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Troubleshooting System 450 Control Systems
System 450 control modules display error messages when the module detects a
sensor, sensor wiring, sensor power, or power supply failure.
Table 9 shows the System 450 error messages that may be displayed, and provides
possible causes for the error messages and the solutions for remedying the errors.
Table 9: System 450 Control System Error Messages
Error Screen
Problem/Symptom
Sensor failure is
detected and < SNF > is
displayed (instead of a
value).
Outputs that reference
the failed sensor are
operating in the Sensor
Failure Modes selected
for the Output at setup.
Sensor power drops
below 4.75 VDC and
< Err 5V > is displayed
(instead of a value).
All Outputs are Off.
Supply power failure is
detected and
< Err PWR > is
displayed (instead of a
value).
All Outputs are Off.
Specified Voltage Ranges for Sensors
Table 10 provides the specified operating voltage range for System 450 sensors. To
determine if a sensor is operating in the specified range, measure the voltage
between the sensor's terminal connections at the System 450 control module (the
Sn1, Sn2, or Sn3 terminal and one of the C terminals).
If the voltage is out of the specified range, check the sensor wiring for shorted or
open circuits. Repair or replace wiring as needed. If the wiring appears to be in
good condition, replace the sensor and retest the voltage and operation.
System 450™ Series Modular Control Systems with Standard Control Modules Technical Bulletin
Possible Cause
Solution
Sensor, sensor
Check and the verify integrity of sensor wiring
wiring, or sensor
and connections. Measure the voltage between
connections may
the sensor terminal (Sn1, Sn2, or Sn3) and the
have failed to open or
low-voltage common (C) terminal (with the
close.
sensor connected). See Table 10 for the sensor's
expected voltage range. If the sensor wiring and
sensor connections are good, replace the sensor
and recheck the voltage.
The +5 VDC output is
Check the voltage between the +5 VDC (5V)
out of the specified
terminal and any one of the common (C)
range; the output
terminals. The specified voltage range is +4.8 to
may be shorted to
+5.2 VDC. If the specified voltage is out of range,
ground at the wiring
check the primary supply voltage. (See the
or an active humidity
solution that follows.)
or pressure sensor
If the primary supply voltage is in range, remove
may have failed.
all wiring connection to the 5V terminal and
check the voltage between 5V and any C
terminal. If the voltage is still out of range,
replace the control module.
If the voltage is in range (+4.8 to +5.2 VDC),
reconnect each sensor one at a time to
determine which sensor is causing the voltage
drop. Replace the faulty sensor and recheck the
output voltage.
Supply power failure;
Check the supply voltage to the C450 power
supply voltage is too
module. The measured voltage must be between
low or too high.
100 and 130 VAC at the 120 VAC terminals, or
between 200 and 260 VAC at the 240 VAC
terminals. If the System 450 control system is
powered by an external 24 VAC power supply,
the voltage must be between 20 and 30 VAC.
Bring the supply into range.
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