Has anyone observed a big difference between SEER/HSPF reported in the Equipment Summary report ( E+/Design Builder) and rated SEER/HSPF ?
I typically enter COP, adjusted by removing fan energy per the equations in Section 11 of ASHRAE Std 90.1-2019. Or, when information is available, I use manufacturers data to calculate COP as a ratio of the cooling capacity and system power, where system power includes only outdoor fan and compressor, at rated conditions.
Either way, the Equipment Summary always reports SEER /HSPF much lower than the rated equipment SEER/HSPF. The difference is significant. For example, a heat pump rated at 16 SEER/ 8.0 HSPF would show up in the Equipment Summary as having less than 12 SEER/5.5 HSPF.
I derived performance curves for several Heat Pumps, but this did not close the gap or mitigate the issue.
Based on conversation with Design Builder support, at some point I believed this may have to do with weather file. However, whatever weather file (location) I run, my SEER/HSPF in the Equipment Summary are always significantly lower than the rated values.
Could someone explain why this might be happening?
Residential projects that I work on typically use Heat Pumps for apartments conditioning (150-300 Heat Pumps per building), so obviously this discrepancy may have a big impact on the energy results for this type of projects.
Any insight, recommendation, comments you could provide would be much appreciated!
Anna
