Capacity Control System; Controller Options - Quincy QSI-90 Instruction Manual

Section II - Description

Capacity Control System

As the motor starts driving the compressor
rotors, air is drawn in, compressed and
discharged into the system downstream.
When the air pressure at the service
connection exceeds the set point of the
pilot valve (normally 100 PSIG), it begins to
close the air supply off to the unloader.
The air forces a piston to move within
the cylinder, closing the inlet valve. The
compressor will continue to run, matching
air demand with air delivery by constantly
adjusting the position of the inlet valve.
The inlet valve regulates compressor
capacity between 100% and nearly 0% of
rated delivery.

Controller Options

Standard QSI compressors are equipped
with either an electronic controller with
an HMI control panel which utilizes a
microprocessor to control the compressor
6
When maximum pressure (typically 15
PSIG above normal full load pressure)
has been obtained in the air system,
complete compressor unloading occurs.
The pressure switch Or transducer sends
a signal to the control and the solenoid
valve opens, venting the residual pressure
through the blowdown valve.
or standard controls with a auto dual
operating mode and lights, indicators
and gauges for monitoring compressor
operation.