Most accurate dehumidifier?

VILEPLUME · Sep 22, 2020

Hi all, I need some help on an accurate dehumidifier for a 8x12 grow room.

I'm currently using a toshiba 70 pint dehumidifier but its accuracy isn't the best. I bought a humidity controller which worked great, but when the dehumidifier came back on, there was a "getting ready" period where the humidifier took time to start drying the air again and the humidity climbed worse than the built in dehumidifier sensor to begin with.

Temps are good and stay within 2 degrees within 24hrs but humidity can't stay stable.

So I'm looking for a dehumidifier that can keep the room stable at 45-50% humidity.

Any recommendations? I live in Canada, so I'd need to be able to buy it here. Thanks!

Renfro · Sep 22, 2020

VILEPLUME said:
when the dehumidifier came back on, there was a "getting ready" period where the humidifier took time to start drying the air again

Any refrigeration based dehumidifier will have this issue. The issue is when you short cycle the compressor before the pressure has dropped on the high side of the refrigerant loop the compressor motor can experience a hard start or rotor lock. This is bad. So to prevent this many devices are designed with a delay to prevent this from happening. Even if you defeated this delay you would just burn out the compressor motor.

So the key would be sizing the unit exactly so that it runs all the time and holds the RH% right where you want it but that is impossible due to the fact your plants will transpire more moisture as they get larger and ambient RH% levels could also be a variable to some extent.

Other methods like desiccant dehumidification could get around this dead band / delay issue since it is just a fan motor, no refrigeration.

Keesje · Sep 23, 2020

Off topic:
You may also ask yourself whether you need such a tight bandwidth.
Make it a bit wider and your problem is also partly solved.
Sorry, this is not an answer to your question, but only meant as an informative contribution.

VILEPLUME · Sep 23, 2020

Renfro said:
Any refrigeration based dehumidifier will have this issue. The issue is when you short cycle the compressor before the pressure has dropped on the high side of the refrigerant loop the compressor motor can experience a hard start or rotor lock. This is bad. So to prevent this many devices are designed with a delay to prevent this from happening. Even if you defeated this delay you would just burn out the compressor motor.

So the key would be sizing the unit exactly so that it runs all the time and holds the RH% right where you want it but that is impossible due to the fact your plants will transpire more moisture as they get larger and ambient RH% levels could also be a variable to some extent.

Other methods like desiccant dehumidification could get around this dead band / delay issue since it is just a fan motor, no refrigeration.

Thanks for your detailed answer I appreciate it.

That's a good idea, I'll hang some desiccant dehumidification bags.

If I can ask, what do you run for dehumidification? I'm thinking of investing in a commercial dehumidifier but would it be cheaper just to run 2 compressor dehumidifiers? So when one is on a delay, the other one might not be and would give a more accurate RH?

Most accurate dehumidifier?

VILEPLUME

Well-Known Member

Renfro

Well-Known Member

Keesje

Well-Known Member

VILEPLUME

Well-Known Member

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