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Modeling VRF Hot Gas Reheat (Cooling + Reheat) in EnergyPlus/OpenStudio

asked 2026-01-04 04:25:45 -0600

grandux's avatar

Hello, I am working on HVAC system modeling in EnergyPlus/OpenStudio and would appreciate some guidance.

My target system is a VRF-based system with temperature and humidity control in each zone. Dehumidification is achieved by cooling followed by reheat using compressor discharge hot gas (hot gas bypass), and the system switches between cooling-only, cooling + reheat, and fan-only modes based on preset temperature and humidity conditions.

I have a few specific questions:

VRF hot-gas reheat modeling

Is it possible in EnergyPlus/OpenStudio to explicitly model a VRF system where compressor discharge hot gas is used for a reheat coil on the air side (e.g., within a DOAS or indoor unit), or is this outside the scope of the built-in VRF models?

Recommended methods

If direct modeling is not supported, what are commonly accepted approaches to approximate VRF hot-gas reheat behavior?

Any advice, references, or example models would be greatly appreciated.

Thank you for your time.

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answered 2026-01-05 10:13:17 -0600

EnergyPlus models hot gas reheat in an air system with the Coil:Heating:Desuperheater object type. According to the documentation, the input field for the heating source does NOT include a VRF coil. The documentation could be incorrect, so it's at least trying with a test simulation.

One method you could use to model hot gas reheat with a VRF coil as the heating source would be through the Energy Management System (EMS) feature of EnergyPlus. You would have a sensor for the VRF coil's cooling energy, then use an actuator to override the heating energy delivered by the reheat coil as a function of the cooling energy sensor.

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Asked: 2026-01-04 04:25:45 -0600

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