MAY “LEAK” ENOUGH POWER, WHILE “TIMING OUT”,
TO ENERGIZE THE SENTRONIC EVEN THOUGH
THERE MAY NOT BE ENOUGH “LEAKAGE” TO CLOSE
THE COMPRESSOR CONTACTOR. THIS CAN CAUSE A
PREMATURE SENTRONIC TRIP. If there is doubt, the
circuit should be checked before placing it in operation.
The Sentronic Module
The Sentronic has in addition to the (N.C.) contact, used
for compressor shutdown, a Normally Open (N.O.) contact
that can be used in an alarm circuit (See Diagram 4A).
The Single Pole Double Throw (S.P.D.T.) contact of
Sentronic can be electrically isolated from the control
circuit power supply and used to control a circuit with a
different voltage (See Diagram 6).
Sentronic has a timing circuit that actually compares the
amount of time with good oil pressure to that with
insufficient oil pressure and has a memory that will shut the
compressor down after a period of more than two minutes
if the compressor has a “history” of oil pressure fluctuations
with more unacceptable than acceptable pressures.
Sentronic also has a memory that retains the compressor
oil pressure “history” for up to one minute in the event of a
power loss.
Sentronic uses a permanent magnet integral with the reset
button to reset its output control relay in the event of a trip.
When the reset button is depressed, it magnetically pulls
the Sentronic relay's armature to its original, reset position.
Sentronic needs no voltage present to reset.
Installing Sentronic
All OEM Copeland® compressors with oil pumps shipped
after September 1986, have a plug fitting in the oil pump
for mounting the sensor. The oil pump is designed to
accept either the Sentronic sensor or a capillary tube for
the traditional mechanical oil pressure control.
To Install the Sensor, Figure 1:
1. Remove the plug fitting from the oil pump housing.
Discard the copper washer from under the head of the
plug fitting.
2. Install a new O ring into the groove on the sensor. Use
refrigeration oil to pre-lube the O ring before
installation. Use care not to cut the O ring.
3. Install a new copper washer under the hex flange of
the sensor. Do not reuse the copper washer removed
with the plug fitting. Screw the sensor into the pump
body. Torque the sensor to 60-65 Ft./lb.
To Install the Module, Figure 1:
4. When using the bracket above the oil pump use two
10-32 pan head slotted screws with washers. The
maximum screw length is .265 plus bracket thickness.
Longer screws could damage the circuit board.
5. Plug the cable from the module into the end of the
sensor. Care should be taken not to wrap the cable
around a current carrying conductor.
Hi-Potting: Excessive hi-potting can cause damage to the
Sentronic module. Emerson hi-pots the module as part of
final processing. If hi-potting is required, we recommend it
to be limited to single time.
Electrostatic Painting: Static electricity discharges from
electrostatic painting can damage the Sentronic module.
We recommend that the module not be mounted until such
painting is completed.
Remote Mounting the Sentronic Module
The Sentronic sensor sends a low voltage signal to the
Sentronic module. When the Sentronic module is mounted
on the compressor the sensor will normally experience no
disturbance from nearby electrical sources. The radiating
power sources that can cause problems are almost always
in grounded metallic enclosures. However, if the Module is
located remotely from the compressor, and the sensor
leads are extended, and/or routed along with other wiring,
provisions must be made to prevent interference with the
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