Omega PSW-850 manual Part II Adjustments, Part III Replacements, Replacement of Switches

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.

Part II - Adjustments

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

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%

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.

Part III - Replacements

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.