Control System, Functional Description- Supervisor Controller - Sullair LS-120 series Operators Manual And Parts Lists

guidelines apply to all Series 12 & 16 Series com-
pressors. For explanatory purposes this description
will apply to a compressor with an operating pres-
sure range of 125 to 135 psig (8.6 to 9.3 bar). A
compressor with any other pressure range would
operate in the same manner excepting stated pres-
sures.
START - 0 TO 50 PSIG (0 TO 3.5 BAR)
When the compressor START button is depressed,
the sump pressure will quickly rise from 0 to 50 psig
(0 to 3.5 bar). During this period both the pressure
regulator and the solenoid valve are closed, the
inlet valve is fully open due to inlet air flow, and the
compressor pumps at full rated capacity. The rising
compressor air pressure is isolated from the service
line in this phase by the minimum pressure valve,
set at approximately 50 psig (3.5 bar).
NORMAL OPERATING MODE - 50 TO 125 PSIG
(3.5 TO 8.6 BAR)
When the pressure air rises above 50 psig (3.5 bar),
the minimum pressure/check valve opens and
delivers compressed air to the service line. From
this point on, the line air pressure is continually
monitored by a line pressure gauge and a pressure
switch usually set at 135 psig (9.3 bar). The pres-
sure regulator and the solenoid valve remain closed
during this phase. The inlet valve remains fully open
for maximum capacity.
MODULATING MODE - 125 TO 135 PSIG (8.6 TO
9.3 BAR)
If less than the rated capacity of compressed air is
being used, the service line pressure will rise above
125 psig (8.6 bar). The pressure regulator valve
gradually opens, applying air pressure through the
control line to the inlet valve piston. This causes the
inlet valve to partially close reducing the amount of
air entering the compressor until it matches the
amount of air being used. The control system func-
tions continually in this manner, between the limits
of 125 to 135 psig (8.6 to 9.3 bar), in response to
varying demands from the service line.
The pressure regulator has an orifice which vents a
small amount of air to the atmosphere when the
pressure regulator controls the inlet valve. The ori-
fice also bleeds any accumulated moisture from the
control lines.
UNLOAD - IN EXCESS OF 135 PSIG (9.3 BAR)
LINE PRESSURE
When no air is being used,the service line pressure
rises to the setting (cut-out pressure) of the pres-
sure switch. the pressure switch opens, interrupting
the electrical power to the solenoid valve. At this
time, the solenoid valve allows dry sump tank air
pressure or service air pressure through a shuttle
valve to be applied directly to the inlet valve piston
and keep it closed. Simultaneously, the solenoid
valve sends a pneumatic signal to the blowdown
valve. The blowdown valve opens the sump to the
compressor intake reducing the sump pressure to
approximately 20 psig (1.4 bar). The check valve in
the air service line pressure prevents line pressure
from returning to the sump.
When the line pressure drops to the low setting
(cut-in pressure; usually 100 psig [6.9 bar] on low
pressure ["L"] compressors and 125 psig [8.6 bar]
on high pressure ["H"] compressors, 150 psig [10.3
bar] on ["HH"] compressors, 175 psig [12.0 bar]
["XH"]), the pressure switch closes, re-energizing
the 3-way solenoid valve and allowing the blow-
down valve to close. The re-energized solenoid
valve again prevents pressure from reaching the
inlet valve. The inlet valve is fully open and the com-
pressor delivers full rated capacity. Should the pres-
sure begin to rise, the pressure regulator will
resume its normal function as previously described.
To accommodate varied periods of time when there
are not any air requirements, "Dual-Control" is uti-
lized. This feature allows you to set the compressor
in an automatic position whereby the compressor
will shut down when no compressed air require-
ment is present and restart as compressed air is
needed.
2.7 CONTROL SYSTEM, FUNCTIONAL DESCRIP-
TION- SUPERVISOR CONTROLLER™
Refer to Figure 2-5. The purpose of the compres-
sor Control System is to regulate the amount of air
being compressed to match the amount of com-
pressed air being used. The Capacity control sys-
tem consists of a solenoid valve, regulator valve
and an inlet valve. The functional description of the
Control System is described below in four distinct
phases of operation. The following description text
applies to all 120 and 160 series compressors with
optional Supervisor Controller. For explanatory pur-
poses, this description will apply to a compressor
with an operating range of 100 to 110 psig (6.9 to
7.6 bar). A compressor with any other pressure
range would operate in the same manner except
stated pressures.
START MODE - 0 TO 50 PSIG (0 TO 3.5 BAR)
When the compressor "
depressed, the sump pressure will quickly rise from
0 to 50 psig (0 - 3.4 bar). The compressor initially
starts unloaded, then switches to full load when full
Section 2
DESCRIPTION
" (START) pad is
11