the outside dehumidifier constantly supplying fresh dry air in.

Durring fall and winter modes I can go full lung by taking cool air from the out doors.

Here the plenum combining three tents (veg, bloom, drying) into one exhaust vent.

OldPhart · Jul 27, 2017

OK, that makes a lot more sense... you have a LOT more going on than a single tent in a single room, that is what I was envisioning. With as much as you have going on, you will just have to figure out what works. I think you are doing well to balance that much stuff in the same room. Looks to be a basement as well, I miss my basement; all the concrete really helps to stabilize the environment.

zeke99 · Jul 27, 2017

OldPhart said:
This has been my go to cooling method, but I only run a 600w in a 40"x40" box. I just take that flex duct, and point it at the air intake at the bottom of the box, then vent out the top. I find that the air coming out the top of the box, is about 1 degree below the room temp, but if you put a sensor at canopy level, it is almost exactly room temp due to the radiation from the light. I have ran this combo with 5000 btu with a 600w box, to a 12000 btu with a 1800w box and have had great results. But there is normally a little tuning to be done.

At least I think I may have given you some different ideas. I haven't looked, but I bet there are threads here about using a lung room, they are great for stability and odor control.

Interesting. Can I pick you brain on this? Is the door to the room that the tent is in shut at all times? If so, obviously you've had success so even though your exhausting from the tent back into the same room, you're still providing enough CO2. Do you crack a window inside the room for fresh air intake?

ambertrich · Aug 10, 2017

Just a bit of info from an old fart whose used a number of portable AC's for growing, replace the thin plastic duct hose that comes with the AC unit for exhausting the hot air it produces with insulated duct. You can feel the heat radiating from the plastic hose back into the room before it gets exhausted, adding heat back to your environment.
As others have stated, I would put the AC outside the tent-still use insulated ducting.

Zeez · Aug 11, 2017

You guys are absolutely right. I'm thinking that putting it outside add using the insulated ducting for both the cool air and the exhaust is the way to go. Its just a matter of finding the duct transition that fits over the cold air vent on the portable a/c.

On the dehumidifier I duct taped sponge foam around the flange end of the duct transition so it gave a good seal around the output. Probably use that same rig on the a/c.

Thanks for the good advice and taking the time to help me think this through.

ambertrich said:
Just a bit of info from an old fart whose used a number of portable AC's for growing, replace the thin plastic duct hose that comes with the AC unit for exhausting the hot air it produces with insulated duct. You can feel the heat radiating from the plastic hose back into the room before it gets exhausted, adding heat back to your environment.
As others have stated, I would put the AC outside the tent-still use insulated ducting.

OldPhart said:
Oh crap, I can't do simple math today. I started thinking about those numbers and it wasn't coming out right. So I broke out the calculator, and sure enough, I was off by a factor of 2 somewhere. The volume of the tent is somewhere around 300 CF, so with 2x315's w/filters, I would guess you are getting somewhere around 300 CFM. 60 seconds/exchange isn't bad, I usually like to overkill things though.

Maybe some people that have more experience will drop some information on us both, I hate giving random advice about what has worked for me, as it may not work in different situations, such as the portable AC.

View Image

This has been my go to cooling method, but I only run a 600w in a 40"x40" box. I just take that flex duct, and point it at the air intake at the bottom of the box, then vent out the top. I find that the air coming out the top of the box, is about 1 degree below the room temp, but if you put a sensor at canopy level, it is almost exactly room temp due to the radiation from the light. I have ran this combo with 5000 btu with a 600w box, to a 12000 btu with a 1800w box and have had great results. But there is normally a little tuning to be done.

At least I think I may have given you some different ideas. I haven't looked, but I bet there are threads here about using a lung room, they are great for stability and odor control.

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Negative Tent Pressure

Raho

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Zeez

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OldPhart

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zeke99

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ambertrich

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Zeez

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