Question-and-Answer Resource for the Building Energy Modeling Community
 | 1 | initial version |
electricity_cooling_kwh and electricity_heating_kwh do not include the fan energy, so you need to add them all together to get the overall energy use:
So the SEER 15/HSPF 8.5 MSHP uses 10% less energy than the SEER 15/HSPF 8.5 single-speed ASHP.
The fact that the SEER 18/HSPF 9.6 two-speed ASHP uses 7% more energy than the SEER 15/HSPF 8.5 single-speed ASHP is not too surprising. We've seen that previously and investigation showed that it was caused by increased duct losses with the two-speed equipment due to longer run times.
Note that you don't need to modify hvac_sizing.rb to override ACCA Manual S and size for maximum heating load. You can set heat_pump_capacity=autosize for max load. See the argument description here:
If using '#{Constants.SizingAuto}', the autosizing algorithm will use ACCA Manual S to set the heat pump capacity based on the cooling load. If using '#{Constants.SizingAutoMaxLoad}', the autosizing algorithm will override ACCA Manual S and use the maximum of the heating and cooling loads to set the heat pump capacity, based on the heating/cooling capacities under design conditions.
https://github.com/NREL/OpenStudio-BuildStock/blob/f3464154fb283d4cfa8a4a5e56c2ce15bf101185/resources/measures/ResidentialHVACAirSourceHeatPumpSingleSpeed/measure.rb#L190
| | 2 | No.2 Revision |
electricity_cooling_kwh and electricity_heating_kwh do not include the fan energy, so you need to add them all together to get the overall energy use:
So the SEER 15/HSPF 8.5 MSHP uses 10% less energy than the SEER 15/HSPF 8.5 single-speed ASHP.
The fact that the SEER 18/HSPF 9.6 two-speed ASHP uses 7% more energy than the SEER 15/HSPF 8.5 single-speed ASHP is not too surprising. We've seen that previously and investigation showed that it was caused by increased duct losses with the two-speed equipment due to longer run times.times. This phenomenon has been seen in field testing of variable capacity heat pumps: https://www.aceee.org/files/proceedings/2016/data/papers/1_138.pdf
Note that you don't need to modify hvac_sizing.rb to override ACCA Manual S and size for maximum heating load. You can set heat_pump_capacity=autosize for max load. See the argument description here:
If using '#{Constants.SizingAuto}', the autosizing algorithm will use ACCA Manual S to set the heat pump capacity based on the cooling load. If using '#{Constants.SizingAutoMaxLoad}', the autosizing algorithm will override ACCA Manual S and use the maximum of the heating and cooling loads to set the heat pump capacity, based on the heating/cooling capacities under design conditions.
https://github.com/NREL/OpenStudio-BuildStock/blob/f3464154fb283d4cfa8a4a5e56c2ce15bf101185/resources/measures/ResidentialHVACAirSourceHeatPumpSingleSpeed/measure.rb#L190
