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2. Check for proper sensor operation.
Figure 14, Nominal Temperature vs. Sensor Resistance
Check the A419 for proper operation.
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b) Use a reliable AC voltmeter to check the voltage between the COM and I20V or
240V terminals on line voltage models and the two 24V terminals on low-voltage
models. Refer to the wiring diagrams furnished with the unit.
c)
The voltage must be between 20 and 30 VAC for 24 volt applications, 102 and 132
VAC for 120 volt applications, 177 and 264 VAC for 208/240 volt applications
If the voltage reading is within the required range, proceed to Step 2.
If the voltage reading is not within the required range, check the power source and
input power wires for problems.
a. Disconnect all power sources to control.
b. Take a temperature reading at the sensor location, using an accurate thermometer.
c. Disconnect the sensor from the control.
d. Using an ohmmeter, measure the resistance across the two sensor leads while the
sensor is at the temperature taken in step b.
Figure 14
e. Consult
to verify that the measured temperature and resistance conform
to established temperature and resistance values.
f. If the measured values conform to the values in
g. If the sensor's measured resistance value is substantially different from the
expected value for that temperature, check the sensor wiring. If sensor wiring is
OK, replace the sensor.
Note: Perform Troubleshooting Steps 1 and 2 before performing this step.
a. Disconnect the load from the output relay terminals.
b. Check that the Keypad Lock jumper is installed, so that the keypad is unlocked.
c. Reconnect the sensor leads and supply power to the control.
d. Replace the cover.
Direct Drive Fluid Coolers
Figure 14
, proceed to Step 3.
IOM 1062
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