4.3.3. Delayed intermittent control


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Fig. 4.3: Op. diagram of delayed intermittent control
A pressure switch or contact manometer works in conjunction with a timer and controls the compressor independently of system pressure.

The compressor goes through the modes of Operating mode ( L2 ), Idle mode ( L1 ) and Stopped ( L0 ). The modes are linked with each other via the timer tV .
The delayed intermittent control combines the benefits of intermittent control and idling control. It is a middle path with lower energy consumption than the idling control method.

The delayed intermittent control operates with two switching variants:

1st Variant
    • The system pressure pN rises to cut-out pressure p max .
      The compressor switches to idle mode ( L1 ).
    • The system pressure pN has not reached cut-in pressure p min after expiry of the time tV .
      The compressor switches to stopped ( L0 ).
    • System pressure pN drops below cut-in pressure p min .
      The compressor switches to       operating mode( L2 ).
2nd Variant
    • The system pressure pN rises to cut-out pressure pmax.
      The compressor switches to idle mode ( L1 ).
    • System pressure pN reaches cut-in pressure p min before expiry of the time tV .
      The compressor switches to operating mode ( L2 ).

There are 2 possibilities to activate the timer tV :

1. Switching on the compressors ( p min ) starts the timer t V .
This provides shorter idling times and therefore lower
energy costs as with 2.

2. On reaching the cut-out pressure ( p max ) the timer tV starts.