// CODE SNIPPET
503.2.10.1 Allowable Fan Horsepower
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Each HVAC system at fan system design conditions shall not exceed the allowable fan system motor nameplate hp (Option 1) or fan system bhp (Option 2) as shown in Table 503.2.10.1(1). This includes supply fans, return/relief fans, and fan-powered terminal units associated with systems providing heating or cooling capability.
For SI: 1 cubic foot per minute = 0.0004719 m3/s, 1 horsepower = 756 W.
- Hospital and laboratory systems that utilize flow control devices on exhaust and/or return to maintain space pressure relationships necessary for occupant health and safety or environmental control shall be permitted to use variable volume fan power limitation.
- Individual exhaust fans with motor nameplate horsepower of 1 hp (0.75 kW) or less.
- Fans exhausting air from fume hoods. (Note: If this exception is taken, no related exhaust side credits shall be taken from Table 503.2.10.1(2) and the Fume Exhaust Exception Deduction must be taken from Table 503.2.10.1(2).
|LIMIT||CONSTANT VOLUME||VARIABLE VOLUME|
|Option 1: Fan system motor nameplate hp||Allowable nameplate motor hp||hp ≤ CFMS *0.0011||hp ≤ CFMs *0.0015|
|Option 2: Fan system bhp||Allowable fan system bhp||bhp ≤ CFMS *0.00094 + A||bhp ≤ CFMS *0.0013 + A|
|CFMS||=||The maximum design supply airflow rate to conditioned spaces served by the system in cubic feet per minute.|
|hp||=||The maximum combined motor nameplate horsepower.|
|bhp||=||The maximum combined fan brake horsepower.|
|A||=||Sum of [PD x CFMD / 4131].|
|PD||=||Each applicable pressure drop adjustment from Table 503.2.10.1(2) in. w.c.|
|Fully ducted return and/or exhaust air systems||0.5 in w.c.|
|Return and/or exhaust airflow control devices||0.5 in w.c.|
|Exhaust filters, scrubbers or other exhaust treatment..||The pressure drop of device calculated at fan system design condition.|
|Particulate filtration credit: MERV 9 thru 12||0.5 in w.c.|
|Particulate filtration credit: MERV 13 thru 15||0.9 in w.c.|
|Particulate filtration credit: MERV 16 and greater and electronically enhanced filters||Pressure drop calculated at 2x clean filter pressure drop at fan system design condition.|
|Carbon and other gas-phase air cleaners||Clean filter pressure drop at fan system design condition.|
|Heat recovery device||Pressure drop of device at fan system design condition.|
|Evaporative humidifier/cooler in series with another cooling coil||Pressure drop of device at fan system design conditions|
|Sound attenuation section||0.15 in w.c.|
|Fume hood exhaust exception (required if Section 503.2.10.1, Exception 3, is taken)||-1.0 in w.c.|