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# How to control rrelative humidity to 30%

## How to control rrelative humidity to 30%

(OP)
My process requires controlling relative humidity to <35%. I am currently in a very large open area and am considering building a 8 x 10 x 8' room with a flap door.

Humidity is currnetly at 94%, temperature is 64°.
Will a dehumidifier get me to <35%? (need to maintain temp between 65 and 80°).
What size unit do I need?
Are there any stumbling blocks I should be aware of?

### RE: How to control rrelative humidity to 30%

I don't know what is causing the high humidity and if the 64 dF has to be maintained.
Raising ambient temp would reduce RH. Installation of an AC. also would reduce RH and lower temp.  Probably the proposed construction with a heater or AC may be the answer.

### RE: How to control rrelative humidity to 30%

(OP)
Thanks for the help.
OK here's where I'm at now;
RH is holding at 30% but the temp in the room is at 27°C and it's feeling a bit stuffy in there.

Can I add a small room AC unit to bring in fresh air while keeping the dehumidifier running?

### RE: How to control rrelative humidity to 30%

You should try to keep referring to one set of temperature units Obviously originally oF-> So your limits were 18.3333333 - 26.6666667 oC
So there is flexibility in the temperature limits?

### RE: How to control rrelative humidity to 30%

(OP)
OK, we'll go back to °C.
The product I'm working with requires us to control the temp limits to 18 to 26°C, but it would be a better environment for our operators if we could maintain a temp closer to 21°C.

### RE: How to control rrelative humidity to 30%

A dehumidifier is essentially a heat pump, therefore theoretically you would see an increase in temperature which explains the stuffiness.  Without knowing the details about the parameters affecting temperature and RH, from the seat of my pants, I would say an AC and a humidifier in the proposed room.

### RE: How to control rrelative humidity to 30%

You want to tightly control the air exchange due to the amount of moisture you are seeing in the air outside of your control area. I would set up a wall mount AC unit, rejecting heat outside of the room. That would give you the best of both worlds, it would also act as a dehumidifier through the condenser coil. So it probably won't have to run as much. Probably could take your 80 F current temp down to 70 F as well as keep your dehumidifier from running all the time. Just make sure your condensate drains outside of your control area. Since your are only in an 80 sq ft area I would think a 15,000 BTU wall unit would be acceptable.

Ryan Marks
Mechanical Engineer
http://www.stryker-tech.com/

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