10
Basic Controls—System 350 P352AB Electronic Pressure Control Series Product/Technical Bulletin
g.
If the control is in the RA mode
, adjust the
setpoint setting to a value higher than the
observed gauge pressure. If the LED is not lit,
turn the setpoint adjustment knob clockwise
until the LED lights.
h. With the LED lit, slowly turn the setpoint
adjustment knob counterclockwise (to
decrease the setpoint setting) until the LED
goes off. Observe the gauge pressure, which
should be the same as the setpoint setting
when the LED went off.
i. Next turn the setpoint adjustment slowly
clockwise until the LED lights again. Observe
the gauge pressure, which should be equal to
the setpoint setting minus the differential
setting.
5. Check the stage modules for proper operation.
Perform Steps 1-4 first.
If stage modules are not used, proceed to Step 6.
a. Determine and record if the stage module
is in the DA or RA mode of operation.
b. Determine the differential setting.
c. Observe and record the offset setting.
d. Observe and record the system
pressure at the gauge.
e. Use the procedure outlined in Steps 4a-4i to
determine if the stage module is operating
properly. Use Table 4 to determine what the
On and Off setpoint pressure values are for
each module.
f. If a stage module LED and relay do not
perform as expected, adjust the differential
and offset potentiometers to their minimum
value and repeat the previous checks.
g. If a stage module still does not perform
properly, replace the stage module.
6. Check the display module for proper
operation.
If there is no display module in the system, skip
this step.
Perform Steps 1-5 first.
a. Check the gauge pressure (psi) at the
transducer.
b. If the display module does
not
display the
(approximate) pressure measured at the
gauge, replace the display module.
c. Pressing the button on the display module
should display the current setpoint setting.
If the displayed setpoint is out of the control’s
setpoint pressure range (check scale-plate at the
setpoint knob for control’s pressure range),
replace the control.
Table 4: S352A Stage Module Relay Troubleshooting
Operating Mode
LED
N.O. Contact
Position
Setpoint Setting Equals
Approximately…
Direct Acting (DA)
On
Closed
(psi reading)
-
offset
-
differential
Direct Acting (DA)
Off
Open
(psi reading)
-
offset
Reverse Acting (RA)
On
Closed
(psi reading)
+
offset
+
differential
Reverse Acting (RA)
Off
Open
(psi reading)
+
offset
R
epairs and Replacement
Field repairs or calibration must not be made.
Replacement controls and pressure transducers are
available through your local Johnson Controls
representative.