Chicago Pneumatic CPF 175, Instruction Book

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Regulating system
The compressor is controlled by electronic regulator (1).
The regulator keeps the net pressure within programmable pressure limits by automatically loading and
unloading the compressor depending on the air consumption. It also protects the compressor and monitors
components subject to service.
Unloading
If the air consumption is less than the air delivery of the compressor, the net pressure increases. When the net
pressure reaches the upper limit of the working pressure (unloading pressure), solenoid valve (5) is de-
energized by the electronic regulator (1). The plunger of solenoid valve (5) moves downwards by spring force:
Phase Description
1 The plunger of solenoid valve (5) shuts off the supply of receiver pressure towards
chamber (2).
2 Control pressure present in chamber (2) is vented to atmosphere. Plunger (3) of blow-off
valve (4) is moved by air receiver pressure allowing air receiver pressure to chamber (6).
3 Valve (7) is pushed upwards closing off the air inlet.
4 A small flow of air remains drawn in via channel (8), and is finally blown from receiver via
channel (10) to the air inlet.
5 Air delivery is stopped (0%), the compressor runs unloaded while chamber (6) contains a
steady overpressure (receiver unload pressure minus Blow Off valve (4) pressure drop).
Loading
When the net pressure decreases to the lower limit of the working pressure (loading pressure), solenoid valve
(5) is energized. The plunger of solenoid valve (5) moves upwards against spring force:
Phase
1 The plunger of solenoid valve (5) opens the supply of receiver pressure towards chamber
(2). Plunger (3) of blow-off valve (4) moves, closing off the air pressure supply towards
chamber (6).
2 Valve (7) moves downwards since the pressure in chamber (6) drops below atmospheric
pressure, opening the air inlet to the compressor element.
3 Air delivery is resumed (100%), the compressor runs loaded while the piston-rod-valve
assembly is only surrounded by atmospheric pressure.
2.5 Energy recovery system
General description
The maximum allowed pressure at the water side of the heat exchanger is 10 bar (145 psi).
When the energy recovery system is not used, make sure that all water is out of the energy
recovery system.
The energy required in any compression process is mainly transformed into heat. The major part of the
compression heat is dissipated through the oil system. The energy recovery systems are designed to recover
Instruction book
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