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Humidity control in split air conditioner (heat pump)

asked 2016-02-17 04:45:54 -0500

Xandrika gravatar image

I am using AirLoopHVAC UnitaryHeatpump AirToAir to represent a small split air conditioner in my model. By default the Dehumidification Control Type is put None which means latent loads are not considered. However, my location has a hot and humid summer. So, I was wondering how to represent the humidity control of such a split air conditioner in Energyplus.

I guess, Dehumidification Control Type should be CoolReheat. Is this right? Consequently, I must set a ZoneControl:Humidistat object. But which maximum humidity is assumed?

A further needed input is the ´Supplemental Heating Coil Object Type´. I guess it should be electric, right?

Furthermore, the AirLoopHVAC UnitaryHeatpump AirToAir has a field called ´Supplemental Heating Coil Object Type´. Is this relevant for Dehumidification Control? Which value should be set?

Thanks a lot.

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answered 2016-02-17 10:33:40 -0500

Which Dehumidification Control Type to use?

Depends upon your cooling coil arrangement. If it's just a DX heat pump coil, then use CoolReheat to sensibly "over-cool" in order to dehumidify, then reheat. If the DX heat pump coil has a separate heat exchanger to assist with dehumidification, then use Multimode (only works if using CoilSystem:Cooling:DX:HeatExchangerAssisted in the unitary system).

How to set up ZoneControl:Humidistat to control dehumidification?

The ZoneControl:Humidistat object measures relative humidity (RH) in a zone and sends a signal requesting dehumidification when the RH goes above the RH setpoint schedule. There is an EnergyPlus example file called HeatPumpAirToAirWithRHcontrol.idf which uses the same AirLoopHVAC:UnitaryHeatPump:AirToAir object with a humidistat. Use this as a reference for how to set up your model. This example file uses a constant 50% RH setpoint, but you can change that to whatever constant value or schedule of values you desire.

What Supplemental Heating Coil Object Type to use?

Depends upon what kind of supplemental reheat coil is in the system you're modeling. If you just want a working model, the ELECTRIC and GAS heating coils are easier to set up, since they don't connect to plant loops like hot water or steam. The type of coil doesn't affect dehumidification control or how much heating energy is provided, it affects the type of energy resource consumed to provide heating energy to the supply air stream.

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@Aaron Boranian, thanks a lot for the tips. Unfortunately, I cannot find any information about how the dehumidifaction control of these types of Split Air Conditioners works. The manufacturer label it "Monsoon Comfort" or Healthy Dehumidification Operation Mode: If you select the dehum.mode on the operation selection button, the airconditioner starts to run the dehum. function, automatically setting the room temp. and airflow volume to the best condition for dehumidification based on the sensed current room temp.

Xandrika gravatar image Xandrika  ( 2016-02-17 14:53:30 -0500 )edit

@Aaron Boranian, do those wall mounted split units have any active dehumidification control? Is latent load considered in the energy consumption of the AirLoopHVAC UnitaryHeatpump AirToAir object when Dehumidification Control Type set to None?

Xandrika gravatar image Xandrika  ( 2016-02-17 14:57:36 -0500 )edit

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Asked: 2016-02-17 04:45:54 -0500

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Last updated: Feb 17 '16