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Low Speed Gross Rated Total Cooling Capacity

asked 2020-02-16 08:21:45 -0600

Eric gravatar image

updated 2020-02-17 17:26:48 -0600

ngkhanh gravatar image

Hello,

I autosize Low Speed Gross Rated Total Cooling Capacity and High Speed Gross Rated Total Cooling Capacity for two stage DX cooling coil. Low Speed Gross Rated Total Cooling Capacity is 1/3 of High Speed Gross Rated Total Cooling Capacity. Is there any way I can change this ratio such as 35% in EnergyPlus?

Thanks,

Eric

Coil:Cooling:DX:TwoSpeed,
BaseSys13 CoilClg,        !- Name
    Always On,                !- Availability Schedule Name
    autosize,                 !- High Speed Gross Rated Total Cooling Capacity
    autosize,                 !- High Speed Rated Sensible Heat Ratio
    3.9094111254,             !- High Speed Gross Rated Cooling COP
    autosize,                 !- High Speed Rated Air Flow Rate
    ,                         !- Unit Internal Static Air Pressure
    BaseSys13 OACtrl OA System Mixed Air Node,    !- Air Inlet Node Name
    BaseSys13 CoilClg Outlet Node,    !- Air Outlet Node Name
    CoilClgDXQRatio_fTwbToadbSI,    !- Total Cooling Capacity Function of Temperature Curve Name
    CoilClgDXDblQRatio_fCFMRatio,    !- Total Cooling Capacity Function of Flow Fraction Curve Name
    CoilClgDXEIRRatio_fTwbToadbSI,    !- Energy Input Ratio Function of Temperature Curve Name
    CoilClgDXDblEIRRatio_fCFMRatio,    !- Energy Input Ratio Function of Flow Fraction Curve Name
    CoilClgDXEIRRatio_fQFrac,    !- Part Load Fraction Correlation Curve Name
    autosize,                 !- Low Speed Gross Rated Total Cooling Capacity
    autosize,                 !- Low Speed Gross Rated Sensible Heat Ratio
    3.9094111254,             !- Low Speed Gross Rated Cooling COP
    autosize,                 !- Low Speed Rated Air Flow Rate
    CoilClgDXQRatio_fTwbToadbSI 1,    !- Low Speed Total Cooling Capacity Function of Temperature Curve Name
    CoilClgDXEIRRatio_fTwbToadbSI 1,    !- Low Speed Energy Input Ratio Function of Temperature Curve Name
    ,                         !- Condenser Air Inlet Node Name
    AirCooled,                !- Condenser Type
    ,                         !- Minimum Outdoor DryBulb Temperature for Compressor Operation
    0.0,                      !- High Speed Evaporative Condenser Effectiveness
    autosize,                 !- High Speed Evaporative Condenser Air Flow Rate
    autosize,                 !- High Speed Evaporative Condenser Pump Rated Power Consumption
    0.0,                      !- Low Speed Evaporative Condenser Effectiveness
    autosize,                 !- Low Speed Evaporative Condenser Air Flow Rate
    autosize,                 !- Low Speed Evaporative Condenser Pump Rated Power Consumption
    ,                         !- Supply Water Storage Tank Name
    ,                         !- Condensate Collection Water Storage Tank Name
    0.0,                      !- Basin Heater Capacity
    10.0;                     !- Basin Heater Setpoint Temperature
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answered 2020-02-18 07:10:53 -0600

When autosizing the low speed air flow rate and low speed capacity a ratio of 1/3 is used. This is hard coded into the program and cannot be changed. This is not mentioned in the Input Output Reference document but I did find it in the sizing section of the Engineering Reference.

10.7.13 DX Coil Sizing

10.7.13.13 Rated Air Volume Flow Rate, low speed
  The rated air volume flow rate, low speed, is set equal to 1/3 times the full rated air volume flow rate.
10.7.13.14 Rated Total Cooling Capacity, Low Speed
  The rated total cooling capacity, low speed, is set equal to 1/3 times the full rated total cooling capacity.
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Asked: 2020-02-16 08:21:45 -0600

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Last updated: Feb 18 '20