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Alarms"R.HIST (Reset Alarm History)
Change to YES to reset the alarm history. Turning unit power off
will not reset the alarm history.
Alarms"CURR (Currently Active Alarms)
Use the ENTER key, then scroll through any alarm numbers using
the up and down arrow keys. Alarms are displayed in numerical
order.
Alarms"HIST (Alarm History)
Use the ENTER key, then scroll through any alarm numbers using
the up and down arrow keys. Up to 20 alarms are displayed in
order of occurrence, with time and date.
The description for an alarm can be viewed on the Scrolling
Marquee display by pressing ESCAPE and ENTER keys
simultaneously while displaying the alarm code number. Be sure to
expand description for each code, because in some cases there are
different possible descriptions and causes for the same code
number.
Diagnostic Alarm Codes and Possible Causes
Alert Codes T051, T052, T055 and T059
There are 4 different texts for each alert code. There are two
different alerts which have corresponding test mode alerts indicated
with "Service Test" in the expanded text. Pressing enter and esc on
the marquee or navigator to expand the T051, T052, T055, or
T059 alert will show you one of the below alerts. Make sure the
expanded text is read correctly before troubleshooting. Alert codes
T051, T052, T055, and T059 are for compressors A1, A2, B1, and
C1, respectively.
S Compressor Safety Trip
These alerts occur when the Current Sensor (CS) does not detect
compressor current during compressor operation. When this
occurs, the control turns off the compressor and logs a strike for
the respective circuit. These alerts reset automatically. The
possible causes are: high−pressure switch (HPS) open (The HPS
is wired in series with compressor relays on the MBB. If the
high−pressure switch opens during compressor operation, the
compressor stops, and the CS no longer detects current, causing
the control to activate this alert), compressor internal protection
is open, or a wiring error (a wiring error might not allow the
compressor to start).
To check out the alert:
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, incorrect safety wiring, or incorrect compressor
wiring.
2. If the compressor starts, verify that the indoor and outdoor
fans are operating properly.
3. 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.
4. Return to Normal mode and observe compressor operation
to verify that compressor current sensor is working and
condenser fans are energized after compressor starts.
S Compressor Current Detected After Turnoff
These alerts occur when the Current Sensor (CS) detects current
when the compressor should be off. When this occurs, the
control turns off all of the compressors. Use the Scrolling
Marquee to reset the alert. The possible causes are a welded
contactor or frozen compressor relay on MBB.
To check out alert:
1. Place the unit in Service Test mode. All compressors should
be Off.
2. Verify that there is not 24vac at the contactor coil. If there is
24vac 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 operation
to verify that compressor current sensor is working and
condenser fans are energized after compressor starts.
Alert Codes T064, T065 and T080 – Circuit Saturated
Condensing Temp Thermistor Failure
Alert codes T064, T065, and T080 are for circuits A, B and C,
respectively. These alerts occur when the temperature is outside the
range –40_ to 240_F (–40_ to 116_C). When this occurs, the
control will use only the outdoor temperature to control the
outdoor fans. If both the SCT and OAT fail, then circuit shutdown
alarm will occur also. 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 T066, T067, and T081 − Circuit Saturated Suction
Temperature Thermistor Failure
Alert codes T066, T067, and T081 are for circuits A, B and C,
respectively. These alerts occur when the unit's suction transducers
are turned off internally. Cooling will not operate. This is usually
due to a network force on a non exposed CCN point. Reload
factory defaults or reinstall software on the MBB. Consult the
network manager if alert continues.
Alert Code T073 − Outdoor Air Temperature Thermistor
Failure
This alert occurs when the temperature is outside the range –40_ to
240_F (–40_ to 116_C). For all units, all ambient temperature
lockout limits for cooling and heating are ignored. For all units, if
both SCT and OAT fail, then circuit shutdown alarm will also
occur. For economizer equipped units, the economizer will not
operate to provide cooling. The economizer will still operate for
ventilation. The control will use condenser temperatures for
outdoor fan control. For units with CCH crankcase heat relay
control, the crankcase heat relay will be turned on if any
compressor is off. 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 T074 − Space Temperature Thermistor Failure
This alert occurs when the temperature is outside the range –40_ to
240_F (–40_ to 116_C). This alert will only occur if the unit
control type is configured for Space Sensor (versus Thermostat).
Cooling and heating will not operate. For economizer equipped
units, the economizer will still operate for ventilation. This alert
resets automatically. The cause of the alert is usually a faulty
thermistor in the T−55, T−56, or T−58 device, a shorted or open
thermistor caused by a wiring error, or a loose connection.
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Table of Contents
Troubleshooting
