Variable-Air-Volume Supply Fan Operation: Duct Static Pressure - Trane Tracer AH540 Setup And Operation

Supply fan operation
ing or cooling requirements. The supply fan is normally Off during unoc-
cupied modes of operation when space temperature is between the
unoccupied heating and cooling setpoints.
If the controller is wired to a Trane zone sensor, the user can change the
supply fan operation through the fan mode switch (when present). When
the fan mode switch is in the Off position, the controller shuts down the
unit. If the fan mode switch is moved to the Auto position, the controller
operates the fan On and Off according to heat and cool demands and the
active occupancy mode.
Variable-air-volume supply fan operation: Duct static
pressure
For variable-air-volume supply fan operation, the controller must be con-
figured for both discharge air temperature control and for variable-air-
volume fan operation.
When configured for variable-air-volume operation, the controller uses a
duct static pressure control routine. Variable-air-volume operation always
maintains duct static pressure control in all modes of operating with the
supply fan On. The air-handling unit duct static pressure is maintained
by a duct static pressure control sequence.
The supply fan variable frequency drive in a variable-air-volume system
is controlled to maintain the duct static pressure setpoint. When the fan
is On, the controller reads and compares the duct static pressure input to
the duct static pressure setpoint and adjusts the supply fan speed analog
output signal (AO1) to the variable frequency drive.
The duct static pressure signal can be from a wired sensor or communi-
cated via a network variable. If the controller does not have a valid duct
static pressure from a wired sensor or communicated, the controller gen-
erates a Duct Static Press Failure diagnostic and shuts down the unit.
The controller does not operate duct static pressure control without a
valid duct static pressure input.
If the controller has both a hard-wired and communicated duct static
pressure input, the communicated value is used for duct static pressure
control. The greater of the two values, local (hard-wired) or communi-
cated, is used for duct static pressure high limit shutdown.
The Tracer AH540/541 controller has a configurable duct static pressure
high limit setpoint. If the duct static pressure exceeds the duct static
pressure high limit setpoint, the controller shuts down the unit and gen-
erates a Duct Static Press High Limit diagnostic. This latching diagnostic
must be cleared from the controller before the unit is allowed to operate.
CNT-SVX05B-EN 51