How maximum outdoor air flow rate is calculated in Controller:OutdoorAir?
I am trying to implement PAU+FCU with chilled water loop.
Since maximum flow rate specified in Fan:VariableVolume is bigger than minimum flow rate autosized by Controller:OutdoorAir, I expected that maximum flow rate specified in Fan:VariableVolume will be used for maximum flow rate in Controller:OutdoorAir. However, checking the result, maximum flow rate is same as minimum flow rate as shown below.
Then I start to wonder how maximum flow rate for economizer is calculated.
Can anyone tell me how maximum outdoor air flow rate is calculated in Controller:OutdoorAir?
Followings are some of the objects I mentioned.
Controller:OutdoorAir,
A_LZ_Office_sys OA Controller, !- Name
A_LZ_Office_sys Relief Air Outlet, !- Relief Air Outlet Node Name
A_LZ_Office_sys Air Loop Inlet, !- Return Air Node Name
A_LZ_Office_sys Mixed Air Outlet, !- Mixed Air Node Name
A_LZ_Office_sys Outdoor Air Inlet, !- Actuator Node Name
autosize, !- Minimum Outdoor Air Flow Rate {m3/s}
autosize, !- Maximum Outdoor Air Flow Rate {m3/s}
DifferentialEnthalpy, !- Economizer Control Type
ModulateFlow, !- Economizer Control Action Type
, !- Economizer Maximum Limit Dry-Bulb Temperature {C}
, !- Economizer Maximum Limit Enthalpy {J/kg}
, !- Economizer Maximum Limit Dewpoint Temperature {C}
, !- Electronic Enthalpy Limit Curve Name
, !- Economizer Minimum Limit Dry-Bulb Temperature {C}
NoLockout, !- Lockout Type
ProportionalMinimum; !- Minimum Limit Type
Fan:VariableVolume,
A_LZ_Office_sys Supply Fan, !- Name
Office HVAC On (BEAM), !- Availability Schedule Name
0.8, !- Fan Total Efficiency
1600, !- Pressure Rise {Pa}
145.2, !- Maximum Flow Rate {m3/s}
Fraction, !- Fan Power Minimum Flow Rate Input Method
0.0, !- Fan Power Minimum Flow Fraction
, !- Fan Power Minimum Air Flow Rate {m3/s}
0.9, !- Motor Efficiency
1, !- Motor In Airstream Fraction
0.0015302446, !- Fan Power Coefficient 1
0.0052080574, !- Fan Power Coefficient 2
1.1086242, !- Fan Power Coefficient 3
-0.11635563, !- Fan Power Coefficient 4
0, !- Fan Power Coefficient 5
A_LZ_Office_sys Heating Coil Outlet, !- Air Inlet Node Name
A_LZ_Office_sys Supply Fan Outlet; !- Air Outlet Node Name
Are you working from the same file you posted here? In those posted objects you have used "NoEconomizer" in the setting for the
Economizer Control Typefield in theController:OutdoorAir. Did you change that setting for the run results shown here?The one you mentioned is different model. I added the
Controller:OutdoorAirobject to the post.Where is your
Controller:MechanicalVentilation? DId you read the I/O, the intro section is pretty explanatory.I didn't model
Controller:MechanicalVentilationsince I thought that it is not required to model air side economizer. I read the I/O. They explain how the outdoor air volume is decided according to outdoor and indoor condition. However, cannot find howMaximum Outdoor Air Flow Rateis calculated when we set to autosizedWhat is the design flow rate of the system when you look at the output reports and/or in the
Sizing:Systemobject? I suspect that max flow rate of the supply fan is not enforced in any way to be the same as the system max flow rate.The fan flow rate in theFan:VariableVolumeobject would just be used to determine part load ratio of the fan needed calculate the power use in simulation.