# Supply Air Fan

## System

<figure><img src="/files/PCaB9jUneaFJSF3Zu3I3" alt=""><figcaption></figcaption></figure>

### Fan Speed Method

Specify the Fan Speed Method by choosing between Continuous or Discrete. Discrete implies specific speed settings, while Continuous allows smooth variation up to the Design Maximum Air Flow Rate.

Discrete control uses time-weighted averaging, and Variable control uses flow-weighted averaging. For constant volume or on-off fans, select Discrete with Number of Speeds set to 1. Variable air volume fans should use Continuous, requiring a fan performance curve in the input field named Electric Power Function of Flow Fraction Curve Name.

### Fan Motor Efficiency

Specify the Fan Motor Efficiency by entering a value for motor efficiency - the ratio of shaft power to electric power consumed by the motor.

### Fan Motor In Air Stream Fraction

Specify the Fan Motor In Air Stream Fraction as the fraction of motor heat added to the air stream. A value between 0 and 1 is accepted, where 0 means the motor is outside the air stream with no added heat, and 1 means the motor is entirely inside, adding all of its heat to the air stream.

## Sizing

<figure><img src="/files/GBNw2aGEADiJPkr4CF4i" alt=""><figcaption></figcaption></figure>

### Fan Design Power Sizing Method

Specify the Fan Design Power Sizing Method by choosing from:

**Power Per Flow:** For Power Per Flow, use the Electric Power Per Unit Flow Rate to size the Design Electric Power Consumption.

**Power Per Flow Per Pressure:** For Power Per Flow Per Pressure, the Electric Power Per Unit Flow Rate Per Unit Pressure is used for sizing.

**Total Efficiency And Pressure:** For Total Efficiency And Pressure, use the input Fan Total Efficiency and Design Pressure Rise to size the power.

### Fan Total Efficiency

Specify the Fan Total Efficiency by entering a value for motor efficiency - the ratio of shaft power to electric power consumed by the motor.

### Fan Design Pressure Rise

Specify the Fan Design Pressure Rise as the total system pressure rise experienced by the fan in Pascals at full flow rate and altitude-adjusted standard density of dry air at 20 degrees Celsius dry bulb.

### Sizing Method

Choose the Sizing Method by selecting from Autosize or Manual.

### Fan Design Maximum Air Flow Rate

Specify the Fan Design Maximum Air Flow Rate as the numeric field for the design volume flow rate of the fan in the HVAC system, in m3/s. This full-speed flow rate serves as the upper limit for fans capable of varying their flow rate and can be autosized.

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