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Single Circuit Stoppage —
there are several potential causes:
1. Open contacts in the compressor high-pressure switch.
2. Low refrigerant pressure.
3. Thermistor failure
4. Transducer failure.
5. High suction superheat.
6. Low suction superheat.
7. Unit supply-air temperature thermistor (SAT) failure.
8. Compressor circuit breaker trip.
9. Operation of the circuit blocked by the demand limit
function.
10. Loss of communications between the processor mod-
ule and DSIO1 module.
Restart Procedure —
machine, check the alarms and alerts subfunctions 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.
A manual restart requires a recycle of STANDBY/RUN modes
from the HSIO or cycling OFF/ON of the control power
via control switch in the unit control box. To recycle the
STANDBY/RUN modes, enter the
Scroll down to STBY function. Press
STANDBY, then press
CLEAR ENTER
RUN). Manual reset conditions may also be cleared through
the ComfortWORKS® or Service Tool software by selecting
Modify, Controller, Configuration and downloading "Unit Re-
set YES" from the configuration screen. All of the fault condi-
tions are described in the Diagnostics Alarm Codes and Possi-
ble Causes section.
Alarms and Alerts —
abnormal or fault conditions, and may cause either one circuit
or the whole unit to shut down. They are assigned code num-
bers as described below. The alarm descriptions are displayed
on the HSIO when the
communication loss occurs to a hardware point, an alert or
alarm may be generated. Refer to Table 14 for Alert Limits.
The PSIO also recognizes illegal configurations.
Table 58 contains a detailed description of each alarm and
alert code error and possible cause.
To determine how a unit is operating, check the diagnostic
information available (
operating mode displays (
Control Modules section on page 81. If the display is working:
1. Note all alarm codes displayed under
2. Note all operating mode codes displayed under
.
3. Note the modified supply-air set point in effect and the
current supply-air temperature under
.
a. If reset is in effect, the modified set point may be
different from the supply-air set point because the
space temperature is below the reset set point.
b. If demand limit is in effect, the unit may be incapa-
ble of producing the desired supply-air set point
due to the decreased capacity of the unit.
If a single circuit stops,
Before attempting to restart the
subfunction.
to enter
ENTER
to exit STANDBY (re-enter
Alarms and alerts are warnings of
subfunction is entered. When a
through
) and the
). If no display appears, see
.
c. Check the programming of the schedule function to
see if occupied or unoccupied set point should be in
effect.
NOTE: To disable unit operation, press
unit in Standby mode.
DIAGNOSTIC
CAUSES (See Table 58):
Alarm Codes 51 and 55 (Compressor Fault)\ — Alarm code
51 is for a fault on compressor A1, and alarm code 55 is for a
fault on compressor B1. If the DSIO1 relay module fails or a
compressor safety circuit switch opens during the operation of
the compressor, the microprocessor detects this fault, stops the
compressor, signals the alarm, and deenergizes the DSIO1 re-
lay to lock the compressor off. To reset the alarm, use the man-
ual method. The possible causes are:
1. High-pressure switch open (code 51 or 55, then code
76 and/or 77 if pressure transducers are installed). The
high-pressure switch is wired in series with the 24-v
supply that energizes the load side of the DSIO1 mod-
ule. If the high-pressure switch opens during compres-
sor operation, the compressor stops, and the stop is
detected by the DSIO1, terminal strip J3.
2. Wiring error. A wiring error in the control safety cir-
cuit will cause the modules to malfunction, and an
error will be indicated.
To check out alarm codes 51 or 55:
1. Scroll through the subfunction
compressor number using the
2. Energize the step (press
not start, the cause is most likely related to one of the
following: HPS (high-pressure switch) open, tripped
compressor circuit breaker or incorrect wiring in either
the safety circuit or compressor contactor coil circuit.
To follow the circuit alarm, see the unit wiring
diagram.
If the compressor starts, verify that all stages of condenser
fans are operational.
For sizes 034-078, use
tion of outputs MM, FR2, and FR3.
For sizes 088 and 104, use
eration of outputs MMA, OFA, MMB, and OFB.
Return unit to run mode and observe compressor operation
to verify that compressor lock-out circuit is working and con-
denser fans are energized after compressor starts.
NOTE: With head pressure control option enabled (
MMAS = YES), a short delay will occur before the first stage
of condenser fan(s) is energized. Check location of SCT on
condenser coil or pressure transducer wiring and pressure (if
equipped) if condenser fans do not start.
Alarm Codes 52 and 56 (Compressor Fault) — Alarm code
52 is for compressor A2. Alarm code 56 is for compressor B2.
Alarm codes 52 and 56 are a combination of the separate com-
pressor fault and compressor status codes used for compressors
A1 and B1. If the DSIO module fails, a compressor safety cir-
cuit switch opens, a circuit breaker trips, or the compressor
and
contactor fails to energize, the microprocessor detects the fault.
Alarm Codes 53 and 57 (Compressor Status) — If the com-
manded state of the compressor does not match compressor
status for 3 seconds, the corresponding compressor stops and
the proper alarm trips. This alarm will detect circuit breaker
failures, and failure of the compressor contactor to be ener-
gized. If a compressor circuit breaker trips due to compressor
overcurrent or a short or ground between the circuit breaker
72
ALARM
CODES
AND
key.
). If the compressor does
ENTER
and
to confirm opera-
ENTER
and
ENTER
and put the
POSSIBLE
to the proper
to confirm op-
,
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Table of Contents
Troubleshooting
