A421 Series Standard Electronic Temperature Controls Installation Instructions
7
Setup and Adjustments
Front Panel
The front panel of the A421 Series Electronic
Temperature Control has a simple LCD and a
three-button user interface (Figure 5).
Liquid Crystal Display
The A421 Series Control has a backlit LCD screen
(Figure 5). The LCD brightness is adjustable. During
normal operation, the LCD
displays the Main screen,
which provides following information:
•
the temperature sensed at the A99 sensor
•
the selected temperature units (°F or °C)
•
the mode of operation (Flame = Heating mode,
Snowflake = Cooling mode)
•
Binary Input status (BIN) when a (user-supplied)
binary input (switch) is connected and closed to
enable the temperature setback feature.
During setup and adjustment, the LCD displays the
parameter code screens and the parameter value
screens. See the
on page 9 for more information.
Three-Button Touchpad
The touchpad has three buttons for setup and
adjustment of the A421 control (Figure 5). See
on page 9 for more information
on using the three-button touchpad.
Relay Status LED
The green LED on the front panel illuminates when the
SPDT output relay is energized and the
LC
and
LNO
contacts are closed. See Figure 5.
Parameter Codes and Modes of Operation
Relay Off Temperature
(
OFF
)
:
Select the temperature
at which the output relay de-energizes, the LC to LNO
relay contacts open (cutout), and the green LED goes
off. The range of usable temperature values is
-40 to 212 °F (-40 to 100 °C) in 1° increments.
Relay On Temperature
(
On
)
:
Select the temperature
at which the output relay energizes, the
LC to LNO
relay contacts close (cut in), and the green LED lights.
The range of usable temperature values is
-40 to 212 °F (-40 to 100 °C) in 1° increments.
Heating or Cooling Mode of Operation:
When you
select your desired
On
and
OFF
values, the control
automatically determines the mode of operation and
displays the proper mode icon on the Main screen.
Note:
The A421 Series controls do
not
have jumpers
for setting up the heating or cooling mode.
The heating or cooling mode is determined by the
On
and
OFF
value relationship as follows:
•
OFF > On
= Heating mode = Flame icon
•
OFF < On
= Cooling mode = Snowflake icon
Anti-Short Cycle Delay
(ASd):
Select the minimum
time that the output relay remains off (de-energized)
before the next on-cycle can start. The ASd interval
overrides any load demand (On) and does not allow
the output relay to go on until the selected ASd interval
has elapsed. See Figure 6.
Figure 5: A421 Control Front Panel with LCD
and Three-Button User Interface
IMPORTANT:
During normal operation, just the
On
value or just the
OFF
value on the A421 control
changes the differential between
On
and
OFF
, and
can potentially change the mode of operation from
heating to cooling or cooling to heating. To maintain
a constant differential between
On
and
OFF
, you
must adjust both the
On
value and
OFF
value by an
equal number of degrees; or set up the control in the
Restricted Adjustment Mode. See
Restricting User
Adjustment
.
Figure 6: Anti-Short Cycle Delay
