// CODE SNIPPET
E 503.5.6.1.1 Motor Nameplate Horsepower
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For each fan, the selected fan motor shall be not larger than the first available motor size more than the brake horsepower (bhp) (kW). The fan brake horsepower shall be indicated on the design documents to allow for compliance verification by the Authority Having Jurisdiction.
TABLE E 503.5.6.1(1) FAN POWER LIMITATION*
[ASHRAE 90.1:TABLE 6.5.3.1-1]
| 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 |
For SI units: 1 horsepower = 0.746 kW, 1 cubic foot per minute = 0.00047 m3/s
* Where:
| CFMS | = | the maximum design supply airflow rate to conditioned spaces served by the system in cubic feet per minute (m3/s) |
| hp | = | the maximum combined motor nameplate horsepower (kW) |
| bhp | = | the maximum combined fan brake horsepower (kW) |
| A | = | sum of (PD × CFMD/4131) |
| PD | = | each applicable pressure drop adjustment from Table E 503.5.6.1(2) in inch water column (kPa) |
| CFMD | = | the design airflow through each applicable device from Table E 503.5.6.1(2) in cubic feet per minute (m3/s) |
Exceptions:
- For fans less than 6 bhp (4.5 kW), where the first available motor larger than the bhp (kW) has a nameplate rating within 50 percent of the bhp (kW), the next larger nameplate motor size shall be selected.
- For fans 6 bhp (4.5 kW) and larger, where the first available motor larger than the bhp (kW) has a nameplate rating within 30 percent of the bhp (kW), the next larger nameplate motor size shall be selected.
- Systems that are in accordance with Section E 503.5.6.1, Option 1.
- Fans with motor nameplate horsepower of less than 1 hp (0.7 kW). [ASHRAE 90.1:6.5.3.1.2]