packaged equipment fan energy

asked 2018-06-13 13:30:57 -0500

Matt Koch's avatar

updated 2018-06-13 13:40:29 -0500

So, I am aware that most compliance codes/standards require breaking out fan energy consumption from packaged equipment energy consumption. Notably, in OpenStudio, if the packaged equipment has a an overall COP, then the DX coil in the Air Loop should have a modified no-fan COP, and the fan in the air loop should have its own efficiency parameters. Maybe something like the following, or perhaps using ASHRAE 90.1-2013 Appendix G3.1.2.1.

COP_no-fan = 1/(1/COP + P_fan/Q)
P_fan = dp*V/e_ele/e_mec/6356*2544.43 (BTU/h)/HP

Here, dp is fan static pressure rise [inWC], V is fan flow rate [cfm], e_mec is fan mechanical efficiency [1], e_ele is fan electrical efficiency [1], and Q is cooling capacity [BTU/h], all at the design or rated point.

However, what if I do not care about breaking out fan energy? Can I then just assign the overall COP to the DX coil of the Air Loop, and simply set dp = 0 inWC, so the fan does not accumulate energy separately from the DX coil? Also, would this not lead to a more accurate energy estimation because I avoid the uncertainty of the fan energy break out?

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