A421 Series Standard Electronic Temperature Controls Installation Instructions
6
Replacing an A419 Control with an A421 Control:
Terminal Locations and Labels
The A421 Series Electronic Temperature Controls are
the next generation of the A419 Series Electronic
Temperature Controls.
If you need to replace an A419 control with an A421
control, be sure to note that wiring terminals on the TB1
and TB2 terminal blocks on A421 controls are in
different positions and have different terminal labels
from the wiring terminals on the A419 controls. Table 3
provides a cross-reference for matching the terminal
labels on A419 controls to the terminal labels on A421
controls.
Note:
The low-voltage signal terminals on the TB3
terminal block are labeled the same on both A419
controls and A421 controls.
See Figure 4 for terminal block and terminal positions
on the A421 control.
TB2
LC
Line-Voltage SPDT Relay Common Contact:
Connect power supply to
power the controlled load.
Connect 24 VAC (hot) for 24 VAC applications.
Connect 120 VAC (hot) for 120 VAC applications.
Connect L2 for 208/240 VAC applications.
28 AWG to 12 AWG
0.08 mm
2
to 4.0 mm
2
LNO
Line-Voltage SPDT Relay Normally Open Contact:
Connects controlled
equipment to the Line-Voltage Normally Open (LNO) contact on the SPDT
relay. When LC is closed to LNO, the relay is energized and the green LED
is on. The LNO terminal typically provides power to the controlled
equipment in both cooling and heating applications.
LNC
Line-Voltage SPDT Relay Normally Closed Contact:
Connects
controlled equipment to the Line-Voltage Normally Closed (LNC) contact
on the SPDT relay. When LC is closed to LNC, the relay is de-energized
and the green LED is off. The LNC terminal is not typically wired to the
controlled equipment.
TB3
BIN
Detects a switch closure between the BIN and COM terminals and enables
the selected temperature setback (tSb) value.
22 AWG (0.34 mm
2
)
stranded, shielded
cable recommended
COM
Connects low-voltage common from the sensor and binary input.
SEN
Connects low-voltage input signal wire from control sensors.
Table 2: A421 Control Wiring Terminals and Wire Size Information
Terminal
Block
Label
Description, Function, and Requirements
Recommended
Wire Sizes
Table 3: A419 and A421 Wiring Terminal Labels
Terminal
Block
A419 Terminal
Label
A421 Terminal
Label
TB1
(24 VAC)
T1 LN
T2 24V
TB1
(120/240 VAC)
120
120V
240
240V
AC COM
LN
TB2
(All Voltages)
C
LC
NO
LNO
NC
LNC
