Maintenance; Diagnostics - Trane LPC Install And Operation Instructions

Diagnostics

Table M-D-2 describes the diagnostics that
can be generated by the Tracer AH540/
541 controller. There are three types of
diagnostics:
1. Critical: The controller shuts down the
unit to prevent possible damage. The
controller cannot operate until the
diagnostic condition is corrected.
2. Service required: The controller disables
certain sequences of operation while
attempting to maintain unit operation.
For example, if the mixed-air
temperature sensor fails or is not wired,
the controller disables economizer
operation.
3. Informational: The controller operates
normally.
Resetting diagnostics
Diagnostics that cause the unit to
shutdown or disable certain operations
are either latching or non-latching.
Latching diagnostics require manual
resetting. Non-latching diagnostics
automatically clear when the condition
that caused the diagnostic is solved.
Resetting is similar to cycling power to the
unit. Resetting clears any latching diag-
nostics and allows the controller to restart
the air-handling unit, if it is running
normally. If the condition that caused the
latching diagnostic is still present, how-
ever, the controller immediately shuts
down the unit.
You can reset diagnostics in a variety of
ways:
• Manual output test
• Cycling power to the controller
• Building automation system
• Rover service tool
• Any communicating device able to
access the diagnostic reset input of
the controller
• Zone sensor fan mode switch
• Operator display
Manual output test
Use the Test button on the controller
during installation to verify proper end-
device operation or during
troubleshooting. When you press the Test
button, the controller exercises all outputs
in a predefined sequence. The first and last
outputs of the sequence reset the
controller diagnostics. See "Performing a
manual output test" .
90

Maintenance

Cycling power
When the 24 Vac power to the controller
is turned Off and then On, the unit cycles
through a power-up sequence (see
"Power-up sequence"). By default, the
controller attempts to reset all diagnostics
during this sequence.
Building automation system
Some building automation systems can
reset controller diagnostics. For more
complete information, refer to the
product literature for the building
automation system.
Rover service tool
You can reset controller diagnostics with
the Rover service tool (see the Rover
Operation and Programming guide,
EMTX-SVX01E-EN).
Diagnostic reset input
Any device that can communicate the
network variable nviRequest
(enumeration "clear_alarm") can reset
controller diagnostics.
Zone sensor fan mode switch
When the zone sensor fan mode switch is
changed from Off to Auto, the controller
attempts to reset all diagnostics. If the
zone sensor fan mode switch has been
disabled by configuration, then the switch
is ignored and cannot be used to reset
diagnostics.
Table M-D-1. Diagnostics in order of priority
diagnostics
Operator display
You can view and reset active diagnostics
from the operator display. Active
diagnostics are indicated by a flashing
status light on the display.
Interpreting multiple diagnostics
Two or more diagnostics can be present
at the same time. Diagnostics are
reported in the order in which they occur,
but each diagnostic has a different
priority. For example, if a freezestat
condition occurs, the controller
communicates a Low Temp Detect
diagnostic message at priority one, shuts
down the air-handler, and opens all
valves. If a stop input condition
then occurs, the controller communicates
a Unit Shutdown diagnostic message at
priority two. However, because the Low
Temp Detect diagnostic has a higher
priority, the controller does not close the
valves.
Table M-D-1 lists the Tracer AH540/541
diagnostics in order of priority, with
1 being the highest and 22 being the
lowest.
Table M-D-2 interprets each diagnostic
according to what effect it has on the
controller outputs.
LPC-SVX01C-EN