Johnson Controls P70 Mode D'emploi page 9

Limited Knob Adjustment
Some control models are supplied with Limited Knob
Adjustment, which limits adjustments to the pressure
control and help to deter over-adjustment or
tampering.
To lock the differential setting and allow limited
adjustment of the low event and high event setpoints,
install the knob on the range screw.
To lock the high event setpoint and allow limited
adjustment of the low event setpoint (on All-Range
controls) or differential setting (on MICRO-SET
controls), install the knob on the differential screw.
To install the Limited Knob Adjustment:
1. Adjust control pointers to desired high event and
low event setpoints (on All-Range controls), or
differential setting (on MICRO-SET controls).
2. Place spacer on the proper adjustment screw.
•
All-Range controls (with Limited Knob
Adjustment) have round and knurled
adjustment screws—the spacer must always
be placed on the range screw.
•
MICRO-SET controls have square adjustment
screws, always place the spacer on the same
adjustment screw as the knob.
3. Place the indicator plate as shown in Figure 10, to
lock either the range screw or differential screw in
the desired setting.
4. Install the knob on the other adjustment screw,
and tighten the setscrew. A stop on the bottom of
the knob limits screw adjustment to less than one
turn.
Figure 10: Installing Limited Knob Adjustment Kit
8 P70, P72, and P170 Controls for Low Pressure Applications Product/Technical Bulletin
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Checkout Procedure for Low Pressure
Cut-out Controls
Use the following procedure to check control operation
on a typical low pressure cut-out application.
1. Check the product label on the inside of the
2. Attach a reliable gauge to the suction service port
3. Slowly front seat the suction valve and allow the
4. Slowly back the suction valve off the front-seated
5. Adjust settings as needed. (See Figure 9.) Repeat
IMPORTANT:
IMPORTANT:
Manual Reset Operation
Pressure controls with the Manual Reset option lock
out when they reach cut-out pressure and must be
manually reset by the user to restart the controlled
equipment. The manual reset mechanism is "trip-free"
and cannot be over-ridden by blocking or tying the
reset button down.
On equipment with locked out controls, first determine
and remedy the cause of the lockout, and allow the
sensed pressure to return to the cut-in setpoint. Then
press and release the reset button on the front of the
control to restore operation of the controlled
equipment.
control cover, for model number and switch action.
(See Table 1 for low and high events that
correspond to control model and switch action.)
and run the system at normal conditions.
low side to pump down. Observe the control's low
event switching pressure on the gauge.
position and allow the low side pressure to rise.
Observe the control's high event switching
pressure on the gauge.
checkout procedure if necessary.
Use the pressure control settings
recommended by the
manufacturer of the controlled
equipment. Do not exceed the
pressure ratings of the controlled
equipment or any of its
components when checking
pressure control operation or
operating the controlled
equipment.
After adjusting control settings
and before leaving installation,
cycle the controlled system
several times (at least three) at
normal operating conditions. Use
reliable pressure gauges to verify
proper control settings and
equipment operation.