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T408 (Dirty Air Filter)
If no dirty filter switch is installed, the switch will read "clean fil-
ter" all the time. Therefore the dirty filter routine runs continuous-
ly and diagnoses the input. Because of the different possible times
it takes to generate static pressure, this routine waits 2 minutes af-
ter the fan starts before the dirty filter switch is monitored. If the
dirty filter switch reads "dirty filter" for 2 continuous minutes, an
alert is generated. No system action is taken. This is a reminder
that it is time to change the filters in the unit. Recovery from this
alert is through a clearing of all alarms (manual) or after the dirty
filter switch reads clean for 30 continuous seconds (automatic).
T409 (Supply Fan Commanded On, Sensed Off Failure)
T409 (Supply Fan Commanded Off, Sensed On Failure)
A409 (Supply Fan Commanded On, Sensed Off Failure)
A409 (Supply Fan Commanded Off, Sensed On Failure)
Both the alert and the alarm refer to the same failure. The only dif-
ference between the alarm and alert is that in the case where the
supply fan status configuration to shut down the unit is set to YES
(Configuration
UNIT
SFS.S), the alarm will be generated
AND the unit will be shut down. It is possible to configure Con-
figuration
UNIT
SFS.M to either a switch or to monitor a 0.2
in. wg rise in duct pressure if the unit is VAV with duct pressure
control (IGV or VFD).
The timings for failure for both are the same and are illustrated in
the following table:
UNIT TYPE/MODE
MINIMUM ON TIME WAIT
CV (no gas heat)
30 seconds
CV (gas heat)
2 minutes
VAV (no gas heat)
1 minute
VAV (gas heat)
3 minutes
Recovery is manual. Reason for failure may be a broken fan belt,
failed fan relay, or failed supply fan status switch.
A410 (Supply Fan VFD Fault)
The MBB has received a fault status from the supply fan VFD.
The unit will be shut down and a manual reset is required. The
VFD keypad will indicate which fault has occurred. Reset can be
done at the unit control (Alarms
A411 (Exhaust Fan VFD Fault)
The MBB has received a fault status from the exhaust fan VFD.
Building pressure control will be stopped and a manual reset is re-
quired. The VFD keypad will indicate which fault has occurred.
Reset can be done at the unit control (Alarms
VFD keypad.
T414 (Damper Not Modulating)
This alert occurs when the supply air temperature does not
change as expected when the damper is moved. Check to deter-
mine if the damper is no longer mechanically connected to the
actuator. Reset is automatic on economizers with only one actua-
tor. Manual reset is required on economizers with two actuators.
T421 (Thermostat Y2 Input On without Y1 On)
If Y2 is on and Y1 is off, then this alert condition is initiated. The
control continues as if both Y1 and Y2 were requested. Alert re-
covery will not occur until Y1 is seen. This handles some condi-
tions of an incorrectly wired thermostat and may prevent multiple
alerts and recoveries from clogging the alarm histories.
T422 (Thermostat W2 Input On without W1 On)
If W2 is on and W1 is off, then this alert condition is initiated. The
control continues as if both W1 and W2 were requested. Alert re-
covery will not occur until W1 is seen. This handles some condi-
tions of an incorrectly wired thermostat and may prevent multiple
alerts and recoveries from clogging the alarm histories.
T423 (Thermostat Y and W Inputs On)
Simultaneous calls for heating and cooling are illegal and will be
alarmed. Cooling and heating will be locked out. Recovery is au-
tomatic when the condition no longer exists.
MINIMUM OFF TIME WAIT
1 minute
4 minutes
1 minute
4 minutes
R.CUR) or the VFD keypad.
R.CUR) or the
T424 (Thermostat G Input Off On a Cooling Call)
If G is off and there is a cooling request (Y1 or Y2), then it is pos-
sible the G connection has not been made to the unit terminal
block. An alert is initiated for this condition as continuous fan op-
eration and manual fan control may not be possible. Cooling is
started, if allowed, and the fan is turned on. The controls do not di-
agnose the fan if a heat request (W1 or W2) is in progress.
T430 (Plenum Pressure Safety Switch Trip)
A430 (Plenum Pressure Safety Switch Trip)
If the unit is configured for fan tracking and the plenum pressure
switch trips, the unit will be instructed to shut down immediate-
ly. The first 2 times the switch trips, the unit will automatically
start up and clear the alert 3 minutes after the switch recovers.
The third time the switch trips, the unit shuts down and calls out
the alarm. Manual reset of the switch (located in the auxiliary
control panel) is required. Software reset is automatic when
switch has been reset. Possible causes are blocked exhaust or re-
turn dampers causing high pressure at the plenum fan.
T431 (Power Exhaust Motor Starter Protector Trip)
A432 (Power Exhaust Motor Starter Protector Lock)
If the unit is configured for VFD power exhaust (BP.CF=3), the
unit monitors the status of the (2) Power Exhaust Motor Starter
Protectors in the power leads between the PE VFD and the PE
Motors. If either one of the Motor Starter Protectors trip, the alert,
T431, will be broadcast. The Building Pressure routine will con-
tinue to operate but with only one power exhaust fan. Depending
on the operating conditions, the unit may not be able to maintain
the desired building pressure.
If both of the Motor Starter Protectors trip, the alert, A432, will be
broadcast and the Building Pressure Control routine will shut
down. Possible causes are overloading of the Power Exhaust Mo-
tor(s) or wrong setting for the Motor Starter Protector(s). Software
reset is automatic when the switch(es) have been reset.
T500 (Current Sensor Board Failure - A1)
T501 (Current Sensor Board Failure - A2)
T502 (Current Sensor Board Failure - B1)
T503 (Current Sensor Board Failure - B2)
T504 (Current Sensor Board Failure - A3)
T505 (Current Sensor Board Failure - B3)
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
active for a minimum of 15 seconds to provide the application a
reasonable time to catch the failure. Compressors will not be in-
hibited by this failure. Recovery is automatic. Reason for failure
may be a faulty current sensor board, incorrect wiring, or a dam-
aged input on the MBB control board.
T610 (Economizer Actuator Out of Calibration)
A620 (Economizer 2 Actuator Out of Calibration)
T630 (Humidifier Actuator Out of Calibration)
A640 (Heating Coil Actuator Out of Calibration)
A650 (Bldg.Press. Actuator 1 Out of Calibration)
A660 (Bldg.Press. Actuator 2 Out of Calibration)
Each of the actuators must have a minimum control range to oper-
ate. If the actuator, after a calibration, has not learned a control
range appropriate for the application, this alarm/alert will be sent.
No action will be taken on this error. Recovery is automatic. Rea-
son for failure may be an obstruction or stuck linkage that prevents
full range calibration.
T611 (Economizer Actuator Comm Failure)
A621 (Economizer 2 Actuator Comm Failure)
T631 (Humidifier Actuator Communication Failure)
A641 (Heating Coil Actuator Comm Fail)
A651 (Bldg.Press. Actuator 1 Comm Failure)
A661 (Bldg.Press. Actuator 2 Comm Failure)
Each of the actuators communicates over the local equipment net-
work (LEN). If this error occurs, then it is impossible to control
the actuator. Depending on the function of the actuator, the control
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Table of Contents
Troubleshooting
