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DX Cooling Coil EER and COP

asked 2017-11-05 12:56:32 -0600

fp0417 gravatar image

updated 2017-11-06 14:36:14 -0600

Hello everyone,

In my baseline (energyplus /openstudio) model. I have been entering my EER (9.8) as COP(2.872) under an input in the DX Coil named "Rated High Speed COP". But when I look at the energy plus equipment summary output tables for DX cooling coils I see a rated standard COP(w/w) output of 2.55 and a EER (Btu/W-H) of 8.71. To try and find a solution I went into the eneryplus reference material and saw that it said that the COP input is "Gross cooling capacity divided by power input to the compressor and out door fan, but DOES NOT include supply fan heat or supply fan electrical energy input." So I was not sure if if those lower COP and lower EER values in the output table would be considered (by LEED Reviewer) correct or if I should try and add the missing supply fan heat and electrical energy input so that I can increase my EER and COP values to match 90.1. Then I thought I should take another look at ASHRAE G3.1.2.1 Equipment efficiencies and saw it said " all HVAC equipment in the baseline building design shall be modeled at the minimum efficiency levels, both part load and full load, in accordance with section 6.4. Where efficiencies ratings, such as EER and COP, include fan energy, the descriptor shall be broken down into its components so that the fan energy can be modeled separately". So it sounds like I am not suppose to include my supply fan energy in my coil EER. So does that mean I need to remove the supply fan power from my 9.8 EER so that it matches the energyplus input description?

Thanks everyone

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answered 2017-12-11 21:16:02 -0600

If you look at the equipment summary output in the EnergyPlus results, you should see the nominal efficiency (in the "cooling coils" table) listed as the high speed COP, and the standard rated net COP (in the "DX cooling coils" table) as the lower value. From what I understand from the EngineeringReference, the standard rated net COP is calculated from the standard rating cooling capacity which adjusts the rated capacity to a specific temperature and flow fraction.

I don't think these values are actually used in your simulation, they are just outputted for your information (anyone feel free to correct me if I am wrong).

If you are concerned with complying with LEED, you should be removing your fan energy from your EER or COP before inputting it into your model. Refer to ASHRAE 90.1-2013 or later for an updated version of Appendix G which includes the equations to use.

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@FP___0417 did this answer your question? If so, please mark as the correct answer.

Anna Osborne Brannon gravatar imageAnna Osborne Brannon ( 2018-01-07 20:56:01 -0600 )edit

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Asked: 2017-11-05 12:56:32 -0600

Seen: 318 times

Last updated: Dec 11 '17