This AF uses an OEM box flow coefficient (K-factor) and input from a differential pressure sensor to calculate air volume flow.

Note: Unlike Supply air VAV 12, coefficient value combines the duct area into the value. Unit of coefficient is [m3/h/SqrtPa (SI unit)] / [ft3/min/inWC (US unit)] / [l/s/SqrtPa (CA unit)].

Following is an explanation to each option under Supply air VAV 13, press, flow conv, ctr. as highlighted in the above screenshots:

Options

Details

Nominal air volume flow

Maximum air flow capacity of the VAV box. Must be no larger than 1.2 times the greater of the values of maximum air flow for ventilation or heating or cooling.

Supply air VAV flow coefficient

The value used to calibrate span of air flow measurement; the value of calc flow coefficient is written to this object upon the Calibrate command.

Supply air VAV maximum air volume flow for cooling

Maximum air flow setpoint when in cooling mode; the air flow used for balancing when the Supply air VAV balancing mode = 1.

Supply air VAV minimum air volume flow for cooling

Minimum air flow setpoint when in cooling mode; the air flow used for balancing when the Supply air VAV balancing mode = 4.

Supply air VAV maximum air volume flow for heating

Maximum air flow setpoint when in heating mode; the air flow used for balancing when the Supply air VAV balancing mode = 2.

Supply air VAV minimum air volume flow for heating

Minimum air flow setpoint when in heating mode; the air flow used for balancing when the Supply air VAV balancing mode = 5.

Supply air VAV maximum air volume flow for ventilation

Maximum ventilation air flow setpoint for indoor air quality (IAQ) controller and for Rapid ventilation; the air flow used for balancing when the Supply air VAV balancing mode = 3.

Supply air VAV minimum air volume flow for ventilation

Minimum air flow setpoint for ventilation, whether fixed or controlled by indoor air quality (IAQ) controller; see more information about minimum ventilation flow in Ventilation control. The air flow used for balancing when the Supply air VAV balancing mode = 6.

Enable monitoring for missing air volume flow (optional)

  • 0:No: Set to No to remain with pressure independent control if very low / missing air flow is detected.
  • 1:Yes: Set to Yes to switch to pressure dependent control if very low / missing air flow is detected. With Yes or No, an invalid air flow signal causes pressure dependent control.

When the measured air volume flow falls below 5% of nominal, the air volume flow is very low / missing, the function “Enable monitoring for missing air volume flow” START working, the pressure control switch to dependent control.

When the measured air volume flow rises above 7% of nominal, air volume flow back to normal, the function “Enable monitoring for missing air volume flow” STOP working, the pressure control switch back to independent control.

Note: Default setting is Yes on Apptype version 1.001 to 4.001. and No on Apptype version 5.001.