INSTALLATION, START-UP & MAINTENANCE MANUAL
SD-220 TO SD-600
REV 04 – 10 Oct 2003
Page 13 of 32
3.2.2. Dryer Operating Sequence
The Sullair SD-220-DDS to SD-600-DDS heatless air dryers use a PLC as the standard
controller. In the event of a power failure, the inlet valves remain in their position, and the
exhaust valves will close and dryer will pressurize both chambers. When power is
restored, the dryer will return to the same step in the cycle it was in before power was lost.
Energizing control panel: Power is turned ON – electrical circuit is energized.
When power is applied or restored to the control panel, the dryer will remain in a standby
state for one (1) minute period, allowing the dryer system to repressurize.
STEP 1 SELECT LEFT CHAMBER DRYING.
- De-energize solenoid EV-1R and EV-2L.
- Energize solenoid EV-1L and EV-2R.
- Inlet valve positioned for left chamber drying.
- Exhaust valve opened for right chamber regeneration.
- When regeneration time is complete, go to STEP 2
STEP 2 RIGHT CHAMBER REPRESSURIZATION.
- De-energize solenoid EV-1L and EV-2R.
- Inlet valves remain in open position.
- Right chamber exhaust valve closes.
- The repressurization timer starts a countdown of 45 sec.
- When repressurization time is complete, go to STEP 3
STEP 3 SELECT RIGHT CHAMBER DRYING.
- Energize solenoid EV-1R and EV-2L.
- Inlet valve positioned for right chamber drying.
- Exhaust valve opened for left chamber regeneration.
- When regeneration time is complete, go to STEP 4
STEP 4 LEFT CHAMBER REPRESSURIZATION
- De-energize solenoid EV-1R and EV-2L
- Inlet valves remain in open position.
- Left chamber exhaust valve closes.
- The repressurization timer starts a countdown of 45 sec.
- When repressurization time is complete, go to STEP 1
The dryer has completed one (1) full cycle and will repeat steps 1 through 4 until power is
disconnected from the control panel.
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