Section II - Description
8
Quincy Compressor-QSI
®
Capacity Control System
As the motor starts driving the compressor rotors, air is
drawn in, compressed and discharged into the air/fluid
reservoir. When the air pressure in the air/fluid reservoir
exceeds the set point of the pilot valve (normally 110
PSIG), the valve opens and passes a controlled volume of
air to the inlet valve air cylinder.
NOTICE!
Other pressures are available optionally.
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.
When maximum pressure (typically 10 PSIG above
normal full load pressure) has been obtained in the air
system, complete compressor unloading occurs. The
pressure switch located in the control panel sends a signal
to the control and the solenoid valve opens, venting the
residual pressure from the blowdown valve. At the same
time, control air from the reservoir check valve is directed
through the solenoid to the inlet valve air cylinder. The
inlet valve is held in a closed position preventing the
intake of air into the compressor and serving as a check
valve preventing reverse air/fluid flow through the inlet
valve and air filter.
Auto/Dual
(Standard)
The Auto/Dual system offers two choices of controlling
the Quincy QSI Compressor. With the selector switch
in the Continuous Run position, the compressor operates
continuously, matching air demand as the differential
pilot valve controls the position of the inlet valve. When
maximum system pressure is reached, the pressure switch
opens, venting the air/fluid reservoir and, although the
compressor continues to run unloaded, no air is com-
pressed.
When the Auto Dual mode is selected, the compressor
will also perform as above; however, a solid state timer is
activated when the pressure switch contacts open. This
timer is adjustable within a ten (10) minute range. When
the timer reaches the end of its delay period, the compres-
sor will automatically shut down and assume a “standby”
mode. Upon a drop in system air pressure, the pressure
switch contacts close, restarting the compressor automati-
cally. The timer should be set, during unit start-up, for a
minimum of six (6) minutes.
During the unloaded/timing mode, if plant pressure
should drop causing the pressure switch contacts to close,
the compressor will continue to operate, resetting the
timer and instructing the inlet valve to reopen.
Summary of Contents for QSI Series
Page 2: ......
Page 7: ...Section I General Quincy Compressor QSI 5 MODEL IDENTIFICATION...
Page 62: ...Section IV Operating Procedures 60 Quincy Compressor QSI 1 Week Timer 2 Remaining Running Time...
Page 79: ...Section IV Operating Procedures Quincy Compressor QSI 77...
