A421 Series Standard Electronic Temperature Controls Installation Instructions
13
•
102 and 132 VAC for 120 VAC applications
•
177 and 264 VAC for 208/240 VAC
applications
d.
If the voltage reading is not within the required
range, check the power source and input
power wires for problems.
2.
Check for proper sensor operation.
a.
Disconnect all power sources to control.
b.
Using an accurate thermometer, take a
temperature reading at the sensor location.
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 2b.
e.
Consult Figure 12 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 Figure 12, proceed to Step 3.
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 correct, replace the sensor.
3.
Check the A421 for proper operation.
Note:
Perform Troubleshooting Steps 1 and 2 before
performing this step.
a.
Disconnect the load from the output relay
terminals.
b.
Ensure that the Parameter Adjustments jumper
is installed, so that access to adjust
parameters is unrestricted.
c.
Reconnect the sensor leads and supply power
to the control.
d.
Replace the cover.
e.
Check the control settings for proper values.
f.
Press
MENU
until
On
appears. Press
MENU
again to display the
On
value.
g.
Press
and
to change the
On
temperature
above and below the sensor temperature until
the relay energizes and de-energizes.
Note:
If the anti-short cycle delay is set to a value
other than 0 minutes, when the control is powered On,
the relay does not energize until the time delay has
elapsed.
h.
If the output relay does not perform as
expected, replace the A421 control.
i.
If proper operation of the A421 control is
verified, reconnect the load and consult the
equipment manufacturer’s instructions for
troubleshooting the controlled equipment.
Repair Information
Do not attempt to repair or recalibrate the A421
temperature control. In case of a defective or
improperly functioning control, contact your nearest
Authorized Johnson Controls/PENN Distributor or
Sales Representative.
When contacting your Johnson Controls/PENN
Distributor, have the model number of the control
available. This number can be found on the label inside
the cover of the control.
Figure 12: Temperature versus Sensor
Resistance
