VRF is unable to meet heating demand

asked 2022-01-17 17:03:16 -0500

saahir.ga's avatar

updated 2022-01-18 09:52:06 -0500

I have been trying to implement a VRF heating/cooling system for an openstudio model of a single floor in a large residential building (~44,000 sq.ft). I am modeling the entire floor as one thermal zone (Thermal Zone 1). When I use Openstudio's default Packaged Terminal Heat Pump system to condition Thermal Zone 1, I have zero Unmet Hours, but when I use OpenStudio's VRF system (with 1 terminal connected to the one zone), the model gives ~1000 unmet heating hours. I tried adding more VRF terminals to condition the same thermal zone, which brings the unmet hours down to ~500 to 600, but does not fix the issue (all the while increasing my building's overall EUI far beyond the value achieved with the PTHP). Do you have any advice?

When I added more thermal zones to the same floor, it initially made the unmet hours decrease, but then the cooling unmet hours increased.

I also tried using the Openstudio measure (VRF with DOAS), but applying this measure resulted in my model no longer running without errors.

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