Figure 12: Temperature versus sensor resistance
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. Make sure that the Parameter Adjustments
jumper is installed so that you have unrestricted
access to adjust parameters.
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
Down
or
Up
to change the On temperature
above and below the sensor temperature until the
relay energizes and de-energizes.
h. If the output relay does not perform as expected,
replace the A421 Control.
i. If you verify proper operation of the A421 Control,
reconnect the load and consult the equipment
manufacturer’s instructions to troubleshoot 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.
Ordering information
See Table 5 to order a standard A421 Series Electronic
Temperature Control. See Table 6 and Table 7 for
information about A99 sensors, mounting hardware, and
other accessories you use to install A421 Controls. Contact
your nearest Johnson Controls or PENN distributor or sales
representative to order these products.
Table 5: A421 Series Electronic Temperature Controls
with Cycle Timer selection chart
Product type Description
A421ABT-02C
Line-voltage Type 1 Electronic Temperature
Control with Cycle Timer: Type 1 (NEMA), IP20
standard enclosure for DIN rail and surface-
mount applications. Rated for 120/240 VAC.
Includes timer for On/Off duty-cycle control.
Includes an A99BB-200C temperature sensor
with 6.6 ft (2.0 m) cable.
A421AET-01C
Line-voltage Type 4X Electronic Temperature
Control with Cycle Timer: Type 4X (NEMA),
IP66 watertight enclosure for surface-mount
applications. Rated for 120/240 VAC. Includes
timer for On/Off duty-cycle control. Includes an
A99BB-25C temperature sensor with 9 7/8 in.
(0.25 m) cable.
Table 6: A99 Temperature Sensors selection chart
Product code
Description
A99BA-200C
Positive temperature coefficient (PTC)
Temperature Sensor: Standard probe 2 in. (5.1
cm) with 6.6 ft (2.0 m) shielded polyvinyl chloride
(PVC) cable; ambient operating temperature
range: -40ºF to 212ºF (-40ºC to 100ºC)
A99BB-25C
PTC Temperature Sensor: Standard probe 2
in. (5.1 cm) with 9 7/8 in. (0.25 m) PVC cable;
ambient operating temperature range: -40ºF to
212ºF (-40ºC to 100ºC)
A99BB-200C
PTC Temperature Sensor: Standard probe 2 in.
(5.1 cm) with 6.6 ft (2.0 m) PVC cable; ambient
operating temperature range: -40ºF to 212ºF
(-40ºC to 100ºC)
A99BB-300C
PTC Temperature Sensor: Standard probe 2 in.
(5.1 cm) with 9.8 ft (3.0 m) PVC cable; ambient
operating temperature range: -40ºF to 212ºF
(-40ºC to 100ºC)
A99BB-400C
PTC Temperature Sensor: Standard probe 2 in.
(5.1 cm) with 13.1 ft (4.0 m) PVC cable; ambient
operating temperature range: -40ºF to 212ºF
(-40ºC to 100ºC)
A99BB-600C
PTC Temperature Sensor: Standard probe 2 in.
(5.1 cm) with 19.7 ft (6.0 m) PVC cable; ambient
operating temperature range: -40ºF to 212ºF or
(-40ºC to 100ºC)
A99BC-25C
PTC Temperature Sensor: Standard probe 2 in.
(5.1 cm) with 9 7/8 in. (0.25 m) high-temperature
silicon cable; ambient operating temperature
range: -40ºF to 212ºF (-40ºC to 100ºC)
A99BC-100C
1
PTC Temperature Sensor: Standard probe 2 in.
(5.1 cm) with 3.3 ft (1.0 m) high-temperature
silicon cable; ambient operating temperature
range: -40ºF to 212ºF (-40ºC to 100ºC)
A421 Series Electronic Temperature Controls with Cycle Timer Installation Guide
11
