Multi-speed Fan (staged Air flow control) for ZoneHVAC:WaterToAirHeatPump

[TiejunWu]

Issue overview

Currently many of the Water to Air Heat Pump units in the market are equipped with multi-stage compressor and ECM fan to reduce energy use and noise. During actual operation, the fan air flow is coordinated with the compressor stage control, at low compression stage, the fan is going to run at low air flow rate. We propose to add supply air flow ratio input fields (low, medium, high) to object ZoneHVAC:WaterToAirHeatPump. In simulation, for each time step, cycle the fan air flow between to adjacent speeds based on the cooling / heating capacity (or coordinate with the cooling / heating coil stage for variable speed water to air coils).

Background information

Many of the Water Source Heat Pump manufacturers have adopted ECM controlled fan to achieve better humidity control, reduced fan power and noise at low load conditions. Adding multi-speed fan modeling capabilities to the EnergyPlus WSHP terminal unit object would allow engineers to demonstrate the energy performance benefits of this feature. This feature would have application for many Water to Air Heat Pump manufacturer’s products and across many market verticals.

Reference Links

1. https://www.shareddocs.com/hvac/docs/1005/Public/08/50PT-12PD.pdf Carrier - on page 28, it mentioned a 3-speed fan control and the control sequence during cooling and heating operation.
2. https://files.climatemaster.com/TY_Unit_Spec.doc ClimateMaster - on Page 7, it mentioned about coordinating the fan air flow speed with compressor stage.
3. https://tahoeweb.daikinapplied.com/api/general/DownloadDocumentByName/media/CAT_1114-12_WS_SS_GTH-GTV_026-072_LR.pdf/ Daikin - on page 7, it mentioned that unit will operate at lower fan speed under part load to reduce noise, energy and operating cost.

   Details

   Some additional details for this issue (if relevant):

   • Platform (Operating system, version)
   • Version of EnergyPlus (if using an intermediate build, include SHA)
   • Unmethours link or helpdesk ticket number

Checklist

Add to this list or remove from it as applicable. This is a simple templated set of guidelines.

• [ ] Defect file added (list location of defect file here)
• [ ] Ticket added to Pivotal for defect (development team task)
• [ ] Pull request created (the pull request will have additional tasks related to reviewing changes that fix this defect)

[mjwitte]

I believe this can be accomplished with the current AirLoopHVAC:UnitarySystem which can be used as zone equipment with Fan:SystemModel, Coil:Heating/Cooling:WaterToAirHeatPump:VariableSpeedEquationFit, and UnitarySystemPerformance:Multispeed.