How to control relative humidity to <35% 1

[tdw123456]

I have no experience in this area.
My process requires controlling relative humidity to <35%. I am currently in a very large open area near an open loading dock and am considering building a 8 x 10 x 8' room with a flap door. It's raining, humidity is currnetly at 94%, temperature is 64°. Will a dehumidifier get me to <35%? (need to maintain temp between 65 and 80°F). What size unit do I need? Are there any stumbling blocks I should be aware of?

 

[berkshire]

If you want to get your RH that low, do not use a flap door.
Seal the room. A 20 pint an hour dehumidifyer should get you close, depending, on how many times an hour that door is opened.
Also look at dessicant dryers and temperature control for the room.
B.E.

 

[AnotherEllis]

At 64°F ambient your wet bulb needs to be down at ~48°F to reach 35% RH. Check with your dehumidifier manufacturer to see if they can reach this.

Also, if the room gets opened and closed any at all you may want to consider humidity control in conjunction with room pressurization so you exfiltrate air at controlled conditions rather than infiltrate air at uncontrolled conditions.

For a cleanroom or process area I would do something like that, using a Munters type unit to supply makeup air at a dry enough condition to maintain the space design condition.

Depending on the conditions that could get expensive.

http://www.ellisconsultingengineers.com

 

[tdw123456]

Thanks for all the help,
I'm going to allow the temp to rise to ~75°F and try to make this work with a velcro sealed flap door. I will install provisions for a solid door in case that doesn't work.

 

[marcoh]

Thats a low RH to maintain if it is an open area near a loading dock. Would need to be sealed as airtight as possible to limit infiltration. Do the calcs with a couple of ACH infiltration and see what you need?

Is it acceptable to have RH spiking for short periods as the doors are opened?

 

[tdw123456]

short spikes of RH are acceptable to our process.

 

[tdw123456]

Thanks for all 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?

 

[berkshire]

This comes back to what I said about temperature control for the room.
A small air conditioner will help, but if you get the room too cool, your relative humidity will go up.
B.E.