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[EnergyPlus_Support] PAU problems

Dear all,

When I model the Primary Air Unit,  from outside to inside, the
equipments include: Outside Air Mixer, Cooling coil -
Coil:Water:Cooling,  Heating coil - Coil:Water:SimpleHeating,
Fan:Simple:VariableVolume.  There should be no return air for this system.

There are some problems about this system,

1. Central cooling design supply temperature is 14℃, Central heating
design supply temperature is 16℃. When the schedule for heating coil
and cooling coil both are available, the cooling coil and heating coil
work together. Even when the served zones need cooling only, the
heating coil also work.  The outlet temperature of the cooling coil is
13.19℃, the inlet temperature of the heating coil is 15.19℃, and the
supply fan outlet temperature is 16℃.  I wonder whether the heating
coil can stop working for the hours need cooling only, especially in
winter.   In the winter, there need cooling for some hours, but need
heating for some other hours, not sure about the exact hours.

2. I define the outside air method as flow/person. The person is
variable at different hours. The PAU is expected to provide the
variable fresh air with the variable fan, but the PAU supply air flow
rate is constant, the PAU outside air inlet flow rate is not constant.
The PAU Outside air mixer outlet flow rate is equal to the PAU outside
air inlet flow rate for some working hours, but PAU Outside air mixer
outlet flow rate is greater than the PAU outside air inlet flow for
some hours, which may be caused by recirculation of return air, I
think. What make this difference? The PAU supply air flow can be
variable and always equal to the PAU outside air inlet flow rate?   

I appreciate your help.

Jia 




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