Install Instructions

A421 Series Standard Electronic Temperature Controls Installation Instructions
8
Temperature Units (Un): Select the desired
temperature scale for your application. Select either the
Fahrenheit (°F) or Celsius (°C) temperature scale.
Note: After changing the temperature units value
(Un), confirm that the temperature values for the other
parameter codes are still correct for your application.
Low Temperature Stop (LtS): Select the lowest
temperature value that the On/OFF control band can
be adjusted to when control adjustment is restricted.
High Temperature Stop (HtS): Select the highest
temperature value that the On/OFF control band can
be adjusted to when control adjustment is restricted.
Restricted Adjustment Mode: The HtS and LtS
values define the restricted adjustment temperature
range and are enforced only when the A421 control is
set to the restricted adjustment mode (Figure 9). See
Restricting User Adjustment
.
Note: We recommend leaving HtS and LtS at their
default values, unless you intend to use the restricted
adjustment mode.
Note: If you use the Temperature Setback feature in
the Restricted Adjustment Mode, the effective On and
OFF setback values (On + tBs and OFF + tBs) can be
greater than the selected HtS value or less than the
selected LtS value.
Temperature Setback (tSb) Select a temperature
value for setting back the On and OFF temperature
values. When a (user-supplied) switch between the
BIN and COM terminals closes:
• the Main screen displays BIN in the upper-right
corner of the LCD.
• the temperature setback feature is enabled and the
control uses the effective On and OFF setback
values (On + tSb and OFF + tSb) to control the
relay.
Note: The control displays only the original On and
OFF values in both the normal and setback modes.
The effective setback On and OFF values (On + tSb
and OFF + tSb) are never displayed on the control
LCD.
The temperature setback adjustment range is from -50
to 50 F° (-30 to 30 C°). Typically, heating applications
require a negative temperature setback (tSb) value,
and cooling applications require a positive value.
Sensor Offset Adjustment (So): Sensor offset allows
you to compensate for any difference between the
displayed temperature value and the temperature
sensed at the A99 sensor. Select a temperature value
to offset the temperature displayed on the LCD from
the temperature sensed at the sensor. The sensor
offset adjustment range is from -5 to 5 F° (-3 to 3 C°) in
1° increments.
Backlight Brightness Level (bLL): 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 selected brightness level.
Table 4: Standard Parameter Setup Codes, Descriptions, Range of Values, and Default Values
Parameter
Code
Parameter Description (Menu) Range of Usable Values Factory Default
Value
1
Un Temperature Units (Advanced only) ºF or ºC ºF
OFF Relay Off Temperature (Basic, Advanced, and
Restricted)
-40 to 212 ºF (-40 to 100 ºC) 25ºF
On Relay On Temperature (Basic and Advanced) -40 to 212ºF (-40 to 100ºC) 30ºF
ASd Anti-Short Cycle Delay (Basic and Advanced) 0 to 12 (minutes) 1 (minute)
tSb Temperature Setback (Advanced only) -50 to 50ºF (-30 to 30ºC) 0ºF
So Sensor Offset Adjustment (Advanced only) -5 to 5ºF (-3 to 3ºC) 0ºF
HtS High Temperature Stop (Advanced only) -40 to 212ºF (-40 to 100ºC) 212ºF
LtS Low Temperature Stop (Advanced only) -40 to 212ºF (-40 to 100 ºC) -40ºF
SF Sensor Failure Action (Basic and Advanced) 0 = output relay de-energized
1 = output relay energized
1 (output relay
energized)
bLL LCD Backlight Brightness Level Adjustment
(Advanced only)
0 to 10; 0 = backlight off,
10 = brightest backlight setting
10 (brightest backlight)
1. The default values for general application A421 models are shown. OEM A421 models may have different default values.