Trane Tracer AH540 User Manual

Overrides
CNT-SVX05B-EN 71
freeze avoidance setpoint (configurable). The controller disables freeze
avoidance when the outdoor air temperature rises 3°F (1.67ºC) above the
freeze avoidance setpoint. When the controller is in freeze avoidance
mode:
• All water valves are driven open to allow water to flow through the
coil
• Steam and hydronic heat valves are cycled open and closed to prevent
excessive cabinet temperatures
• Supply fan is Off
• Face-and-bypass damper (when present) is at full bypass
Freeze avoidance protects the air-handling unit hydronic heating and
cooling coils from freezing when cold outdoor air temperatures are
present and the supply fan is Off. For example, the Tracer AH540/541 is
not able to run the air-handling unit because the run/stop input is set to
stop (supply fan is Off). If the outdoor air temperature is below the freeze
avoidance setpoint, the Tracer AH540/541 opens all water valves.
Overrides
The controller has the capability, whether using space temperature con-
trol or discharge air temperature control, to override both analog and
binary output (typically for testing and commissioning) through the
Tracer Summit building automation system or from the Rover service
tool. For more information about the output overrides, refer to literature
for those products.
In addition, AH540/541 override capability include:
• Manual output test
• Emergency override
• Water valve override
Manual output test
The controller includes a manual output test function, which allows the
user to manually exercise the outputs in a predefined sequence using the
Test push button (see “Performing a manual output test” on page 84). You
can also perform the manual output test remotely using the Rover service
tool. The Rover service tool communications through the Comm5 link to
place the controller in service override mode. From the Rover computer
screen you can step the controller through the manual output test.
Emergency override
The Tracer AH540/541 controller can be placed into emergency override
by using the communication variable (nviEmergOverride). Emergency
override allows a building automation system such as Trane Tracer Sum-
mit to pressurize, depressurize, or purge the air from a building space. It
can also be used to shut down the controller operation of the unit.

Trane Tracer AH540 Specifications

General

Brand	Trane
Model	Tracer AH540
Category	Controller
Language	English