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Adding a ASHP to residential model

asked 2024-01-08 18:04:15 -0500

ahahawhut's avatar

updated 2024-01-09 08:13:29 -0500

I am building a residential model in EnergyPlus in a heating dominant climate. The model currently has DX:SingleSpeed for cooling and Coil:Heating:Fuel for heating. I would like to change the HVAC such that it is now a ASHP (preferrably min-split ducted) with the furnace as a supplement during winter months.

I've looked up product specs to build out the performance curves using the axillary programs, but am unable to figure out the node and equipment placement with the furnace in a Blow Through position. I'm also consistently getting an error for not having a defrost curve, which I know is a known error, but cannot figure out how to build this curve to appease EnergyPlus.

Please provide some guidance to resources which may help.

tl;dr : looking for examples of HVAC diagrams with ASHP system (preferably min-split ducted) with furnace as supplement and/or resources to build defrost energy input ratio function.

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answered 2024-01-11 16:56:15 -0500

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:

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Asked: 2024-01-08 18:04:15 -0500

Seen: 117 times

Last updated: Jan 11