An (almost) closed loop garden in a tent

[YYCannabis]

Hey, y’all.

Been a while since I’ve been here at GWE. Last garden was such an abundance I haven’t needed to grow again until recently. My mantra with my garden setup has always been to add/upgrade *something* with the start of each new grow. This time around, I’ve decided that i would invest in temperature control.

After some searching around, i found what i believe is the best option for a tent or small grow room. The big green and black box sitting on the shelf is marketed as a portable Air/con for camping and tenting. This is not just an ordinary air conditioner, but is actually a mini-split heat pump system combined in one unit. The grill facing the camera is the air intake and exhaust for the tent. This circulates and cools the air within the garden without creating a push-pull air flow into and out of the space. There are two vent ducts that can be seen coming from the rear of the unit. These push/pull air outside of the tent and do not change the garden environment. The lower vent pulls-in air, from the room my tent is in, and then the upper vent is ducted outside as the exhaust temp is >45C. I’m not sure how it will impact the humidity in the tent and my VPD. I’ve been running a single disk ultrasonic water vapor unit trying to get the humidity up (bottom shelf grey pail) but it’s undersized and i regret not getting a unit with more emitters to help raise the RH faster when i need it.

** I’ll do a pros n cons in the next post**

As you can see in the pics, my garden is in flower, and is a bit chaotic in plant heights so far, so i had to adjust my lights to an extreme angle to get top-down and sideways light direction. (I really hope the plant on the right slows down, or the others grow up quickly LOL). The plant on the left was germinated about 10 days behind the others, so it’s behind in growth so far. All are autos, (left to right) White Widow, Cake Crasher, Donny Burger, and finally Bubba White (The tall girl). Sadly, the White Widow had a sickly moment after germination and now has a bent trunk.

[YYCannabis]

PROS N CONS

Let me start with the Pros:
- Very energy efficient just as heat pumps are designed to be. My lights are 600W with each strip emitting heat at ~39C and there is currently 18 strips of LEDs. It has been awesome at holding the temperature in the tent to within acceptable limits of 22C to 28C.
- Quiet. It’s surprisingly quiet.
- the size works for my garden size of 4’x8’ with only 4 plants (Canadian legal limit). I have the space inside my tent to hove the AC unit in there, but it can also be reconfigured to have the unit outside the tent, and use the vent ducts on the front side of the unit running in/out of the tent. Same benefit as my setup, just moving the vent ducts.
- dehumidifies the air as it cools it. *SEE ALSO: CONS*
- water condensation helps replenish the bucket for the fog emitter.

Cons:
- dehumidifies the air as it cools it. I don’t know yet how much it will try to dry the air as the plants get bigger. This is making it a challenge to get my VPD into a good range.
- it advertises that it shuts down when temp is reached, but mine hasn’t shut down fully even when the set temp is reached. It keeps running at a very low power level instead of just turning off.
- heavy as hell. Don’t think about putting this on a flimsy plastic table.
- the external air side exhaust vent gets very very hot. I had to cover it with insulation so it would stop radiating heat back into the space it is trying to cool.

Unknowns:
- We haven’t had much for warm temps here, so my grow room ambient temps have been between 5C at night and 15C during the day. Once the weather warms up and the ambient temp in the room gets over 25C, i don’t know how well the AC will do its job so stay tuned for that. If it struggles, then I’ll have to add an AC to the room to control the ambient temp and ease the stress on the tent space AC.
- Humidity…will i ever get my RH and temp to align? Currently it’s at 22-24C and a RH of 53%. I want my RH to be between 60-75% and haven’t been able to get there yet.

[YYCannabis]

Trying to get to a closed loop system, i am stuck at a cross roads for dealing with odor and excessive heat/humidity crisis situations.

I have my carbon filter scrubber setup venting outside. Since there isn’t much stank from the girls yet, I haven’t had to start air scrubbing. Usually, my air scrubber is triggered to come on at either excessive tent over-temperature control or too high RH control.

If i close loop the scrubber, then i lose the ability to deal with environment issues in the tent if that AC unit fails unless i buy another exhaust fan and charcoal scrubber. Stay tuned…i might have to go shopping LOL.

[golfnrl]

Welcome back. That grow space is awesome. I'd love to have the space around my place for something like that. thanks for sharing the upgrade info. I'm considering one of those split units for my outdoor kitchen. Looks like to me the portable AC allows you to create a lung room for growing wherever its needed or wanted and that is a very cool thing. My grow tent is in a spare BR with its own HVAC zone. I fell into that one and did not know how good that really is. Over time I've figured out how to manage the temps and RH for my situation but it has been a journey. I am now using AC Infinity humidifiers for each of my grow tents, a 4x4 and a 2x4. I was skeptical about their ability to maintain any kind of consistency but after using them, I'm a believer. I have them attached to the ACI controller. The RH stays at whatever level I have set. That works well for the time of year in my location because I need to raise the RH. I'll need to lower it as summer approaches. The lung room AC handles that and lowers the RH in the tent. I've tried in-tent de-humidifiers and I haven't found one that worked. What are you using to raise the RH?

What are those blue hangers for? Drying? Maybe plant support?

[YYCannabis]

Hey golfnrl
Those blue hangers are for drying. I figure that the best place to keep them so they don’t tangle and break, is to keep them in the tent.
For raising the RH i have just one little ultrasonic device from Amazon.But it’s too small, so i need to get a larger one soon.

[Bluey]

I'm running two heat pump air-conditioning units in my flower room. It's 11x7foot, pretty well sealed, and I do 5 full size plants max that produced over a pound each of premium first rate bud and almost another pound each of lower grade bud for extracts. I run 2050W of full spectrum LED lighting with the canopy foot print about 10 x 5.Im not running a carbon filter to keep negative pressure inside the room and you can smell my dank from the public road. This is an issue I need to rectify.

I have high humidity where I live. I also run a 50ltrs/day dehumidifier that runs flat out 24/7 from mid flower onwards.

One AC stays on 24/7 once lights get to 100%, that's a 1.5kw cool wall unit that vents about 5% fresh air. I can drop that back to zero.

The other unit I operate on its own thermostat and its a 3.1kw cool unit that functions the same as yours. I have it set up to only exhaust the hot air which reduces its effectiveness as a dehumidifier and also draws in a bit more fresh air into the flower room from outside. It sits in the flower room.

So it's a bit of a compromise. As soon as you introduce AC you're lowering RH in the room. Setup the way you have it will lower it more but it substantially reduces air changeover....so I guess you just have to trial it and see how it works for you best.