DX unit EER and Fan Power

Steven Er

LEEDuser Basic Member

8 thumbs up

June 19, 2012

Hi, I understand EER of DX unit from ASHRAE 90.1 include indoor fan power. Compressor and condenser fan power shall be derived from EER that subtracting indoor fan power. For a baseline system, fan power shall be derived according G3.1.2.9 in ASHRAE 90.1 2007. This calculated fan power seems to result a better cooling system COP (cooling provided by the compressor and condenser). Any idea about this?

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Joseph Lewis

Senior Energy Modeler

Fortier Engineering

LEEDuser Basic Member

2 thumbs up

Thu, 07/12/2012 - 20:27

What I have done is take the efficiency from the Section 6 tables, calculate the total power based on the design cooling load, calculate the fan power that would have been used in the ARI testing, subtract this power off the total, add back in the fan power calculated using G3.1.2.9, and then convert back to an efficiency value to be put in manually into my modeling software. A couple of days ago I discovered the Rocky Mountain Institute offers a free spreadsheet that guides you through this entire calculation. It is called "Energy Model Input Translator". I have only done limited in house testing, but the calculation is consistent with what I have submitted for past projects.

Steven Er

LEEDuser Basic Member

8 thumbs up

Wed, 07/18/2012 - 02:01

Joseph, thanks for sharing your experience.

Steven Er

LEEDuser Basic Member

8 thumbs up

Fri, 08/03/2012 - 09:29

Hi Joseph, I run through the "Energy Model Input Translator" from RMI. The baseline compressor COP calculation from RMI guide seems pretty logic. Any comment from GBCI reviewer on this methodology so far?