A421 Series Standard Electronic Temperature Controls Installation Instructions
8
Anti-short cycle delay is typically used for refrigeration
applications to allow the system pressure to equalize
before restarting the compressor.
Note:
When the ASd value is greater than 0, the delay
interval is initiated every time that the A421 control is
powered on and every time that an off-cycle begins.
When the ASd interval is activated, the temperature
sensed at the A99 sensor and the parameter code
ASd
flash (alternately) on the LCD. The ASd interval can be
set from 0 to 12 minutes, in 1-minute increments.
Sensor Failure Mode
(SF):
Select how the control’s
output relay operates (energized or de-energized) in
the event of a sensor or sensor wiring failure. When the
control detects a sensor circuit failure, the output relay
operates in the selected sensor failure mode. The LCD
flashes
SF
and
OP
if the sensor circuit is open or
SF
and
SH
if the sensor circuit is shorted.
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
.
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
(Part 1 of 2)
Parameter
Code
Parameter Description (Menu)
Range of Usable Values
Factory Default
Values Shown
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)
25 ºF
