High limit duct static pressure control

Optional a duct static high limit pressure sensor can be used to prevent damage to ducts, dampers and air terminal units. The sensor must be mounted close to the high pressure side of the supply fan. Damage can occur when fire or smoke dampers in the supply duct close or ducts are blocked, especially during initial system start-up. The high-limit safety control will modulate the fan to limit its output to a maximum duct static pressure. This maximum setpoint is defined by parameter DSH-01. The proportional band and the integral time of this high limit safety control are respectively defined by parameter DSH-02 and DSH-03.


The integral action of the duct static pressure controller will not wind-up during override by the high limit duct static pressure control.

Depending on the value of DSH-03, it is possible that this high limit control acts as a P- or as a PI-controller. When an integral action is used, the proportional band is located above the setpoint. When no integral action is used, the proportional band is located below the setpoint.


The next figure shows the internal control signal of the duct static high pressure limit safety control, in relation to its setpoint and proportional band.



Description

Default value

DSH-01: setpoint high limit static pressure control

10000 Pa

DSH-02: P-band high limit static pressure control

1000 Pa

DSH-03: I-time high limit static pressure control

0 sec