High airlfow and fan sizing eQuest, Build 7175

asked 2021-02-19 20:47:17 -0500

Jacob's avatar

updated 2021-03-29 08:59:36 -0500

Greetings Modelers, I'm working on a model for Appendix G (LEED) baseline modeling and just getting started in wizard mode (eQuest 3.65 Build 7175 and DOE2.3). When I change from PSZ Dx + Furnace to PSZ heat pump system type, my autozised airflows, fan power, and fan energy usage all go up by about 30x! The sizing for the furnace system seems reasonable, but the heat pump sizing is way off (50 cfm/sf for some zones). Both versions of the model have 1 in wg static for fan sizing and airflow autosizing at 1.0 safety factor in the wizard and the same cooling/heating design temps. I have done many similar models with eQuest build 7173 with no such issues, but the proposed model will have VRF conditioning, so I wanted to go to Build 7175 for that functionality.

I tried switching between a packaged single zone heat pump and split system heat pump system types without significant change. I tried taking the gas heat model with reasonable airflow sizing into detailed edit mode and then switching the heat source to heat pump (no other changes) and the airflow sizing issues showed up.

Any thoughts? Have you all found Build 7175 to be a generally well-functioning software package like Build 7173 is? Looks like I can't upload .pd2 or .inp (or .txt) files on this forum.

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Looks like it might be an issue with the PSZ system type. When I switch to heat pump (residential) with PVVT sizing goes back to normal.

Jacob's avatar Jacob  ( 2021-02-23 13:06:14 -0500 )edit

For what it's worth, I just encountered the same issue. This does appear to be a sizing bug in eQUEST with DOE2.3. In the SV-C reports, the design day peak loads are the same with either furnace, electric resistance or heat pump, but the design capacity is set at 27x higher for the heat pump.

Erik Kolderup's avatar Erik Kolderup  ( 2021-04-14 17:08:42 -0500 )edit