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Temp and Rh control year round in northeast

Temp and Rh control year round in northeast

Temp and Rh control year round in northeast

(OP)
I have a 12 X 15 X 12 room that i am trying to control temp to +,- .05°c and +,-5% rh. I have the temp problem undercontrol but the problem i have is reducing the rh in the room and i feel the problem is i cannot get the chilling cold enought to remove enough of the water i am thinking of going with a split system instead of the chilled water system.The problem i have is when winter comes around the head pressure is going to be to high. Is there a system i could chill the compressor coil with water to remove the problem of trying to run in below 20°f.I now use electric heat with constant cooling and the temp controls well. I figure if i could get the coils to remove more of the Rh I could actually get control of the Rh. This is needed to contol the temp and Rh in a dimensional lab. Any suggestions or help would be greatly appericated,Joe

RE: Temp and Rh control year round in northeast

Joe, at what temperature and humidity is the room to be maintained? You gave the variation band but not the actual control values. This bit of info would help.

Thanks, -CB

RE: Temp and Rh control year round in northeast

(OP)
It is going to be 68°F and 25 - 30% Rh. Another problem is adding Rh in the winter without effecting the room temp. Uniformity in the room is important so i cannot just put a humidifier in the room. I have heard about steam sprays and other ideas, that are not supposed to add to the room temp.

RE: Temp and Rh control year round in northeast

That's a very dry indoor environment for 68°F. If you dehumdify by cooling, the magic number (neglecting internal humidity gain) is 31-35°F, a value to which you would have to cool the incoming air during spring, summer, and fall (all conditions above outside air temperature of 35°F), which I would guess, without looking up ASHRAE bin values represents more than 75% of any given year.

This is not reasonably achievable with conventional chilled water or DX systems. You would need to seek out alternative dehumdification systems - e.g., desiccant dehumidifiers. I don't think Grainger would stock anything for your application because a normal dehumidifier uses a typical refrigeration circuit, which might get a room dewpoint as low as maybe 45°F, not 31-35°F to suit your need.

Search for desiccant (one S, two C's - if the seller can't spell it, it's probably not worth buying from them) and see what you turn up. Regards, -CB

RE: Temp and Rh control year round in northeast

(OP)
thanks for your info and the tips. JD

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