Grow Room Dehumidifier

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You’re adding 25 gallons of water a day (200 pints per day) to the plants, so you buy a dehumidifier rated at 200 pints per day to control humidity. Everything is fine during the day (or when lights are on), but night climate conditions spin out of control.

A dehumidifier rated at 200 pints a day in warm, moderately humid conditions (80F degrees @ 60% relative humidity) only removes a few pints an hour in cool, dry night environments. If you need to maintain 75F degrees @ 50% relative humidity, you must know the rating of your dehumidifier at that condition.

The proper size dehumidifier for your project depends upon the lowest temperature and desired humidity in your facility. Undersized dehumidifiers result in higher humidity levels just as an undersized air conditioner would provide a high room temperature. Discuss your project with an experienced equipment supplier or product engineer.

 

[queequeg152]

there is a shitload of ways to contol humidity beyond a dedicated dehuy.

you are ignoring the fact that a properly sized and installed ac unit can remove the vast bulk of the humidity itself.

during off hours when the heat load is very small you can get into issues, that require over cooling, and reheating.
but less so if you have a variable speed air handler or VRF system or multistage system that can vary capacity and or air flow across the evaporator coil.

its also worth considering adding an economizer system to your equipment in these situations... as outside humidity may or may not be far below indoor conditions.

when the economizer board detects this condition a damper is opened, and outside air is brought inside, reheated as necessary, and hot moist air is exhausted simultaneously... through an ERV if necessary.

the issue with oversized dehumidifiers is that wet coils post shut down are allowed to evaporate back into the conditioned air reducing the efficiency.

you want to run a dehumidifier on as long a duty cycle as is possible. to do that id suggest that you data log the relative humidity and temp overnight, then calculate the peak rate of enthalapy at 80 degrees or what ever your ac cut out is. 80+ would be ideal as dehuys operate more efficiencly at higher air enthalapys.

 

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You are quite educated on the topic queequeg. I really like the ERV concept for Colorado and Washington state at night or cooler seasons. I've proposed it before, but it takes a special person to understand that you're not blowin' smoke (ha, ha) up their ass.

 

[queequeg152]

ERV units are PAINFULLY expensive... i wish this was not the case because i love them , but unfortunately they are often far to expensive and small capacity for some use cases.

 

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You've seen that corrugated plastic sign board. It has square channels through the board. Why couldn't you alternate and stack that to make a cheap ERV with a couple of fans?

 

[queequeg152]

you can actually. there are a few folks diying stuff exactly like that inside the agressive passive house community.

problem is that stuff is not terribly resiliant, probably lasting only single digit years.
cleaning it would be problematic but not insurmountable.

imo what you want is stamped sheets of very thin stainless stee or aluminuml spot welded together like a plate heat exchanger. most of the very large ERV/HRV are of this type from what i could tell.

actually most of the very large ERV's are of the wheel design now that i think about it.

 

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checked out price of 10mm corrugated sheets, not cheap. PVC has low "k". Just thinking out loud through the blog. not very cost efficient.

 

[queequeg152]

greenhouse polycarbonate is not cheap... but probably cheap enough, idk what you are looking at, but i recall the thin greenhouse polycarbonate being less that 2 bucks a square foot.

200 bucks for a 100 sq.ft. heat exchanger? IDK. im not particularly interested in that hassle, but im shure it can be done.

from there you just need an enclosure... pretty much any sheet metal shop can built one, and some cowling made from... solvent welded ABS sheets and neoprene perhaps.