Unit Protection Strategies; Filter Status; Freeze Avoidance - Trane Tracer AH540 Setup And Operation

Chapter 4 Sequence of operation
70

Unit protection strategies

The following strategies are initiated, for both space temperature control
and discharge air temperature control, when specific conditions exists in
order to protect the unit or building from damage:
Run/stop binary input (see "IN8: Run/stop" on page 25)
•
Supply fan status ("IN10: Supply fan status" on page 26)
•
Condensing unit protection
•
Coil defrost (see "Defrost operation" on page 65)
—
Compressor minimum On/Off timers (see "DX cooling operation"
—
on page 64)
Duct static pressure high limit (see "Variable-air-volume supply fan
•
operation: Duct static pressure" on page 51)
Coil freeze protection
•
Face-and-bypass heating ("Face-and-bypass damper operation" on
—
page 55)
Freeze avoidance (see "Freeze-avoidance valve cycling" on
—
page 52)
Mixed-air temperature control (see "Mixed-air temperature con-
—
trol" on page 57)
Low-temperature detection (see "IN7: Low-temperature detection
—
or coil defrost" on page 24)
Supply fan motor thermal protection (see "Electric heat operation" on
•
page 60)
Filter status (see "Filter status" on page 70)
•
Freeze avoidance (see "Freeze avoidance" on page 70)
•

Filter status

The controller filter status is based on the supply fan cumulative run
hours. The controller compares the fan run time against an adjustable fan
run hours limit (maintenance required setpoint time, stored in the con-
troller) and recommends unit maintenance as required. The Maintenance
Required diagnostic is informational only. Its state does not affect unit
operation.
Use the Rover service tool to edit the Maintenance Required setpoint
time. When the setpoint limit is exceeded, the controller generates a
Maintenance Required diagnostic. To disable the diagnostic feature, set
the maintenance required setpoint time to zero.
You can use Rover service tool or Tracer Summit to clear the Maintenance
Required diagnostic. When the diagnostic is cleared, the controller resets
the fan run time to zero and resumes accumulating fan run hours.

Freeze avoidance

Freeze avoidance is used as low ambient temperature protection and is
only initiated anytime the supply fan is Off. The controller enters the
freeze avoidance mode when the outdoor air temperature is below the
CNT-SVX05B-EN