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Heatpump Calcs in Beopt

asked 2023-07-19 15:22:25 -0500

cmui's avatar

updated 2023-07-19 16:48:25 -0500

I'm looking at the new heatpump input options for Beopt 3.0.1. There is no longer a field for putting in the performance and capacity at cold temps - how is beopt calculating the cold temperature capacity of the system?

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answered 2023-07-19 16:58:18 -0500

updated 2023-07-19 16:59:02 -0500

The upcoming version of BEopt (3.1.0), expected next month, will include a number of new heat pump inputs, including heating capacity retention for both mini-split and central air source heat pumps. It will also have some updated performance curves and assumptions, particularly for variable speed heat pumps.

It will look something like this: image description

The default heating capacity retention fractions in BEopt 3.0.1 are:

  • ASHP, 1-speed: 0.45
  • ASHP, 2-speed: 0.4
  • ASHP, var-speed: 0.5
  • MSHP, var-speed: 0.4

They will change a bit in BEopt 3.1.0.

That said, note that for a given rated HSPF, the heating capacity retention fraction will generally not have a significant effect on annual energy consumption because a higher fraction will result in a lower heat pump COP in order to achieve the specified rated performance. However, a higher retention fraction can result in a significantly smaller heat pump capacity, and therefore cost, for simulations with autosized equipment.

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Got it, thanks! Will users need to input COP at part load capacity as in beopt 2.8?

cmui's avatar cmui  ( 2023-07-20 14:47:25 -0500 )edit

No, they will not.

shorowit's avatar shorowit  ( 2023-07-20 14:50:43 -0500 )edit

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Asked: 2023-07-19 15:22:25 -0500

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Last updated: Jul 19 '23