Specifications

81
• Internal compressor temperature sensor trip. The large
Maneurop compressors (blue) used on the 040 B1, B2, 050,
and 060 units have an internal temperature sensor.
• Circuit Breaker trip. The compressors are protected from
short circuit by a breaker in the control box. On the 020-035
and 040 A1, A2 units there is one breaker per two compres-
sors and on the 040 B1, B2 and 050, 060 compressors there
is one breaker per compressor because there is not internal
overloads.
• Wiring error. A wiring error might not allow the compressor
to start.
To check out alerts 51, 52, 55 and 56:
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 cor-
rect direction.
3. If the compressor starts, verify that the indoor and
outdoor fans are operating properly.
4. 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 compressor is
off and there is no current, verify CS wiring and replace if
necessary.
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.
Alarm Codes 51, 52, 55 and 56 (Current Detected After Turnoff)
— Alarm codes 51, 52, 55, and 56 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 alert.
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 air flow control.
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 51, 52, 55, and 56
1. Place the unit in Service Test mode. All compressors
should be Off.
2. Verify that there is not 24v at the contactor coil. If there is
24v 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.
Alert Codes 64, and 65 (Condensing Temp. Failure)
—Alert
codes 64, and 65 are for circuits A and B, respectively. These
alerts occur when the saturated condensing temperatures
(Temperatures
→ REF.T → SCT.A and SCT.B) are outside the
range –40 to 240 F (–40 to 116 C). When this occurs, the
control uses the outdoor temperature (OAT) to control the
outdoor fans. The control will default to control based on the
OAT sensor and will turn on OFC.B when the ambient is above
65 F and off when the ambient is below 50 F.
If the SCT and OAT sensors have all failed then the control
should turn on OFC.B when compressors are on.
The cause of the alert is usually a faulty thermistor, a shorted
or open thermistor caused by a wiring error, or a loose connection.
Alert Code 72 (Remote Setpoint/Rest Input Failure)
— If
theunitisconfiguredtousetheremoteEDT4to20mAreset
input (Configuration → EDT.R → RES.S) and the sensor read-
ing is less than 2 mA or greater than 22 mA then the alert will
occur. When this occurs the control will default to the internal
set points. The sensor is connected to the optional CEM module.
Forthissensortobeused,theEDT4to20mAresetinput
(Configuration
→ EDT.R → RES.S) must be set to enable.
Alert Code 73 (Outside Air Temp. Failure)
— This alert oc-
curs when the outside air temperature sensor (Te mp era-
tures → AIR.T → OAT) is outside the range –40 to 240 F (–40 to
116 C). Failure of this thermistor (Temp er atu re s
→ AIR.T
→ OAT) will disable any elements of the control which re-
quires its use. Economizer control beyond the vent position and
the calculation of mixed air temperature for the sumZ algo-
rithm will not be possible. This alert resets automatically. The
cause of the alert is usually a faulty thermistor, a shorted or
open thermistor caused by a wiring error, or a loose connection.
Alert Code 74 (Space Temp. Failure)
— This alert occurs
when the space temperature sensor (Tem per atu re s → 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 (Temperatures → 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.
Alert Code 75 (Return Air Temp. Failure)
— This alert oc-
curs when the return air temperature sensor (Te mpe ra -
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 ther-
mistor, a shorted or open thermistor caused by a wiring error, or
a loose connection.
Failure of this thermistor (Te mp eratur es
→ 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 temp supply air reset
Alert Code 76 (Outside Air Relative Humidity Sensor Fail-
ure) — This alert occurs when the outside air humidity sensor
(Inputs → REL.H → OA.RH) has a reading less than 2 mA or
greater than 22 mA. Failure of this sensor will disable any
elements of the control which requires its use including econo-
mizer outdoor and differential enthalpy control. The OA.RH
IMPORTANT: Prolonged operation in the wrong direc-
tion can damage the compressor. Correct rotation can be
verified by a gage set and looking for a differential pres-
sure rise on start-up.