How to disable Parallel PIU Fan during cooling
I believe most of you guys know the answer to my question since VAV with PFP Boxes is very popular HVAC system a.k.a. Baseline System 8 in ASHRAE90.1.
I want to run Parallel PIU (Powered Induction Unit) Fan only during heating. When no heating, I want to turn it off, which is the correct PIU fan operation (see my previous post), but I don't know how to do it.
I tested with a slightly modified ExampleFile: HVACTemplate-5ZoneVAVFanPowered.idf.
I changed the terminal unit of SPACE5-1 from HVACTemplate:Zone:VAV to HVACTemplate:VAV:FanPowered (All the terminal units became VAV:FanPowered). Flow Type of HVACTemplate:VAV:FanPowered was changed to Parallel. I also changed the cooling/heating setpoints slightly (Cooling: 26degC, Heating:20degC) to make a clear difference between cooling and heating. After running the modified idf file, I opend the expidf file and edited AvailabilityManager:NightCycle as follows.
AvailabilityManager:NightCycle,
VAV Sys 1 Availability, !- Name
HVACTemplate-Always 1, !- Applicability Schedule Name
FanAvailSched, !- Fan Schedule Name
CycleOnAnyZoneFansOnly, !- Control Type
0.2, !- Thermostat Tolerance {deltaC}
Thermostat; !- Cycling Run Time Control Type
I referred to the section of AirTerminal:SingleDuct:ParallelPIU:Reheat in I/O Reference. I thought AvailabilityManager:NightCycle overrides the PIU fan schedule.
The chart below is the simulation result on one winter day and one summer day. The weather file is Chicago.
There are 1 system supply fan and 5 PIU fans (5 zones). As you can see, PIU fans operate on 7th July, although the heating load is exactly 0W in all zones throught the day. I thought there was something wrong with my AvailabilityManager:NightCycle setting. I tried other Control Type, other Cycling Run Time Control Type and adding Zonelist, but all in vain. How can I disable the Parallel PIU Fans when there is no heating?
All the relevant files are here. The EnergyPlus version is V9-6-0.
