73
and compressor, an alarm for that compressor will be indicated.
This will only affect that circuit; the other circuit will continue
to operate. The microprocessor is also programmed to indicate
a compressor failure if the CLO (cooling lockout) circuit to the
DSIO1, terminal J3, receives a voltage when a compressor is
not supposed to be operating. Other possible causes include a
failed contactor or DSIO module.
Alarm Code 59 (Supply-Air Thermistor Failure) — If the
temperature measured by this thermistor is outside the range of
–40 to 245 F (–40 to 118 C), heating, cooling, and economizer
use are disabled. Reset of this alarm is automatic once the prob-
lem is corrected. Start-up follows the normal sequence. The
cause of the alarm is usually a bad thermistor, a shorted or open
thermistor caused by a wiring error, or a loose connection.
Table 58 — Alarm Codes
DISPLAY
DESCRIPTION
ACTION TAKEN BY
CONTROL
RESET
METHOD
PROBABLE CAUSE
51
Compressor A1 Failure
Compressor A1 shut down
Manual
High-pressure switch open.
Wiring error.
52
Compressor A2 Failure
Compressor A2 Shutdown
Manual
High-pressure switch open.
Wiring error.
Failed contactor.
Failed DSIO module.
Circuit breaker tripped.
53
Compressor A1 Status Failure
Compressor A1 shut down
Manual
Voltage on DSIO1 J3 when compressor off.
Failed contactor.
Failed DSIO module.
Circuit breaker tripped.
54
Not used
—
—
—
55
Compressor B1 Failure
Compressor B1 shut down
Manual
High-pressure switch open.
Wiring error.
56
Compressor B2 Failure
Compressor B2 shut down
Manual
High pressure switch open.
Wiring error.
Failed contactor.
Failed DSIO module.
Circuit breaker tripped.
57
Compressor B1 Status Failure
Compressor B1 shut down
Manual
Voltage on DSIO1 J3 when compressor off.
Failed contactor.
Failed DSIO module.
Circuit breaker tripped.
58
Not Used
—
—
—
59
Supply-Air Thermistor Failure
Heating, cooling, and economizer
disabled
Automatic
Bad, shorted, or open thermistor caused by a wiring
error or loose connection.
60
Return-Air Thermistor Failure
Heating and economizer disabled
Automatic
Bad, shorted, or open thermistor caused by a wiring
error or loose connection.
61
Outdoor-Air Thermistor Failure
NTFC disabled and economizer
uses enthalpy input only. If unit has
humidity sensors, economizer
dampers close.
Automatic
Bad thermistor, wiring error, or loose connection.
62
Saturated Condensing Ther-
mistor Failure, Circuit A
Circuit A shut down
Automatic
Bad thermistor, wiring error, or loose connection. This
alarm is only valid when unit does not have pressure
transducers.
63
Saturated Condensing Ther-
mistor Failure, Circuit B
Circuit B shut down
Automatic
Bad thermistor, wiring error, or loose connection. This
alarm is only valid when unit does not have pressure
transducers.
64
Suction Thermistor
Failure, Circuit A
Superheat alarms disabled. Unit
will operate as if there are no
suction sensors.
Automatic
Bad thermistor, wiring error, or loose connection. This
alarm is only valid when unit is configured for suction
sensors.
65
Suction Thermistor
Failure, Circuit B
Superheat alarms disabled. Unit
will operate as if there are no
suction sensors.
Automatic
Bad thermistor, wiring error, or loose connection. This
alarm is only valid when unit is configured for suction
sensors.
66
Space Thermistor Failure
Temperature reset, NTFC, cooling
and heating functions disabled (CV
applications only).
Automatic
Bad thermistor, wiring error, or loose connection.
67
Compressor A1 Discharge
Pressure Transducer Failure
Circuit A shuts down
Automatic
Bad transducer, bad 5-v power supply, or a wiring error.
68
Compressor B1 Discharge
Pressure Transducer Failure
Circuit B shuts down
Automatic
Bad transducer, bad 5-v power supply, or a wiring error.
69
Compressor A1 Suction Pres-
sure Transducer Failure
Circuit A shuts down
Automatic
Bad transducer, bad 5-v power supply, or a wiring error.
70
Compressor B1 Suction Pres-
sure Transducer Failure
Circuit B shuts down
Automatic
Bad transducer, bad 5-v power supply, or a wiring error.
71
Loss of Communications with
DSIO1
All DSIO1 outputs turned off
Automatic
Faulty or improperly connected plug, faulty DSIO1
module, or wiring error.
72
Loss of Communications with
DSIO2
All DSIO2 outputs turned off
Automatic
Faulty or improperly connected plug, faulty DSIO2
module, or wiring error.
73
Loss of Communications with
PSIO2
All PSIO2 outputs turned off
Automatic
Faulty or improperly connected plug, faulty PSIO2
module, or wiring error.
74
Low Pressure, Circuit A
Circuit A compressor(s) shut down
Automatic or
Manual
Low refrigerant charge, dirty filters, evaporator fan turn-
ing backwards, inlet guide vanes not opening properly,
plugged filter drier, or faulty transducer.
75
Low Pressure, Circuit B
Circuit B compressor(s) shut down
Automatic or
Manual
Low refrigerant charge, dirty filters, evaporator fan turn-
ing backwards, inlet guide vanes not opening properly,
plugged filter drier, or faulty transducer.
76
High Pressure, Circuit A
Circuit A compressor(s) shut down
Manual
An overcharged system, high outdoor ambient tempera-
ture coupled with a dirty outdoor coil, plugged filter drier,
partially closed liquid line service valve, or a faulty trans-
ducer. This alarm is only valid when the unit has refriger-
ant pressure transducers.
