Humidity control in split air conditioner (heat pump)

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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.