Omega PSW-850 - Manual (Page 4)

Special Instructions For Vacuum Ranges
On vacuum ranges, the C-NO circuit is closed at sea level
conditions. Therefore, increasing vacuum will cause the C-
NC circuit to close while decreasing vacuum will cause the
C-NO circuit to close. Please make a note of this and
wire/adjust the unit accordingly.
Tools Needed
Screwdriver
NOTE: For set point adjustments and re-calibration, con-
nect control to a calibrated pressure gauge.
PSW-852, PSW-853
Remove cover, follow same procedure as paragraph above.
Switches may be set together or apart, up to 100% of range
scales (maximum separation on models PSW-852A* is
defined in Table 1). On dual switch, either switch may be set
high. On triple switch models, the third (middle) switch has
no over-travel mechanism and must always be set to the
highest pressure when switches are set apart. Altering the
setting of one switch will usually have little effect on the
other(s), however re-calibration may be desired at a critical
pressure setting and after changing switch(es) or sensor.
Table 1
Special Instructions for Models PSW-852A*
When calibrating the Models PSW-852A*, Switch 2 (the
right switch as viewed from the front of the control) must be
set to the lower pressure value. Use a screwdriver to turn the
adjustment screw and obtain the desired actuation pressure
for Switch 2. Switch 1 can then be set following the proce-
dure outlined above for other products. Maximum separa-
tion between Switch 1 and 2 is defined in Table 1.
PSW-855, 856
Controls are factory calibrated for maximum accuracy at the
dial midpoint. Switches may be set together or apart up to
100% of the range scale. On dual switch models either
switch may be set high. On triple switch models, the third
(middle) switch has no over-travel mechanism and must
always be set to the highest pressure when the switches are
set apart. Altering the setting of one switch will usually have
little effect on the other(s), however re-calibration may be
desired at a critical setting or after changing switch(es) or sen-
sor.
To re-calibrate, turn pointer to desired set point and add
gauge pressure until switch transfers. If gauge pressure and
set point pressure do not agree, turn zero adjust screw
clockwise to raise. Counter-clockwise to lower setting.
Tools Needed
Screwdriver
USE ONLY FACTORY AUTHORIZED REPLACEMENT PARTS
AND PROCEDURES. DISCONNECT ALL LIVE CIRCUITS
BEFORE PROCEEDING. COMPONENTS AVAILABLE FOR
REPLACEMENT ARE THE SWITCHES. OTHER COMPONENTS
FACTORY REPLACEABLE ONLY.
REPLACEMENT OF SWITCH(ES)
1) Disconnect leadwires.
2) Remove the two mounting screws. On multi-switch
controls, first remove switch bias springs (See Figure 1.)
3) Insert replacement switch and replace screws and bias
springs.
4) Check switch set point and re-calibrate per PART II if
necessary.
Part III - Replacements
Part II - Adjustments
Model & Range Switch Separation
(% of Range Span)
PSW-852AA (-300 to 0 ”wc VAC) 25%
PSW-852AB (-10 to +10 ”wc) 35%
PSW-852AC (-50 to +50 ”wc) 35%
PSW-852AD (0.5 to 5 ”wc) 50%
PSW-852AE (2.5 to 50” wc) 50%
PSW-852AF (10 to 250 ”wc) 20%