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System fan electrical power for supply, return, exhaust, and relief (excluding power to fan-powered VAV boxes) shall be calculated using the following formulas:
For Systems 1 and 2,
Pfan = CFMs × 0.3
For Systems 3 through 8, and 11, 12, and 13,
Pfan = bhp × 746/fan motor efficiency
For Systems 9 and 10 (supply fan),
Pfan = CFMs × 0.3
For Systems 9 and 10 (non-mechanical cooling fan if required by Section G3.1.2.8.2),
Pfan = CFMnmc × 0.054
where
Pfan = electric power to fan motor, W
bhp = brake horsepower of baseline fan motor from Table G3.1.2.9
fan motor efficiency = the efficiency from Table G3.9.1 for the next motor size greater than the bhp
CFMs = the baseline system maximum design supply fan airflow rate, cfm
CFMnmc = the baseline non-mechanical cooling fan airflow, cfm
Baseline Fan Motor Brake Horsepower
Constant-Volume Systems 3, 4, 12, and 13 Variable-Volume Systems 5 to 8 Variable-Volume System 11
CFMs × 0.00094 + A CFMs × 0.0013 + A CFMs × 0.00062 + A
Notes:
  1. Where A is calculated according to Section 6.5.3.1.1 using the pressure-drop adjustment from the proposed design and the design flow rate of the baseline building system.
  2. Do not include pressure-drop adjustments for evaporative coolers or heat recovery devices that are not required in the baseline building system by Section G3.1.2.10.
G3.1.2.9.1
The calculated system fan power shall be distributed to supply, return, exhaust, and relief fans in the same proportion as the proposed design.

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