sensor signal which can cause nuisance trips or even
damage to the module itself. Observe these precautions:
1. Sensor leads must be replaced with a shielded cable.
The shield should extend from the Sentronic module
to the female sensor connector and should be
grounded only at the module end.
2. The Sentronic module has a good grounding source
when mounted to the compressor. When it is remote
mounted, it must have sufficient grounding area to
minimize the effects of high-level electrical transients
and secondary lightning effects. A metal enclosure
with minimum mounting surface area of 75 sq. in. is
required.
3. Emerson makes available an optional 10' shielded
cable designed especially for the Sentronic. The cable
is grounded per instruction 1.
Field Installation Checks
Before installing Sentronic, determine if the existing oil
pump is equipped with the plug fitting for mounting the
sensor. If not, order the Sentronic Oil Pump Kit.
All Sentronics can be used to replace conventional
capillary tube style oil pressure controls in the field.
Earlier four and five terminal Sentronics (see Fig. 2) were
electrically reset oil pressure switches. They were wired to
have power to reset! The current Sentronic requires no
power to reset and may be directly mechanically and
electrically interchanged with any mechanical oil pressure
switch.
If the Sentronic module is to be remote mounted from the
compressor and/or its sensor leads are to be routed along
with other voltage lines, the Sentronic Remote Mount
Instructions must be followed.
Wiring differences exist from one system manufacturer’s
unit to another. If wiring modifications are unclear, consult
a certified electrician. No wiring modifications are required
for compressors using solid state motor protectors.
Start-Up Quick Checks
Checking The Sensor
Unplug the sensor and start the compressor.
Simultaneously measure the oil pump differential pressure.
Monitor the two terminals at the back of the sensor with an
ohmmeter or continuity measuring set. If the differential
pressure is below the range of 7 to 9 PSID, the sensor
circuit should be open (no continuity, infinite resistance). If
the pressure is above 12-14 PSID, the sensor circuit
should be closed.
Checking the Installed Sentronic Module*
Shut off the compressor. Unplug the sensor. Verify the
module is powered by reading control voltage between the
208-230/240 (or 115/120) terminal and the L (or 2 if
separate control is used) terminal.
Start the compressor with the sensor unplugged. Recheck
to make sure the module voltage is still present. After 120
seconds ±15 seconds, the L-M contact should open and
shut off the compressor.
With the module off on oil pressure, wait 2 minutes and
press the reset button. Module power is required to reset
the 4 and 5 terminal Sentronics. The contactor should
close and start the compressor.
*NOTE: More complete step-by-step procedures for bench
and system Sentronic checks are included on pages 7 and
8 of this bulletin.
Sentronic Specifications
Cut-Out 7-9 PSID
Cut-In 12-14 PSID
Time Delay 120 Seconds ±15 Seconds
Max Control 720 VA; 120/240V
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