pump function will automatically alternate to
the next available vacuum pump.
• When shutting down the system, to prevent
unwanted starting due to the next in line
alternation feature just described, put the
selector switches to “OFF” for any pumps not
running before the ones that are running.
4A.5 Backup Vacuum Switch Set
Point Adjustments
The backup switch is set at the factory to the
operating point(s) as stated on the wiring diagram
supplied with the unit. It is good practice to cycle
the switch to determine actual operating points
before proceeding with readjustment. Refer to
Figure 4A.4 for location of adjustment.
Adjusting Instructions
1. To make an adjustment, loosen the tamper
resistant set screws (2) on the adjustment
sleeve.
2. Secure the hex body with an open-end
wrench. Hand turn the adjustment sleeve
counter-clockwise to increase and clockwise
to decrease the set point. The backup
vacuum switch should always be set with
falling vacuum level starting at a vacuum
level higher than the setpoint.
3. Using the vacuum gauge determine the
actuation point of the switch.
4. If the actuation point is above the desired
value, turn the adjustment sleeve clockwise
to decrease the actuation point, and if it is
below, turn the adjustment sleeve counter-
clockwise to increase it.
5. For exact vacuum setting, cycle vacuum
switch and make
fi
ne adjustments by
repeating steps 2 through 4 (trial and error
process) until the desired setting is obtained.
6. Secure the tamper resistant set screws (2) on
the adjustment sleeve.
CAUTION
Do not over tighten set screws.
CAUTION
• ALWAYS change vacuum setting gradually.
• ALWAYS check switch setting before
making any adjustments.
• DO NOT force adjustment sleeve when it
becomes di
ffi
cult to turn.
• ALWAYS isolate the vacuum transducer
before making any adjustments to the
backup vacuum switch.
Tamper Resistant
Set Screws (2)
Decrease
Increase
Figure 4A.4 Backup Vacuum Switch
Lubricated Rotary Vane Laboratory Vacuum Systems
4107 9021 88.01
4A-5
