A421 Series Electronic Temperature Controls with Off-Cycle Defrost Installation Instructions
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4. Or, change the SdF value to 0 during a defrost
cycle and return to normal On/Off operation. See
Figure 10.
Control Behavior When Starting or Stopping an
Automatically Enabled Defrost Off-Cycle
The following behavior is enforced:
• At power up, the initial Defrost Interval (dI) does
not initiate a Defrost Cycle Time (dFt).
• A defrost cycle occurs at the beginning of each
subsequent defrost interval.
• You can start or stop a defrost cycle using the SdF
parameter or Binary Input (BIN).
• Starting a defrost cycle terminates the defrost
interval (dI) and starts a new defrost cycle.
• Stopping a defrost cycle terminates the dFt and
continues the current defrost interval (dI) until the
start of the next regular dI and defrost cycle.
SdF Parameter: To start or stop a Defrost Cycle using
the SdF parameter:
1. Select a Start/Stop Defrost Cycle (SdF) parameter
value of 1.
2. Or, change the SdF value to 0 (zero) during a dFt
to stop a defrost cycle and return the control to
normal On/Off operation. See Figure 11.
Binary Input: To start or stop a Defrost Cycle using the
Binary Input (BIN):
1. Connect a momentary contact switch between BIN
and COM on T3 terminal block.
2. Each time the momentary contact switch is
pressed, the defrost cycle starts or stops
depending on whether the defrost cycle is running
or not. See Figure 11.
Figure 10: Manual Defrost Only: Behavior When dI is Set to 0
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