ASHRAE-90.1-2022- - Page 093
Extracted Content
6.5.3 Air System Design and Control 6.5.3.1 Fan System Power and Efficiency 6.5.3.1.1 Each HVAC system having a total fan system motor nameplate horsepower exceeding 5 hp at fan system design conditions shall not exceed the allowable fan system motor nameplate horsepower (Option 1) or fan system bhp (Option 2) as shown in Table 6.5.3.1-1. This includes supply fans, return/relief fans, exhaust fans, and fan-powered terminal units associated with systems providing heating or cooling capability that operate at fan system design conditions . Single-zone VAV systems shall comply with the constant-volume fan power limitation.
Exceptions to 6.5.3.1.1:
- Hospital, vivarium, and laboratory systems that use flow control devices on exhaust and/or return to maintain space pressure relationships necessary for occupant health and safety or environmental control may use variable-volume fan power limitation.
- Individual exhaust fans with motor nameplate horsepower of 1 hp or less.
6.5.3.1.2 Fan Motor Selection
a. For each fan less than 6 bhp, the selected fan motor shall be no larger than the first available motor with
a nameplate rating greater than 1.5 times the fan bhp . b. For each fan 6 bhp and larger, the selected fan motor shall be no larger than the first available motor with
a nameplate rating greater than 1.3 times the fan bhp .
The fan bhp must be indicated on the design documents to allow for compliance verification by the building official .
Exceptions to 6.5.3.1.2:
- Motors equipped with electronic speed control devices to vary the fan airflow as a function of load.
- Systems complying with Section 6.5.3.1.1 Option 1.
- Fans with motor nameplate horsepower of less than 1 hp.
- Fans with a fan nameplate electrical input power of less than 0.89 kW .
6.5.3.1.3 Fan Efficiency. Each fan and fan array shall have a fan energy index (FEI) of 1.00 or higher at its highest design airflow rate. Each fan and fan array used for a variable-air-volume system that meets the requirements of Section 6.5.3.2.1 shall have an FEI of 0.95 or higher at its highest design airflow rate. The FEI for fan arrays shall be calculated in accordance with AMCA 208 Annex C.
Exceptions to 6.5.3.1.3:
- Fans that are not embedded fans with a motor nameplate horsepower of less than 1.0 hp or with a fan nameplate electrical input power of less than 0.89 kW .
- Embedded fans and fan arrays with a combined motor nameplate horsepower of 5 hp or less or with a fan system electrical input power of 4.1 kW or less.
- Embedded fans that are part of equipment listed under Section 6.4.1.1.
- Embedded fans included in equipment bearing a third-party-certified seal for air performance or energy performance of the equipment package.
- Ceiling fans.
- Fans used for moving gases at temperatures above 482°F.
- Fans used for operation in explosive atmospheres.
- Reversible fans used for tunnel ventilation .
- Fans outside the scope of AMCA 208.
- Fans when operating during emergency conditions.
6.5.3.2 Fan Control 6.5.3.2.1 Supply Fan Airflow Control. Each cooling system listed in Table 6.5.3.2.1 shall be designed to vary the supply fan airflow as a function of load and shall comply with the following requirements:
a. DX and chilled-water cooling units that control the capacity of the mechanical cooling directly based on
space temperature shall have a minimum of two stages of fan control. Low or minimum speed shall not exceed 66% of full speed. At low or minimum speed, the fan system shall draw no more than 40% of the fan power at full fan speed. Low or minimum speed shall be used during periods of low cooling load and ventilation -only operation. b. All other units, including DX cooling units and chilled-water units that control the space temperature by
modulating the airflow to the space, shall have modulating fan control. Minimum speed shall not exceed
ANSI/ASHRAE/IES Standard 90.1-2022 (I-P) 91