Super High RH% During Flowering

I installed a dual hose a/c unit to help with the temps, however, when the lights are off and the a/c isn't compressing, which I am only assuming controls the dehumidifying, the RH% literally climbs up by the second into the 80-85%. After a couple of minutes the a/c unit will kick on to cool down the area, and the RH will drop back down to ~60%, and instantly begin climbing once the a/c shuts off a minute later.

No issues during lights on.. guessing the light takes away some of the humidity?

What can I do in this kind of situation? The a/c unit has a drain line for the built up water, however, it's supposed to be a self evaporating system that vents out with the hot air. I was considering the possibility of rigging up the drain line for the a/c unit, but that would be a lot of work for a solution that might not be effective. Thoughts?

You could consider a dehumidifier but I'm really not sure what the mold risk is if you yo yo, maybe not an issue?

Bugeye said:

You could consider a dehumidifier but I'm really not sure what the mold risk is if you yo yo, maybe not an issue?

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It's a bit unfortunate about my situation, because my a/c unit has the built-in dehumidifier. I wish there was a programming interface where I could have a/c mode enabled during lights on, and dehumidifying mode after lights off. I don't think I would have enough room in my flowering area to add another machine like a dehumidifier to be honest with you.

JohnCee said:

It's a bit unfortunate about my situation, because my a/c unit has the built-in dehumidifier. I wish there was a programming interface where I could have a/c mode enabled during lights on, and dehumidifying mode after lights off. I don't think I would have enough room in my flowering area to add another machine like a dehumidifier to be honest with you.

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I wish you luck. I've only had mold spore germination from long periods of high humidity.

I had high RH in flower for a while - I microscoped some fresh picked buds and could already see wispy white strands throughout my trichromes.
Might want to monitor your plants with a microscope

GreenLogician said:

I had high RH in flower for a while - I microscoped some fresh picked buds and could already see wispy white strands throughout my trichromes.
Might want to monitor your plants with a microscope

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Good call, can also spray your plants down with diluted H2o2 to kill mold spores proactively before they go off.

Self evaporating AC's are a prime example of marketing-driven engineering. I would try and use the drain line if at all possible if only for prevention of mold growth in the AC itself, which will then blow spores all over.

The lights don't take away humidity, they merely raise the air temperature which lowers the relative humidity because the amount of water vapor that air can hold is relative to it's temperature (and barometric pressure, but we're assuming this is a constant in your grow room). Warmer air can hold more water vapor than cold air, so the same amount of water vapor in the air registers a lower RH at a warmer temperature.

Is there a specific danger zone for RH to lead to mold?

ladywolf said:

Is there a specific danger zone for RH to lead to mold?

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XipXipXoom said:

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Oh my gosh, a graph, I love it! Thank you!!