Question-and-Answer Resource for the Building Energy Modeling Community
 | 1 | initial version |
Assuming the ducted mini-split and furnace are sharing the same distribution system and blower, you can model the mini-split using the AirLoopHVAC:UnitarySystem object (with MultiSpeed or VariableSpeed DX heating/cooling coils) and then describe the furnace using a Coil:Heating:Fuel that's assigned to the UnitarySystem's Supplemental Heating Coil. The supplemental coil will provide heating whenever the DX heating coil has insufficient capacity compared to the building's heating load.
You might also set the Minimum Outdoor Dry-Bulb Temperature for Compressor Operation field for the DX heating coil if the mini-split cannot operate below certain temperatures, in which case the supplemental coil will provide heating during those situations as well.
Here is an example IDF w/ this kind of setup:
https://drive.google.com/file/d/1EzdsiqMXV0OqPuZoSFC9XUusi9QLHvki/view?usp=sharing
