Anti-Short Cycle Delay (Asd); Sensor Failure Mode (Sf); Temperature Units (Un); Low Temperature Stop (Lts) - Penn A421 Series Installation Manual

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 the following figure.
Anti-short cycle delay is typically used for refrigeration applications so that the system
pressure can equalize before restarting the compressor.
Note: When the ASd value is greater than 0, the delay interval initiates every time that the
A421 Control powers 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. You can set the ASd interval from 0 minutes to 12 minutes, in 1 minute
increments.

Sensor Failure mode (SF)

Select whether the control's output relay operates as 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 preferred temperature scale for your application. Select either the Fahrenheit (°F)
or Celsius (°C) temperature scale.
Note: After you change 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 12).
See Restricting user
10 A421 Series Electronic Temperature Controls with Off-Cycle Defrost Installation Guide
Figure 6: Anti-short cycle delay (ASD)
adjustment.