Addendum bl for ASHRAE 90.1-2010 provides a methodology (with equations) for removing fan energy from packaged equipment efficiency ratings for the baseline, which is very useful. However, when using the provided equations and the mandated EER from Table 6.8.1A for air-cooled air conditioners, I get a pretty substantial equipment efficiency increase for larger equipment sizes. For example, if the provided equations are used for air cooled air conditioners with "all other" heating type for different sizes, this is what I get for COPnf:

  • 100 kbtu/h: 11.0 EER, 3.80 COPnf
  • 200 kbtu/h: 10.8 EER, 3.82 COPnf  
  • 500 kbtu/h: 9.8 EER, 3.70 COPnf
  • 760 kbtu/h: 9.5 EER, 3.78 COPnf
  • 10,000 kbtu/h: 9.5 EER, 10.66 COPnf

For the 10,000 kbtu/h system, the mandated EER is 9.5, but the COPnf is 10.66, which is a higher efficiency than what a centrifugal water-cooled chiller of a similar size would need to be (COP 6.17). This seems like an oversight when the formulas were created and provided in the addendum.

Has this been encountered before? And is there an acceptable way to get a more sensible COP for larger sized baseline HVAC systems with DX cooling?

Thank you!

Joanne Choi