Product Overview

A421 Series Standard Electronic Temperature Controls with and without Power Cords Product Bulletin
5
A421 Control User Interface
Front Panel
The LCD allows you to view the status, parameters,
temperature units, operating mode icons (flame =
heating mode; snowflake = cooling mode),
temperature, units, and binary input.
A three-button touchpad on the front panel allows you
to set up the parameters and adjust the control. The
menu button allows you to save the values and
advance to the next parameter.
A green LED indicator reports the status of the output
relay.
Backlight Brightness Level
The backlight brightness level feature allows you to
adjust the LCD backlight intensity. At level 0 the
backlight is off. Level 10 is the brightest backlight
setting and the system default. The selected backlight
brightness level is applied to the LCD during normal
operation. When you enter the programming menus to
set up the control or press any key, the LCD
automatically goes to the brightest level. If no key is
pressed for 30 seconds the main screen is displayed
and the backlight setting reverts to the level you
selected.
SPDT Relay Output
The terminals on the TB2 terminal block are connected
to an SPDT dry-contact relay in the A421 control. The
A421 Electronic Temperature Control can be wired to
use the same power source to power the control and
power the controlled load. The control can also be
wired to control the relay based on the On/OFF
temperature values.
Relay De-energized (Off) = LC open to LNO (as
shown in Figure 11) and the relay status LED is off
Relay Energized (On) = LC closed to LNO and the
relay status LED is on
Basic and Advanced Programming Menu
The A421 Series controls have a Basic adjustment and
an Advanced setup and adjustment menu.
You use the Advanced menu for initial setup of control
and adjustment of the advanced A421 control features.
The Basic menu allows you to set up simple
applications, and quickly and easily adjust the
temperature On and Off values and other basic
features.
In Restricted Adjustment Mode, users cannot access
either the Basic or Advanced menu, and can only
adjust the temperature within the defined adjustment
range. See Restricted Adjustment Mode
for more
information.
Switch-Activated Temperature Setback
The Temperature Setback feature allows you to
establish setback temperature On and Off values. The
A421 controls load to these effective setback values
when the user-supplied switch closes the binary input
control circuit, the LCD displays BIN in the upper-right
corner. The temperature setback is enabled and the
control uses the On/Off setback values to control the
output relay.
Figure 10: A421 Series Control Front Panel with
LCD Display
Figure 11: TB2 Terminal Block Showing
Connections to the Internal SPDT Relay