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// CODE SNIPPET

C403.4.1 Fan Control

2015 Washington State Energy Code > 4 [CE] Commercial Energy Efficiency > C403 Building Mechanical Systems > C403.4 Hydronic and Multiple-Zone HVAC Systems Controls and Equipment. (Prescriptive) > C403.4.1 Fan Control
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AMENDMENT
This section has been amended at the state or city level.
Controls shall be provided for fans in accordance with Sections C403.4.1.1 through C403.4.1.3 C403.4.1.2.

C403.4.1.1 Fan Airflow Control

AMENDMENT
This section has been amended at the state or city level.

Each cooling system listed in Table C403.4.1.1 shall be designed to vary the indoor fan airflow as a function of load and shall comply with the following requirements:

  1. Direct expansion (DX) and chilled water cooling units that control the capacity of the mechanical cooling directly based on space temperature shall have not fewer than two stages of fan control. Low or minimum speed shall not be greater than 66 percent of full speed. At low or minimum speed, the fan system shall draw not more than 40 percent 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.
  2. 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 be not greater than 50 percent of full speed. At minimum speed the fan system shall draw not more than 30 percent of the power at full fan speed. Low or minimum speed shall be used during periods of low cooling load and ventilation-only operation.
  3. Units that include an airside economizer in accordance with Section C403.3 shall have not fewer than two speeds of fan control during economizer operation

Exceptions:

  1. Modulating fan control is not required for chilled water and evaporative cooling units with fan motors of less than 1 hp (0.746 kW) where the units are not used to provide ventilation air and the indoor fan cycles with the load.
  2. Where the volume of outdoor air required to comply with the ventilation requirements of the International Mechanical Code at low speed exceeds the air that would be delivered at the speed defined in Section C403.4.1, the minimum speed shall be selected to provide the required ventilation air.

TABLE C403.4.1.1

EFFECTIVE DATES FOR FAN CONTROL

COOLING
SYSTEM TYPE
FAN
MOTOR SIZE
MECHANICAL
COOLING CAPACITY
DX coolingAny≥ 75,000 Btu/h
(before 1/1/2016)
≥ 65,000 Btu/h
(after 1/1/2016)
Chilled water and
evaporative cooling
≥ 5 hpAny
≥ 1/4 hpAny

For SI: 1 British thermal unit per hour = 0.2931 W; 1 hp = 0.746 kW.

C403.4.1.1 Static Pressure Sensor Location

AMENDMENT
This section has been amended at the state or city level.
Static pressure sensors used to control VAV fans shall be located such that the controller setpoint is no greater than 1.2 inches w.c. (2099 Pa). Where this results in one or more sensors being located downstream of major duct splits, not less than one sensor shall be located on each major branch to ensure that static pressure can be maintained in each branch.

Exception: Systems complying with Section C403.4.1.2.

C403.4.1.2 Static Pressure Sensor Location

AMENDMENT
This section has been amended at the state or city level.
Static pressure sensors used to control VAV fans shall be located such that the controller set point is not greater than 1.2 inches w.c. (299 Pa). Where this results in one or more sensors being located downstream of major duct splits, not less than one sensor shall be located on each major branch to ensure that static pressure can be maintained in each branch.

C403.4.1.2 Set Points for Direct Digital Control

AMENDMENT
This section has been amended at the state or city level.
For systems with direct digital control of individual zones reporting to the central control panel, the static pressure setpoint shall be reset based on the zone requiring the most pressure. In such cases, the set point is reset lower until one zone damper is nearly wide open. The direct digital controls shall be capable of monitoring zone damper positions or shall have an alternative method of indicating the need for static pressure that is configured to provide all of the following:
  1. Automatically detecting any zone that excessively drives the reset logic.
  2. Generating an alarm to the system operational location.
  3. Allowing an operator to readily remove one or more zones from the reset algorithm.

C403.4.1.3 Set Points for Direct Digital Control

AMENDMENT
This section has been amended at the state or city level.

For systems with direct digital control of individual zones reporting to the central control panel, the static pressure set point shall be reset based on the zone requiring the most pressure. In such case, the set point is reset lower until one zone damper is nearly wide open. The direct digital controls shall be capable of monitoring zone damper positions or shall have an alternative method of indicating the need for static pressure that is capable of all of the following:

  1. Automatically detecting any zone that excessively drives the reset logic.
  2. Generating an alarm to the system operational location.
  3. Allowing an operator to readily remove one or more zones from the reset algorithm.

Related Code Sections


C403.8.5 [CE] Commercial Energy Efficiency, Fan Controls
Controls shall be provided for fans in accordance with Section C403.8.5.1 and as required for specific systems provided in Section C403 ...
2018 Washington State Energy Code - Commercial Provisions > 4 [CE] Commercial Energy Efficiency > C403 Mechanical Systems > C403.8 Fan and Fan Controls > C403.8.5 Fan Controls
C403.8.1 [CE] Commercial Energy Efficiency, Allowable Fan Motor Horsepower
health and safety or environmental control shall be permitted to use variable volume fan power limitation. Individual exhaust fans with motor ...
2018 Washington State Energy Code - Commercial Provisions > 4 [CE] Commercial Energy Efficiency > C403 Mechanical Systems > C403.8 Fan and Fan Controls > C403.8.1 Allowable Fan Motor Horsepower
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