Typical return air conditions

[etwizz]

Hi,
I'm looking into a enthalpy wheel for treating 100% outdoor air (comfort cooling), but I'm not sure what conditions I should be using for the return air and the customer has not been able to answer this question. Does anyone know of any reference for typical return air condition or any way of approximating the heat/moisture gain or loss.

Thanks,
etwizz

 

[imok2]

try this:

http://www.drirotors.com/pdf/articles/iaq/tfa_dp_new.pdf

 

[quark]

Ideally, it should be your room condition. I would add 1 to 2⁰C as return duct gain. Humidity remains same.

 

[lilliput1]

Check return air (exhausted at the heat recovery wheel) CFM. It may not be equal to your OA. RA CFM = SA CFM - Pressurization CFM - Exhaust air not returned to the heat recovery wheel.

 

[HVAC68]

Depends on how you are taking back the return air. If it's through a ceiling void and the floor above is either non-AC or exposed to sun and you have lights which emit heat above the ceiling, then the return air would pick up this heat (the heat gain on account of lights and the wall/ceiling/roof gain which is the above the false ceiling) resulting in a much higher return air temperature.



HVAC68

 

[ChasBean1]

You're talking about a summer condition and the acceptable indoor condition (high end) varies in different regions of the world. I would use a return of 75°F, maybe 55% RH.