Evap temp based on Return air temp
Evap temp based on Return air temp
(OP)
We typically size our loads based on 75Deg F 50%RH return air. We have a project requiring 20,000 BTUH sensible cooling for 86 DegF 50%RH air. Most AC system design is based on approx. 45 DegF evaporating temp. How does this now equate with the 86 deg return air?
My understanding is the evap temp will be in the area of 55 degF. However, this is the outer operating limit of our compressor performance.
Can this load be "translated" to a different coil/compressor selection to reduce the evap temperature and run the compressor in a more common operating point? I have always thought the evap temp is a function of the return air temp?
Do I simply run the coil data software at 86 entering temp and 45 deg evaporating and select a compressor to match the cooling load at this evaporating temperature?
Regards,
NJG
My understanding is the evap temp will be in the area of 55 degF. However, this is the outer operating limit of our compressor performance.
Can this load be "translated" to a different coil/compressor selection to reduce the evap temperature and run the compressor in a more common operating point? I have always thought the evap temp is a function of the return air temp?
Do I simply run the coil data software at 86 entering temp and 45 deg evaporating and select a compressor to match the cooling load at this evaporating temperature?
Regards,
NJG





RE: Evap temp based on Return air temp
No, for the simple reason that you will never be able to cooldown the air temperature if it depends upon the return air temperature, in that case.
Why can't you go for chilled water application?
RE: Evap temp based on Return air temp
I may have been somewhat unclear with my question. When I say evap temperature, I am speaking of the saturated suction temp. Does this not "float" with the change in return air temperature?
RE: Evap temp based on Return air temp
The SST is dependent on the heat load on the coil, so as return temp across the coil increases then so does the SST. In other words the air off the coil may be say 60*F instead of 55*F
RE: Evap temp based on Return air temp
I'm not a real engineer, but I play one on T.V.
A.J. Gest, York Int./JCI