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TROUBLESHOOTING
By using the display module, actual operating conditions
of the unit are displayed while it is running. The Quick Test
function allows proper operation of compressors, compres-
sor unloaders, fans, and other components to be checked while
unit is stopped. If an operating fault is detected, an alarm is
generated and an alarm code(s) is displayed. For checking
specific items, see Table 20.
Checking Display Codes — To view the digital dis-
play codes, press the button located to the right of the LED
display/set point board in the control box. See Table 21 for
Operational Status Codes. SeeTable 22 for Diagnostic Codes.
Complete Unit Stoppage — If the unit is off, there
are several conditions that can cause this situation to occur:
• Remote ON/OFF circuit in Unoccupied mode.
• Unit ON/OFF switch moved to OFF position.
• Programmed schedule at the timeclock.
• General power failure.
• Blown fuse in the control power feed.
• Open control circuit fuse.
• Operation of the unit blocked by the demand limit
function.
• Unit supply-air temperature (T1) thermistor failure.
• Supply-air fan is not operating.
• High duct static pressure.
Single Circuit Stoppage — If a single circuit stops,
there are several potential causes:
• Open contacts in the compressor high-pressure switch.
• Low refrigerant pressure.
• Thermistor failure.
• Unit supply-air temperature thermistor (T1) failure.
• Compressor circuit breaker trip.
• Operation of the circuit blocked by the demand limit
function.
Table 21 — Operation Status Codes
CODE MEANING
□
0
0 cooling stages active
□
1
1 cooling stage active
□
2
2 cooling stages active
□
3
3 cooling stages active
□
4
4 cooling stages active
□
5
5 cooling stages active
□
6
6 cooling stages active
□
7
7 cooling stages active
□
8
8 cooling stages active
□
20
Initialization mode (Allow 2 minutes
for initialization. To initiate Quick Test,
press the Display button while 20 is displayed.)
□
21
Temperature Reset in effect
□
22
Demand Limit in effect
□
26
Morning Warm-Up in effect
□
30
Internal failure detected
□
88
Self-diagnostic mode in effect
Restart Procedure — Before attempting to restart the
machine, check the display for alarm codes to determine the
cause of the shutdown. If the unit, circuit, or compressor stops
more than once as a result of a safety device, determine and
correct the cause before attempting to start the unit again.
After the cause of the shutdown has been corrected, unit
restart may be automatic or manual depending upon the fault.
Table 20 — Controls Troubleshooting
SYMPTOM(S) PROBABLE CAUSE(S) SOLUTION(S)
Controls do not seem
to be operating.
Remote on-off function may be
keeping controls off.
Check status.
Evaporator fan does not run. 1. Circuit breaker open.
2. Inverter overload (if equipped).
1. Find cause and reset circuit breaker.
2. Find cause and reset.
Compressor does not run. 1. Circuit breaker is open.
2. There is no demand for cooling.
3. The control is locking out cooling operation.
4. Demand Limit in effect.
1. Find cause and reset circuit breaker.
2. Correct operation.
3. Check rotating display for alarm codes. Resolve
alarm cause and reset control by changing to
standby and back to run mode.
4. Check Demand Limit Settings.
Condenser fans do not
turn on.
Circuit breaker is open. Find cause and reset circuit breaker
Cooling demand exists and
economizer modulates, but
compression is not operating.
Compression cannot be initiated
until economizer damper is 90% open.
Correct operation.
44