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How replace autosized values with equivalent hardsize values for heating coils

asked 2019-05-29 19:33:43 -0500

updated 2019-06-05 11:57:05 -0500

I'm trying to convert my EnergyPlus model from autosize values to hard sized values so that sizing wont change with subsequent runs. I've replaced all autosized fields with data from the EIO file, however I'm getting different results.

I've noticed quite different reported coil sizes for the Coil:Heating:Water object, between the autosized and hardsized version. I've tried two approaches and neither work:

1) Replace all fields which were autosize with values from EIO:

  • U-Factor Times Area Value, Maximum Water Flow Rate, Rated Capacity
  • In the EIO there are two Capacity values given: "Design Size Rated Capacity [W]" (under component sizing info) AND "Nominal Total Capacity {W}" (under Water Heater Coil Capacity Info)
  • I've tried both and neither result in a coil size that matches the autosize file (based on comparing EIO files and HTML files)

2) Input Rated Capacity Only:

  • changed Performance Input Method to nominalcapacity
  • this causes energyplus to crash or tell me I need a sizing object, depending on whether I leave UA blank or put autosize

This seems like it should be pretty easy to do, but I'm quite confused about what E+ is doing between input capacity and the final coil size it uses. I appreciate any insight on this! Using E+ v 9.1

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answered 2019-06-11 17:04:03 -0500

Use the UFactorTimesAreaAndDesignWaterFlowRate method and autosize the UA and water flow rate. Then use the autosized value for these two fields. That should be all that's necessary.

From the 5ZoneAirCooled example file:

Coil:Heating:Water,
SPACE1-1 Zone Coil,      !- Name
ReheatCoilAvailSched,    !- Availability Schedule Name
autosize,                !- U-Factor Times Area Value {W/K}
autosize,                !- Maximum Water Flow Rate {m3/s}
SPACE1-1 Zone Coil Water In Node,  !- Water Inlet Node Name
SPACE1-1 Zone Coil Water Out Node,  !- Water Outlet Node Name
SPACE1-1 Zone Coil Air In Node,  !- Air Inlet Node Name
SPACE1-1 In Node,        !- Air Outlet Node Name
UFactorTimesAreaAndDesignWaterFlowRate,  !- Performance Input Method

The eio output for this coil:

Component Sizing Information, Coil:Heating:Water, SPACE1-1 ZONE COIL, Design Size Rated Capacity [W], 4624.09792
Component Sizing Information, Coil:Heating:Water, SPACE1-1 ZONE COIL, Design Size Maximum Water Flow Rate [m3/s], 1.02164E-004
Component Sizing Information, Coil:Heating:Water, SPACE1-1 ZONE COIL, Design Size U-Factor Times Area Value [W/K], 113.24397
! <Water Heating Coil Capacity Information>,Component Type,Name,Nominal Total Capacity {W}
Water Heating Coil Capacity Information,Coil:Heating:Water,SPACE1-1 ZONE COIL,3748.67

Revised SPACE1-1 Zone Coil object with hard values - only the flow rate and UA (Rated Capacity input is ignored for this performance method):

Coil:Heating:Water,
SPACE1-1 Zone Coil,      !- Name
ReheatCoilAvailSched,    !- Availability Schedule Name
113.24397,                !- U-Factor Times Area Value {W/K}
1.02164E-004,                !- Maximum Water Flow Rate {m3/s}

The eio output for the hard-sized coil:

! <Water Heating Coil Capacity Information>,Component Type,Name,Nominal Total Capacity {W}
Water Heating Coil Capacity Information,Coil:Heating:Water,SPACE1-1 ZONE COIL,3748.67

The same nominal capacity as the autosized case. This should be reliable for Coil:Heating:Water. And the simulation results are the same for these two runs.

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Asked: 2019-05-29 19:33:43 -0500

Seen: 136 times

Last updated: Jun 11