# Dehumidification help



## Jeffrey Jay (Sep 22, 2009)

Hello

I have a situation where I have an oversized Bard wall mount (5 ton) cooling a closet sized server room that should have a 2.5 ton (don't ask-I told them so).
Now we have a server rack you can put a hand print on it' so wet.
I have the IFM at low speed and have a dehumidistat engaging the resistance heat coil during cool (upon dehum demand) and it is insufficient. It is not practical to install a smaller unit (custom truck trailer). Perhaps a refrigerant that is better suited (higher temp at given suction pressure) that will work better (decrease effective cooling) with the larger needed coils? Different compressor? Charge adjustment? 

Anyone willing to reach out of the box?


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## jmmech (Jun 18, 2009)

*oversized unit*

I have run into this problem many times. you can install an APR valve made by Rawal Devices. It is a special capacity control that enhances dehumidification without overcooling. I have installed over 20 of these valves in industrial, commercial and residential rtu, splits with 100 % success. Here's their info:
Rawal Devices Inc.
Woburn, Mass. (781)-933-3304
www.rawal.com
They will assist you in sizing for your application.
Good luck
Joe, Owner
J&M Mechanical Services, LLC
Woodbury, Ct.


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## Jeffrey Jay (Sep 22, 2009)

Interesting! I will check this out. Thank you Joe! 
I will try to update this post for the good of all as I saw minimal refrigi-fog issues on my initial search. :thumbsup:


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## Jeffrey Jay (Sep 22, 2009)

Follow up as promised...I (so far) have not installed the Rawal valve but I am ordering one for my next build. 
I was able to install a humidistat that (when calling for dehumidification) pulls in the electric heat contactor during cool. This is not approved by the a/c manufacturer due to the amperage increases but this is a 480 unit and I took all precautions required. 
So far this is keeping me out of the dew point zone. :001_unsure:


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## nicktech (Jun 22, 2009)

have you tried constant fan, with the humidistat controlling the compressor?


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## Jeffrey Jay (Sep 22, 2009)

Actually, having the fan run too much was part of the problem as well, seems it would bring in all kinds of warm humid air between cycles. Then the unit would cycle on, blow tons (pun int) of cold air, hit dew point and instant soggy server blues. I moved it to auto to cut down on that, kind of funny really. So far no news is good news.

Thanks


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## ccc256 (Jul 31, 2010)

that valve is cool a pre fab hot gas bypass with liquid inj and capacity control valve


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