eQuesters:

We're working on a 90.1-2007 baseline model with System 4: PSZ-HP. It's modeled as a Packaged Single Zone system with DX cooling and Heat Pump heat. Unmet hours in all zones are through the roof, around 6,000. We've gone through all our usual methods to mitigate unmet hours to no avail (zone entering temp, schedules, total airflow, zone heat source, feels like we've changed every input available?).

If the heat source is switched to electric or furnace, the unmet hours disappear. In addition, the design is a VRF system that's being modeled as a PSZ heat pump and has no unmet hours.

Has anyone run into this issue? What are we missing?

Any insight is appreciated.

Vicki Rybl, LEED AP BD+C, Fitwel Ambassador | Energy Engineer | RDK Engineers, An NV5 Company
70 Fargo Street, Suite 800 | Boston, MA 02210 | P: 857.221.5943 | F: 617.345.4226

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