98
• Compressor internal overload protector is open. Internal
overload protectors are used in the Copeland compressors in
all units except size 60 ton units with voltages of 208/230-v,
380-v, and 575-v.
• Compressor external overload protector (Kriwan module)
has activated. The Copeland compressors in size 60 ton
units with voltages of 208/230-v, 380-v, and 575-v use
external overload protector modules that are mounted in the
compressor wiring junction box. Temperature sensors
embedded in the compressor motor windings are the inputs
to the module. The module is powered with 120 vac from
the units main control box. The module output is a normally
closed contact that is wired in series with the compressor
contactor coil. In a compressor motor overload condition,
the contact opens de-energizing the compressor contactor.
• Circuit breaker trip. The compressors are protected from
short circuit by a breaker in the control box. On the 020-050
size units there is one breaker per two compressors and on
the 060 size units there is one breaker per compressor.
• Wiring Error. A wiring error might not allow the compres-
sor to start.
To check out alerts 051, 052, 055 and 056:
1. Turn on the compressor in question using Service Test
mode. If the compressor does not start, then most likely
the problem is one of the following: HPS open, open
internal protection, circuit breaker trip, incorrect safety
wiring, or incorrect compressor wiring.
2. If the compressor does start verify it is rotating in the
correct direction.
A051 (Circuit A, Compressor 1 Stuck On Failure)
A052 (Circuit A, Compressor 2 Stuck On Failure)
A055 (Circuit B, Compressor 1 Stuck On Failure)
A056 (Circuit B, Compressor 2 Stuck On Failure) — Alarm
codes 051, 052, 055, and 056 are for compressors A1, A2, B1,
B2 respectively. These alarms occur when the current sensor
(CS) detects current when the compressor should be off. When
this occurs, the control turns off the compressor and logs a strike
for the respective circuit. Use the scrolling marquee to reset the
alarm.
If the current sensor board reads ON while the compressor
relay has been commanded OFF for a period of 4 continuous
seconds, an alarm is generated. These alarms are only moni-
tored for a period of 10 seconds after the compressor relay has
been commanded OFF. This is done to facilitate a service tech-
nician forcing a relay to test a compressor.
In addition, if a compressor stuck failure occurs and the cur-
rent sensor board reports the compressor and the request off,
certain diagnostics will take place.
1. If any of the 4 compressors are diagnosed as stuck on and
the current sensor board is on and the request is off, the
control will request the supply fan which will automati-
cally start building airflow control. Condenser fans will
also be commanded on to maintain normal head pressure.
2. Heating will be disabled while any one of the compres-
sors has this problem.
The possible causes are:
• welded contactor
• frozen compressor relay on MBB
To check out alarms 051, 052, 055, and 056:
1. Place the unit in Service Test mode. All compressors
should be off.
2. Verify that there is not 24 v at the contactor coil. If there is
24 v at the contactor, check relay on MBB and wiring.
3. Check for welded contactor.
4. Verify CS wiring.
5. Return to Normal mode and observe compressor opera-
tion to verify that compressor current sensor is working
and condenser fans are energized after compressor starts.
T072 (Evaporator Discharge Reset Sensor Failure)
— If the
unit is configured to use the remote EDT 4 to 20 mA reset in-
put (
Configuration
EDT.R
RES.S
) and the sensor reading
is less than 2 mA then the alert will occur. When this occurs the
control will default to the internal setpoints. The sensor is
connected to the optional CEM module. For this sensor to be
used, the EDT 4 to 20 mA reset input (
Configuration
EDT.R
RES.S
) must be set to “enabled.”
T073 (Outside Air Temperature Thermistor Failure) — This
alert occurs when the outside air temperature sensor (
Temper-
atures
AIR.T
OAT
) is outside the range –40 to 240 F
(–40 to 116 C). Failure of this thermistor (
Tempera-
tures
AIR.T
OAT
) will disable any elements of the control
which requires its use. Economizer control beyond the vent
position and the calculation of mixed-air temperature for the
sumZ algorithm will not be possible. This alert resets automati-
cally. The cause of the alert is usually a faulty thermistor, a
shorted or open thermistor caused by a wiring error, or a loose
connection.
T074 (Space Temperature Thermistor Failure) — This alert
occurs when the space temperature sensor (
Temperatures
AIR.T
SPT
) is outside the range –40 to 240 F (–40 to
116 C). This alert will only occur if the unit is configured to use
a space temperature sensor. Configuration is done through
the Unit Control Type (
Configuration
UNIT
C.TYP
)
configuration. Failure of this thermistor (
Tempera-
tures
AIR.T
SPT
) will disable any elements of the control
which requires its use. If the unit is configured for SPT 2 stage
or SPT multi-stage operation and the sensor fails, no cooling or
heating mode may be chosen. This alert resets automatically.
The cause of the alert is usually a faulty thermistor in the T55,
T56, or T58 device, a shorted or open thermistor caused by a
wiring error, or a loose connection.
T075 (Return Air Thermistor Failure) — This alert occurs
when the return air temperature sensor (
Tempera-
tures
AIR.T
RAT
) is outside the range –40 to 240 F (–40 to
116 C). The RAT is standard on all units and is located in the
return section near the auxiliary control box. This alert resets
automatically. The cause of the alert is usually a faulty thermis-
tor, a shorted or open thermistor caused by a wiring error, or a
loose connection.
Failure of this thermistor (
Temperatures
AIR.T
RAT
)
will disable any elements of the control which requires its use.
Elements of failure include:
• the calculation of mixed air temperature for sumZ control
• the selection of a mode for VAV units
• economizer differential enthalpy or dry bulb control
• return air temperature supply air reset
IMPORTANT: Prolonged operation in the wrong direction
can damage the compressor. Correct rotation can be veri-
fied by a gage set and looking for a differential pressure
rise on start-up.
IMPORTANT: If the compressor starts, verify that the
indoor and outdoor fans are operating properly.
IMPORTANT: If the CS is always detecting current, then
verify that the compressor is on. If the compressor is on,
check the contactor and the relay on the MBB. If the com-
pressor is off and there is no current, verify CS wiring and
replace if necessary.
IMPORTANT: Return to Normal mode and observe com-
pressor operation to verify that compressor current sensor
is working and condenser fans are energized after compres-
sor starts.
Summary of Contents for Carrier Weathermaker 48A2
Page 105: ...105 Fig 20 Typical Main Control Box Wiring Schematic 48 50A2 A3 A4 A5 Units...
Page 106: ...106 Fig 21 Typical Auxiliary Control Box Wiring Schematic...
Page 107: ...107 Fig 22 Typical 2 Stage Gas Heat Wiring Schematic Size 060 Units Shown a48 8357...
Page 108: ...108 TO NEXT PAGE Fig 23 Typical Staged Gas Heat Wiring Schematic Size 060 Units Shown A48 7296...
Page 109: ...109 Fig 23 Typical Staged Gas Heat Wiring Schematic Size 060 Units Shown cont A48 8358...
Page 110: ...110 Fig 24 Typical Electric Heat Control Schematic 50 Series Size 060 Units Shown a50 8228...
Page 111: ...111 Fig 25 Typical Power Schematic 48 50A2 A3 A4 A5 060 Unit Shown...
Page 112: ...112 Fig 26 Typical Low Ambient Controls Option Wiring...
Page 113: ...113 Fig 27 Typical Small Chassis Component Location Size 020 035 Units...
Page 114: ...114 Fig 28 Typical Large Chassis Component Locations Size 040 060 Units...
Page 118: ...118 Fig 30 Economizer Control Board ECB1 and VAV Control Board ECB2 A48 7706...
Page 142: ...142 A48 3733 Fig 56 Main Burner Removal...
Page 176: ...176 APPENDIX C VFD INFORMATION cont Fig F Internal Enclosure Fan Replacement A48 7716...
