Help reducing humidity with window AC

[fartbox86]

Okay, I have two 3x5 tents with two plants in each. Zone 7A/b. Outdoor climate pics attached. Outdoor humidity has been around 70% ish dropping to 60ish later in the week. The lung room is 145 sq ft in the basement. I just moved everything into this room so it's a little messy.

I just purchased a Medea u-shaped air conditioner 8k btu for the window which you can see in the picture.

I'm having trouble keeping the humidity in check. The air conditioner is set to 72 yet the humidity is 60 RH. The air conditioner doesn't seem to be pulling humidity out of the room. I heard this can happen with oversized AC units however Google Gemini suggested going with the 8000 BTU AC because of the extra humidity the plants are going to put out. And the heat from the grow lights.

The AC has a dry mode which works well at decreasing the humidity in the room however it makes things very cold and it won't shut off. It just constantly dehumidifies.

So I've constantly been switching back and forth from the cool mode to the dry mode. I have plants at all different stages in this room so I need to tailor it to the the one and latest flowering stage.

Is this normal behavior or am I doing something wrong? I do have a separate dehumidifier in this room but I was really hoping the AC unit would take care of everything.

Any suggestions?

 

[compostmike]

That’s pretty normal behavior for a window AC, especially in a basement. An AC only removes water while the coil is cold and it’s actually running long enough to condense moisture. If the room hits temp fast, it shuts down or idles, but the plants, wet media, and basement air keep adding moisture the whole time.

The 8k unit may not be “wrong,” it’s just doing sensible cooling more than latent moisture removal. Dry mode works because it forces longer coil time, but yeah, the tradeoff is the room gets cold. That’s why most grow rooms end up using the AC for heat control and a real dehu for moisture control. The dehu adds some heat back, then the AC deals with that heat. Annoying, but normal.

Big thing I’d check from your setup: are both tents exhausting back into that same lung room? If they are, you’re basically dumping all the transpiration water right back into the basement room and asking the AC to catch it. Also make sure that U-shaped window setup is sealed well. Humid outdoor air leaking around the unit will fight you all day.

I’d also keep an eye on electrical load and condensate around all that gear. Basement + AC + dehu + tents + cords is where sloppy setup can bite you faster than the humidity itself.

You’re not really doing anything crazy wrong. You’re just finding out that AC and dehumidification are related, but they aren’t the same job.