Re: [EnergyPlus_Support] Air flow rate error

Check the supply air flow inputs in the AirLoopHVAC:UnitaryHeatPump:AirToAir object

From: EnergyPlus_Support@xxxxxxxxxxxxxxx [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of Miroslav Bratanov
Sent: Tuesday, February 26, 2013 11:11 AM
To: EnergyPlus Support
Subject: [EnergyPlus_Support] Air flow rate error

Hello all,

I can't understand what exactly is causing this error:

   ** Severe ** AirLoopHVAC:UnitaryHeatPump:AirToAir = PSZ HP F014 HEAT PUMP
   **   ~~~   ** ... air flow rate = 2.9490954E-002 in fan object PSZ HP F014 SUPPLY FAN is less than the maximum HVAC system air flow rate in cooling mode.
   **   ~~~   ** The Supply Air Flow Rate During Cooling Operation is reset to the fan flow rate and the simulation continues.
   ** Severe ** AirLoopHVAC:UnitaryHeatPump:AirToAir = PSZ HP F014 HEAT PUMP
   **   ~~~   ** ... air flow rate = 2.9490954E-002 in fan object PSZ HP F014 SUPPLY FAN is less than the maximum HVAC system air flow rate in heating mode.
   **   ~~~   ** The Supply Air Flow Rate During Heating Operation is reset to the fan flow rate and the simulation continues.

The total cooling capacity is 488.18 W, so the maximum air flow rate should be 488.18*0.00006041 = 0.029490954 m3/s

Any suggestions?

Thank you!
Miroslav

==============================

This is how the objects are defined in the .idf file:

Branch,
    PSZ HP F014 Main Branch, !- Name
    0.02940954,              !- Maximum Flow Rate {m3/s}
    ,                        !- Pressure Drop Curve Name
    AirLoopHVAC:OutdoorAirSystem, !- Component 1 Object Type
    PSZ HP F014 OA System,   !- Component 1 Name
    PSZ HP F014 Air Loop Inlet, !- Component 1 Inlet Node Name
    PSZ HP F014 Mixed Air Outlet, !- Component 1 Outlet Node Name
    Passive,                 !- Component 1 Branch Control Type
    AirLoopHVAC:UnitaryHeatPump:AirToAir, !- Component 2 Object Type
    PSZ HP F014 Heat Pump,   !- Component 2 Name
    PSZ HP F014 Mixed Air Outlet, !- Component 2 Inlet Node Name
    PSZ HP F014 Air Loop Outlet, !- Component 2 Outlet Node Name
    Active;                  !- Component 2 Branch Control Type

AirLoopHVAC,
    PSZ HP F014,             !- Name
    ,                        !- Controller List Name
    PSZ HP F014 Availability Managers, !- Availability Manager List Name
    0.02940954,              !- Design Supply Air Flow Rate {m3/s}
    PSZ HP F014 Branches,    !- Branch List Name
    ,                        !- Connector List Name
    PSZ HP F014 Air Loop Inlet, !- Supply Side Inlet Node Name
    PSZ HP F014 Return Air Outlet, !- Demand Side Outlet Node Name
    PSZ HP F014 Supply Path Inlet, !- Demand Side Inlet Node Names
    PSZ HP F014 Air Loop Outlet; !- Supply Side Outlet Node Names

Fan:OnOff,
    PSZ HP F014 Supply Fan, !- Name
    OFF,                     !- Availability Schedule Name
    0.4,                     !- Fan Efficiency
    727,                     !- Pressure Rise {Pa}
    0.029490954,             !- Maximum Flow Rate {m3/s}
    0.825,                   !- Motor Efficiency
    1,                       !- Motor In Airstream Fraction
    PSZ HP F014 Heating Coil Outlet, !- Air Inlet Node Name
    PSZ HP F014 Supply Fan Outlet; !- Air Outlet Node Name

Coil:Cooling:DX:SingleSpeed,
    PSZ HP F014 Cooling Coil,!- Name
    ALWAYS_ON,               !- Availability Schedule Name
    488.18,                  !- Rated Total Cooling Capacity {W}
    0.798655,                !- Rated Sensible Heat Ratio
    3.2,                     !- Rated COP {W/W}
    0.029490954,             !- Rated Air Flow Rate {m3/s}
    ,                        !- Rated Evaporator Fan Power Per Volume Flow Rate {W/(m3/s)}
    PSZ HP F014 Mixed Air Outlet, !- Air Inlet Node Name
    PSZ HP F014 Cooling Coil Outlet, !- Air Outlet Node Name
    PSZ HP F014 Cool Coil Cap-FT, !- Total Cooling Capacity Function of Temperature Curve Name
    PSZ HP F014 Cool Coil Cap-FF, !- Total Cooling Capacity Function of Flow Fraction Curve Name
    PSZ HP F014 Cool Coil EIR-FT, !- Energy Input Ratio Function of Temperature Curve Name
    PSZ HP F014 Cool Coil EIR-FF, !- Energy Input Ratio Function of Flow Fraction Curve Name
    PSZ HP F014 Cool Coil PLF, !- Part Load Fraction Correlation Curve Name
    0,                       !- Nominal Time for Condensate Removal to Begin {s}
    0,                       !- Ratio of Initial Moisture Evaporation Rate and Steady State Latent Capacity {dimensionless}
    0,                       !- Maximum Cycling Rate {cycles/hr}
    0,                       !- Latent Capacity Time Constant {s}
    PSZ HP F014 Cooling Coil Condenser Inlet, !- Condenser Air Inlet Node Name
    AirCooled,               !- Condenser Type
    0,                       !- Evaporative Condenser Effectiveness {dimensionless}
    ,                        !- Evaporative Condenser Air Flow Rate {m3/s}
    0,                       !- Evaporative Condenser Pump Rated Power Consumption {W}
    0,                       !- Crankcase Heater Capacity {W}
    10;                      !- Maximum Outdoor Dry-Bulb Temperature for Crankcase Heater Operation {C}

Coil:Heating:DX:SingleSpeed,
    PSZ HP F014 HP Heating Coil, !- Name
    ALWAYS_ON,               !- Availability Schedule Name
    488.18,                  !- Rated Total Heating Capacity {W}
    3.2,                     !- Rated COP {W/W}
    0.029490954,             !- Rated Air Flow Rate {m3/s}
    ,                        !- Rated Evaporator Fan Power Per Volume Flow Rate {W/(m3/s)}
    PSZ HP F014 Cooling Coil Outlet, !- Air Inlet Node Name
    PSZ HP F014 Heating Coil Outlet, !- Air Outlet Node Name
    PSZ HP F014 HP Heating Coil Cap-FT, !- Total Heating Capacity Function of Temperature Curve Name
    PSZ HP F014 HP Heating Coil Cap-FF, !- Total Heating Capacity Function of Flow Fraction Curve Name
    PSZ HP F014 HP Heating Coil EIR-FT, !- Energy Input Ratio Function of Temperature Curve Name
    PSZ HP F014 HP Heating Coil EIR-FF, !- Energy Input Ratio Function of Flow Fraction Curve Name
    PSZ HP F014 HP Heating Coil PLF, !- Part Load Fraction Correlation Curve Name
    PSZ HP F014 HP Heating Coil DefrEIR-FT, !- Defrost Energy Input Ratio Function of Temperature Curve Name
    -8,                      !- Minimum Outdoor Dry-Bulb Temperature for Compressor Operation {C}
    ,                        !- Outdoor Dry-Bulb Temperature to Turn On Compressor {C}
    5,                       !- Maximum Outdoor Dry-Bulb Temperature for Defrost Operation {C}
    0,                       !- Crankcase Heater Capacity {W}
    0,                       !- Maximum Outdoor Dry-Bulb Temperature for Crankcase Heater Operation {C}
    ReverseCycle,            !- Defrost Strategy
    Timed,                   !- Defrost Control
    0.058333,                !- Defrost Time Period Fraction
    0;                       !- Resistive Defrost Heater Capacity {W}

AirTerminal:SingleDuct:Uncontrolled,
    F014 Air Terminal,       !- Name
    ALWAYS_ON,               !- Availability Schedule Name
    F014 Zone Equip Inlet,   !- Zone Supply Air Node Name
    0.02940954;              !- Maximum Air Flow Rate {m3/s}