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Fix for 11016; Set correct water flow rate of companion cooling coils for WAHP applications using the AirloopHVAC:UnitarySystem#11017

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mitchute merged 2 commits intodevelopfrom
wahp_unit_sys_clg_flow_fix
Sep 26, 2025
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Fix for 11016; Set correct water flow rate of companion cooling coils for WAHP applications using the AirloopHVAC:UnitarySystem#11017
mitchute merged 2 commits intodevelopfrom
wahp_unit_sys_clg_flow_fix

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@lymereJ lymereJ commented Apr 1, 2025 •
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Pull request overview

Description of the purpose of this PR

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  • Title of PR should be user-synopsis style (clearly understandable in a standalone changelog context)
  • Label the PR with at least one of: Defect, Refactoring, NewFeature, Performance, and/or DoNoPublish
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@lymereJ lymereJ added the Defect Includes code to repair a defect in EnergyPlus label Apr 1, 2025
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lymereJ commented Apr 1, 2025

Water flow rate for the defect file ...

... With the current develop:
current_develop

... With this branch:
with_fix

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lymereJ commented Apr 1, 2025
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Walkthrough:

src/EnergyPlus/WaterToAirHeatPumpSimple.cc
Comment on lines -2960 to +2970
if (simpleWatertoAirHP.WAHPType == WatertoAirHP::Heating) {
PlantUtilities::RegisterPlantCompDesignFlow(
state, simpleWatertoAirHP.WaterInletNodeNum, 0.5 * simpleWatertoAirHP.RatedWaterVolFlowRate);
if (simpleWatertoAirHP.CompanionCoolingCoilNum > 0) {
auto &companionCoolingCoil(state.dataWaterToAirHeatPumpSimple->SimpleWatertoAirHP(simpleWatertoAirHP.CompanionCoolingCoilNum));
if (simpleWatertoAirHP.CompanionCoolingCoilNum > 0) {
auto &companionCoolingCoil(state.dataWaterToAirHeatPumpSimple->SimpleWatertoAirHP(simpleWatertoAirHP.CompanionCoolingCoilNum));
if (companionCoolingCoil.RatedWaterVolFlowRate > simpleWatertoAirHP.RatedWaterVolFlowRate) {
simpleWatertoAirHP.RatedWaterVolFlowRate = companionCoolingCoil.RatedWaterVolFlowRate;
} else {
companionCoolingCoil.RatedWaterVolFlowRate = simpleWatertoAirHP.RatedWaterVolFlowRate;
PlantUtilities::RegisterPlantCompDesignFlow(
state, companionCoolingCoil.WaterInletNodeNum, 0.5 * simpleWatertoAirHP.RatedWaterVolFlowRate);
}
} else if (simpleWatertoAirHP.WAHPType == WatertoAirHP::Cooling) {
PlantUtilities::RegisterPlantCompDesignFlow(
state, simpleWatertoAirHP.WaterInletNodeNum, 0.5 * simpleWatertoAirHP.RatedWaterVolFlowRate);
}
PlantUtilities::RegisterPlantCompDesignFlow(state, simpleWatertoAirHP.WaterInletNodeNum, 0.5 * simpleWatertoAirHP.RatedWaterVolFlowRate);
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This routine is called sequentially for each coil, so set the flow rate of each coil based on the larger of the two companion coils.

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This is off topic but if the Sizing:Plant object uses different delta T's shouldn't the flow rate in each operating mode be different (i.e., to actually operate at the Sizing:Plant delta T specified)? This is of course outside the scope of this issue but I think it's important to think of things like that. I guess it would be good to check manufacturers data to see if different water flow rates are ever possible or if 2-speed pumps are ever used. Using the same flow rate for cooling and heating does seem like the right choice. Although I do wonder if there are times when the first coil would post it's result to the eio before the companion coil got a chance to update the water flow rate?

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I could very well be wrong but I don't think that this issue could arise. Stepping through the debugger I see that, when we have companion coils, because the cooling coil is always evaluated first and its final capacity is only fully determined after the heating coil has been sized, I think that the process to output the flow to the EIO file is only done then (meaning after both coils have been sized) and only once.

On a different note, I see comments in the block of code above this one related to the system capacity used to determined the flow rate. I think these comments are valid: we're currently using the evaporator capacity but we should use the condenser capacity. Should a different PR be created to address these?

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I would create a different PR for changing the condenser flow sizing method.

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@mitchute mitchute Sep 25, 2025

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@rraustad anything else to look at here?

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@rraustad rraustad Sep 25, 2025

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I think this is worthy of slight pressure on the green button below.

@lymereJ lymereJ added this to the EnergyPlus 25.2 IO Freeze milestone Apr 1, 2025
@lymereJ lymereJ changed the title Fix for; Set correct water flow rate of companion cooling coils for WAHP applications using the AirloopHVAC:UnitarySystem Fix for 11016; Set correct water flow rate of companion cooling coils for WAHP applications using the AirloopHVAC:UnitarySystem Apr 1, 2025
@Myoldmopar Myoldmopar self-assigned this Apr 9, 2025
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nrel-bot-2 commented May 9, 2025

@Myoldmopar @lymereJ @Myoldmopar it has been 29 days since this pull request was last updated.

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nrel-bot-2c commented Jun 12, 2025

@Myoldmopar @lymereJ @Myoldmopar it has been 35 days since this pull request was last updated.

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nrel-bot-2 commented Jul 11, 2025

@Myoldmopar @lymereJ @Myoldmopar it has been 28 days since this pull request was last updated.

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nrel-bot-2 commented Aug 22, 2025

@Myoldmopar @lymereJ @Myoldmopar it has been 42 days since this pull request was last updated.

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nrel-bot-2 commented Sep 24, 2025

@Myoldmopar @lymereJ @Myoldmopar it has been 33 days since this pull request was last updated.

@mitchute mitchute self-requested a review September 24, 2025 18:30
@mitchute mitchute merged commit 32e2758 into develop Sep 26, 2025
8 of 9 checks passed
@mitchute mitchute deleted the wahp_unit_sys_clg_flow_fix branch September 26, 2025 01:22
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Defect Includes code to repair a defect in EnergyPlus

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EnergyPlus 25.2

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Successfully merging this pull request may close these issues.

No water flow rate during cooling operation when heating coil water flow rate is hardsized

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