I have two problems.
Fan Electric PowerofFan:SystemModelis constant although the fan airflow is variable.Fan:SystemModelis ON when Availability Schedule is 0 during midnight.
This post is related to my previous question. I have modelled PAU+AHU with AirLoopHVAC:DedicatedOutdoorAirSystem. As you may know, only Fan:SystemModel is allowed for modelling AirLoopHVAC:DedicatedOutdoorAirSystem. Fan:VariableVolume is not allowed. I have modelled PAU with DCV by CO2 concentration, so the outdoor airflow rate is variable, but Fan Electric Power is constant. I don't know why. Besides, Availability Schedule makes the outdoor airflow rate 0 during midnight of weekdays, but the fan consumes electric power for 24 hours. Please find the charts below.
My Fan:SystemModel input is as follows. Is there anything wrong with it?
Fan:SystemModel,
PAU_Tower12_Office_1 Supply Fan, !- Name
LEED_V4_OFFICE_VENTILATION, !- Availability Schedule Name
PAU_Tower12_Office_1 Cooling Coil Outlet, !- Air Inlet Node Name
PAU_Tower12_Office_1 Supply Fan Outlet, !- Air Outlet Node Name
autosize, !- Design Maximum Air Flow Rate {m3/s}
Continuous, !- Speed Control Method
0.2, !- Electric Power Minimum Flow Rate Fraction
1200, !- Design Pressure Rise {Pa}
0.9, !- Motor Efficiency
1, !- Motor In Air Stream Fraction
autosize, !- Design Electric Power Consumption {W}
TotalEfficiencyAndPressure, !- Design Power Sizing Method
, !- Electric Power Per Unit Flow Rate {W/(m3/s)}
, !- Electric Power Per Unit Flow Rate Per Unit Pressure {W/((m3/s)-Pa)}
0.7, !- Fan Total Efficiency
ASHRAE90.1 TABLE G3.1.3.15 Fan Power Curve, !- Electric Power Function of Flow Fraction Curve Name
, !- Night Ventilation Mode Pressure Rise {Pa}
, !- Night Ventilation Mode Flow Fraction
, !- Motor Loss Zone Name
, !- Motor Loss Radiative Fraction
General; !- End-Use Subcategory
, !- Number of Speeds
, !- Speed 1 Flow Fraction
, !- Speed 1 Electric Power Fraction
Fan curve input is as follows. It is based on ASHRAE90.1 TABLE G3.1.3.15.
I think there should be no problem with it becuase AHUs that have been modelled with Fan:Variable and with the same coeciffients as this fan power curve have variable Fan Electric Power.
Curve:Cubic,
ASHRAE90.1 TABLE G3.1.3.15 Fan Power Curve, !- Name
0.0013, !- Coefficient1 Constant
0.147, !- Coefficient2 x
0.9506, !- Coefficient3 x**2
-0.0998, !- Coefficient4 x**3
0, !- Minimum Value of x
1; !- Maximum Value of x
AirLoopHVAC:DedicatedOutdoorAirSystem and Fan:SystemModel use the same Availability Schedule, so Fan:SystemModel should be OFF during midnight, but it isn't.
AirLoopHVAC:DedicatedOutdoorAirSystem,
PAU_Tower12_Office_1, !- Name
PAU_Tower12_Office_1 OA System, !- AirLoopHVAC:OutdoorAirSystem Name
LEED_V4_OFFICE_VENTILATION, !- Availability Schedule Name
PAU_Tower12_Office_1 Zone Mixer, !- AirLoopHVAC:Mixer Name
PAU_Tower12_Office_1 Zone Splitter, !- AirLoopHVAC:Splitter Name
4.5, !- Preheat Design Temperature {C}
0.004, !- Preheat Design Humidity Ratio {kgWater/kgDryAir}
17.5, !- Precool Design Temperature {C}
0.012, !- Precool Design Humidity Ratio {kgWater/kgDryAir}
5, !- Number of AirLoopHVAC
VAV_TOWER12_28F, !- AirLoopHVAC 1 Name
VAV_TOWER12_26-27F, !- AirLoopHVAC 2 Name
VAV_TOWER12_25F, !- AirLoopHVAC 3 Name
VAV_TOWER12_23-24F, !- AirLoopHVAC 4 Name
VAV_TOWER12_22F; !- AirLoopHVAC 5 Name
