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7.6.1.2 Extracting Fan Power – Baseline Design
Per G3.1.2.1 [1], “where efficiency ratings, such as EER and COP, include fan energy, the descriptor shall be broken down into its components so that supply fan energy can be modeled separately.”
For baseline systems 1, 2, 3, 4, 5, and 6, calculate the minimum COPNFCOOLING and COPNFHEATING from the rated efficiencies from tables 6.8.1A, 6.8.1B, and 6.8.1D using equations 7-3 through 7-7 below. Where both part-load and full-load ratings are given in tables 6.8.1A, 6.8.1B, or 6.8.1D, use the full load rating.
COPNFCOOLING = 7.84E-8 × EER × Q + 0.338 × EER (Equation 7-3)
COPNFCOOLING = 0.0076 × SEER2 + 0.3796 × SEER (Equation 7-4)
COPNFHEATING = 1.48E-7 × COP47 × Q + 1.062 × COP47 (Equation 7-5)
COPNFHEATING = -0.026 × HSPF2 + 0.7134 × HSPF (Equation 7-6)
where
COPNFCOOLING is the adjusted cooling COP with fan power removed, to be used for simulation purposes COPNFHEATING is the adjusted heating COP with fan power removed
Q is the AHRI rated total cooling capacity of the unit (net capacity) in Btu/h*
- When using equations 7-3 and 7-5 to calculate COPNFCOOLING and COPNFHEATING in conjunction with tables 6.8.1A and 6.8.1B [1], Q shall be capped at the lower capacity of the highest capacity bracket for the applicable equipment type.
- When using equations 7-3 and 7-5 to calculate COPNFCOOLING and COPNFHEATING in conjunction with Table 6.8.1D [1] (PTAC and PTHP systems), Q shall be capped at 15,000 Btu/hand shall be no less than 7,000 btu/h.
- For the purposes of calculating COPNFCOOLING and COPNFHEATING for the baseline model, Q need only be within the 20% of the modeled system capacity (it is not required that Q exactly match the modeled capacity). This is to prevent the need for recalculating COPNFCOOLING and COPNFHEATING numerous times during the modeling process.
My Questions are,
- Whether the above points 1, 2 & 3 is acceptable to consider EIR in Baseline Energy Model?
- My current project’s baseline system is Packaged VAV and the building is G+1 with conditioned area of 60,000 sq. ft. The auto sized cooling capacity of one floor is 464,000 Btu/h(which is greater than 240,000 Btu/hand less than 760,000 Btu/h. In this case, can I use 240,000 Btu/hr instead of modelled capacity (464,000 Btu/h)?
- How the 20% limit can be arrived to calculate the adjusted EIR as per the point 3? Any method?
Please guide me.
Thanks…
Tyler Thumma
7GroupLEEDuser Expert
67 thumbs up
December 20, 2019 - 11:01 am
1. Yes these equations are acceptable to calculate the Baseline EIR values as 1/COPNFCOOLING and 1/COPNFHEATING. These equations have actually been incorporated directly into Appendix G beginning with 90.1-2013 as requirements for removing the fan energy from the Baseline efficiencies.
2. Point 3 is not included in 90.1, but I'm assuming the purpose of the 20% allowance would be to reduce the need for calculating the EIR values four times (once for each Baseline rotation). Assuming the auto-sized Baseline capacities do not differ by more than 20% by rotation, the EIR values calculated for the actual orientation would be applicable to the 90-deg, 180-deg, and 270-deg rotations.