110
T414 (Damper Not Modulating)
This alert occurs when the damper not modulating. The alert oc-
curs when SAT does not change as expected when the damper is
moved. It is typically an indication that the damper has become
mechanically disconnected from the actuator. Investigate the ac-
tuator and damper, and fix it. This alert resets automatically.
T420 (R-W1 Jumper Must be Installed to Run Heat in Ser-
vice Test)
This alert occurs when a request for a heat output has occurred
yet the W1 input is not high. A jumper must be installed be-
tween R and W1 when trying to test heat in Service Test. The
alert will clear when Service Test is exited or if another Service
Test mode is selected. Remove jumper when done using Ser-
vice Test if the unit is operating with a thermostat. The jumper
should only be left in place if the unit is operating with a space
temperature sensor.
T421 (Thermostat Y2 Input On without Y1 On)
This alert occurs in Thermostat Mode when Y2 is energized
and Y1 is not. Verify thermostat and thermostat wiring. When
Y2 turns on, the software will behave as if Y1 and Y2 are both
on. When Y2 turns off, the software will behave as if Y1 and
Y2 are both Off. This alert resets automatically when Y1 is
turned on.
T422 (Thermostat W2 Input On without W1 On)
This alert occurs in Thermostat Mode when W2 is energized
and W1 is not. Verify thermostat and thermostat wiring. When
W2 turns on, the software will behave as if W1 and W2 are
both on. When W2 turns off, the software will behave as if W1
and W2 are both off. This alert resets automatically when W1
is turned on.
T423 (Thermostat Y and W Inputs On)
This alert occurs in Thermostat Mode when Y1 or Y2 is ener-
gized simultaneously with W1 or W2. Verify thermostat and
thermostat wiring. The software will enter either the cooling or
heating mode depending upon which input turned on first. This
alert resets automatically when Y1 and Y2 are not on simulta-
neously with W1 and W2.
T424 (Thermostat G Input Off On a Cooling Call)
This alert occurs in Thermostat Mode when the fan is not re-
quested (G = ON) during cooling (Y1 or Y2 = ON). Verify
thermostat and thermostat wiring.
T500 (Current Sensor Board Failure – A1)
T501 (Current Sensor Board Failure – A2)
T502 (Current Sensor Board Failure – B1)
T503 (Current Sensor Board Failure – B2)
Alert codes 500, 501, 502, and 503 are for compressors A1,
A2, B1, and B2 respectively. These alerts occur when the out-
put of the current sensor (CS) is a constant high value. These
alerts reset automatically. If the problem cannot be resolved
and the CS board must be replaced, the CS board can be tem-
porarily disabled while securing a replaced board. A CS board
is disabled by setting Configuration
COOL
CS.A1,
CS.A2, CS.B1 or CS.B2 to Disable.
If the current sensor board malfunctions or is not properly con-
nected to its assigned digital input, an alert will be generated. It
takes 2 to 4 seconds to log the alert. If the alert is logged, it
stays for a minimum of 15 seconds to provide the application a
reasonable time to catch the failure. Compressors will be not
be inhibited by this failure. Recovery is automatic. Reason for
failure may be a faulty current sensor board, incorrect wiring,
or a damaged input on the MBB control board.
A700 (Supply Air Temperature Sensor Failure)
This alarm indicates a failure of the sensor supply air temperature
sensor or the leaving air temperature sensor (if using hydronic
heat). This alarm occurs when the temperature sensor (Tempera-
tures
AIR.T
SAT) is outside the range –40 to 240°F (–40 to
116°C). This alarm resets automatically. The cause of the alarm is
usually a faulty thermistor, a shorted or open thermistor caused by
a wiring error, or a loose connection.
T701 (Staged Gas 1 Thermistor Failure)
T702 (Staged Gas 2 Thermistor Failure)
T703 (Staged Gas 3 Thermistor Failure)
If any of the staged gas thermistors (Temperatures
AIR.T
S.G.L1-3) fails, an alert will be generated and the remaining
thermistors will be averaged together (Temperatures
AIR.T
S.G.LS) without the failed thermistor. Recovery is automat-
ic. Reason for failure may be incorrect wiring, faulty thermis-
tor, or a damaged input on the staged gas control board (SCB).
A704 (Staged Gas Leaving Air Temperature Sum Total Failure)
If all three staged gas thermistors (Temperatures
AIR.T
S.G.L1-3) fail (the sensor is outside the range of –40°F to 240°F),
staged gas will be shut down and this alarm will be generated. Re-
covery is automatic. Reason for failure may be faulty wiring,
faulty thermistors, or damaged inputs on the staged gas control
board (SCB).
T705 (Limit Switch Thermistor Failure)
A failure (the sensor is outside the range of –40°F to 240°F) of
this thermistor (Temperatures
AIR.T
S.G.LM) will cause
an alert to occur and a disabling of the limit switch monitoring
function for the staged gas control board (SCB). Recovery is
automatic. Reason for failure may be due to faulty wiring, a
faulty thermistor, or a damaged input on the staged gas control
board (SCB).
A706 (Hydronic Evap Discharge Thermistor Failure)
If the unit is configured for Humidi-MiZer, then the unit has a
thermistor (Temperatures
AIR.T
CCT) installed between
the evaporator coil and the Humidi-MiZer coils that functions as
the evaporator discharge temperature thermistor for cooling. If
this thermistor fails, an alarm will be generated and the system
will be shut down. Recovery is automatic. Reason for failure
may be due to faulty wiring, a faulty thermistor, or a damaged
input on the EXV control board.
T707 (Digital Scroll Discharge Thermistor Failure)
If the RXB control board is not receiving a signal from the dis-
charge temperature thermistor, the alarm is generated. The
thermistor may be missing, disconnected, or a wire may be
broken. The alert will be generated and the digital scroll capac-
ity will be locked at 50%. Reset is automatic.
T800 (Cannot Enable MLV and Digital Scroll Simultaneously)
MLV and Digital Scroll compressor cannot function together.
When both options are enabled, an alert will occur.
T802 (R22 Invalid for Design Series 4)
For a unit with Design Series 4 model number, R-22 cannot be
chosen as refrigerant type. When R-22 is configured in the re-
frigerant type, an alert will occur warning the user to choose
R-410A as refrigerant.
MAJOR SYSTEM COMPONENTS
General
The 48/50A Series package rooftop units with electric cooling
and with gas heating (48A units) or electric cooling and elec-
tric heating (50A units) contain the ComfortLink electronic
control system that monitors all operations of the rooftop. The
control system is composed of several components as listed be-
low. See Fig. 20-27 for typical control and power component
schematics. Figures 28 and 29 show the layout of the control
box, unit, and thermistor and transducer locations.
To Next Page
Loading...
