16
3.5 PRESSURE SWITCH ADJUSTMENT
Locate the pressure switch as shown in Figure 3.5-1.
The pressure switch can be adjusted using the follow-
ing procedure:
1. Open, lock and tag the main electrical disconnect.
Do not adjust the pressure switch with power on or
machine operating.
2. Remove pressure switch cover by turning the cover
screw counterclockwise.
NOTE: It is required that the load or on-line pressure
be set first, before the unload or off-line pressure is
set.
3. Set the on-line pressure by turning screw 5 (See
Figure 3.5-2).Turn clockwise to increase setting or
counter-clockwise to decrease setting (indicated by
pointer 4).
FIGURE 3.5-1 PRESSURE SWITCH LOCATION
FIGURE 3.5-2 PRESSURE SWITCH ADJUSTMENT
PRESSURE SWITCH
5
2
3
4
4. Set the off-line pressure by turning screw 2.Turn
screw counter-clockwise to increase setting or clock-
wise to decrease setting (indicated by pointer 3).
CAUTION:
DO NOT EXCEED MAXIMUM DISCHARGE PRES-
SURE (LOCATED ON COMPRESSOR DATA
PLATE).
5.Turn power back on, start compressor and test
adjustment(s) made. If necessary, readjust according
to steps 1-4 above.
3.4 CAPACITY CONTROL
On Line/Off Line With Automatic Start/Stop
Control
The compressor will deliver air at full capacity, (the
compressor maximum efficiency condition) or will
operate at zero capacity with high receiver pressure
(the compressor minimum power condition), while the
unit continues to run.
When the compressor starts and line pressure is
below the lower setting of the line pressure switch,
control solenoid 1SV will be energized (closed), inlet
valve will open, and the compressor will load.When
the line pressure reaches the upper setting of the
pressure switch, the compressor will unload by de-
energizing (opening) 1SV and closing the inlet valve.
Solenoid 1SV relieves the internal pressure of the
compressor back to the inlet filter.The only adjustment
required is setting of the pressure switch.
A time delay relay is energized and begins to time out.
The timer, mounted in the control box, is factory set at
10 minutes. It will continue to operate for as long as its
time setting, after which a relay contact opens to de-
energize the compressor starter coil. At the same
time, an amber light (1LT) on the control box is lit to
indicate the compressor has shut down automatically
and will restart automatically.The automatic restart will
take place when the line pressure drops to the lower
setting of the pressure switch. Adjusting the
Auto/Restart timer below the 10 minute factory
setting may shorten the life of the compressor
drive motor.
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