I have a small room in my basement. i need to keep it cool and dry. The area of the room is 8' x 6'. I setup a portable A/C unit the unit is set to 66 deg. The temperature comes down but the humidity goes up it is constantly 7 to 10 percent higher than the rest of the basement. i have a Peltier dehumidifier in the room it is drawing moisture from the room.

Can anyone give me ant ideas on how to lower the humidity.

Thank you

 

All peltier dehumidifiers are quite small and can remove a limited amount of moisture from the air. A traditional compressor style dehumidifier will have much more capacity and should be able to get the humidity down where you want.

A problem with an AC unit in the basement, especially further north, is that the unit not may run often enough to remove enough moisture from the air. A basement will naturally stay cool so there isn't a need for the AC to run very often.

When you say "portable" AC do you truly mean a portable AC or a window unit? If it is a portable AC where is the condensate draining or getting out of the basement?

 

The A/C unit is new and working. The dehumidifier is working, the room is only 8' x 6'. i need to keep the temp around 65 and the humidify 50 % or lower. The best i can get is 58-60. If i turn off the a/c temp goes up to 70.

 

You will have to add some heat back into the room so the A/C can run longer.

In a small room like that I've used a window A/C and a dehumidifier at the same time.
Your A/C is cooling the room down too fast not allowing the moisture to be removed.

Doesn't the A/C have a thermostat that you can set ?

I see your using a Peltier as a dehumidifier. Are you allowing the heat generated to dissipate within the room ? That may help.

 

Yes and Yes. Not a lot of heat coming off the dehumidifier. Shouldn't the a/s remove some of the humidity?

 

The A/C will remove some moisture but since the room cools off quickly... the compressor doesn't run long enough.

 

You probably wont create one room with lower humidity because its all the same air. "Relative" humidity changes with the temperature, thus the name relative. Take a known quantity of 70F air, warm half of it to 75F... cool the other half of it to 65F... same air.... will have different relative humidities. Colder will be higher rh as the molecules are more concentrated.

Quit focusing on the fact the humidity is higher in the cooler room (because it will always read higher) and try to bring all the humidity in the entire basement down. FYI, you will likely not make much of a dent in it with one little dehumidifier.

And unless the A.C. is venting outside, its not really removing any humidity. Even if it is, any air it vents is being replaced with humid air from the rest of the basement. That air may seem dryer but its not. Chill it to 66F and the RH of that air goes up. Thats how RH works.

 

I sorry if i sound confused. The a/c is vented outside (portable unit). There is a door on the room the a/c is exhausting air and i'm sure the air has to come from somewhere. But why is the humidity is higher on the a/c side of the door than the rest of the basement. I plan on storing Chocolate in this room for the summer and i need to keep the temp in the middle sixty's and the humidity as close to 50% as possible.

 

It's similar to why your car has dew on it in the morning. As the temperature drops, the air gets closer to the dewpoint temperature which means the humidity is higher. You are just pulling in humid air from other parts of the basement. 70F air that's 50% RH will have a higher humidity when it is cooled down a few degrees... that's why the humidity is higher on your readings.

To get the RH in that room to 50% the rest of the basement air that is warmer would probably have to be 40% RH. That's just the way it works.

 

Thank you for the info. I thing i understand now. I'v turned bigger on the dehumidifier in the main basement. i'll see what happens.

Thank you again
John.

 

vent the AC back into the room and not outside or probably start with half and half.

 

Part of the problem is the portable AC unit if it is a single hose model which is why I asked to confirm if it was in fact a portable unit and not a window AC. Single hose portable air conditioners blow air outside. That creates a vacuum in the room so air is sucked into the room through cracks and gaps. So, while the AC is cooling the air it is also drawing in a LOT of fresh, humid air.