8-1314 PDF
Application
Engineering
Application
Engineering
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AE8-1314 R1
February 2001
Reformatted October 2010
Sentronic+®
Electronic Oil Pressure Control
Introduction and Features
The module control base can accept either threaded or
push-in electrical conduit connections.
The Sentronic+® electronic oil pressure safety control
uses a pressure sensor and an electronic module
to precisely measure oil pump differential pressure.
Common sources of leaks (bellows, capillary tubes,
and pressure connections) are eliminated when using
the Sentronic+.
Basic Control Operation
The oil pressure sensor is mounted directly into the
oil pump of the compressor. The Sentronic+ sensor
measures the oil pump differential pressure and has
an internal contact that opens due to low oil pressure,
causing the Sentronic+ electronic control module to
begin the timing clock.
Another advantage of Sentronic+ is a precise electronic
clock for the two-minute time-out circuit. Traditional
mechanical controls use resistance heaters to
measure the time-out in the event of low oil pressure.
On 208V systems, low ambient temperatures or
brown-out type conditions cause the heater output to
be reduced, thus increasing the time-out period from
two minutes to three minutes or more when low oil
pressure conditions exist. The electronic clock will
always provide a two-minute time-out.
Should the oil pressure fall below 7 to 9 PSID for a
period of two minutes, the Sentronic+ module will open
the normally closed control circuit, which shuts the
compressor off.
The Sentronic+ will also shut the compressor down if
the oil pressure fluctuates between acceptable and low
oil pressure (indicated by an alternating red and green
LED) and records a history of low oil pressure for 60%
or more of a running cycle. In addition, Sentronic+ has
a memory that will retain the oil pressure levels for up
to one minute during a power loss.
The Copeland® Sentronic+ module features a light
emitting diode (LED) to provide a visual indication of
the oil pressure condition. To aid in trouble-shooting,
the cover label has a summary of the LED fault
indications.
A trip of the oil pressure safety switch is a warning
that the system has been without proper lubrication
for too long. Repeated trips of the oil pressure safety
control are a clear indication that something in the
system requires immediate remedial action. On a
well-designed system, there should be no trips of
the oil pressure safety control, and repeated trips
should never be accepted as a normal part of system
operation.
Sentronic+ no longer requires the use of shielded
cables because of an electronic noise suppression
feature.
All Copelametic® compressors that have an external oil
pump (see AE4-1166) require an Emerson-approved
oil pressure safety control. Failure to use an approved
oil pressure safety control will be considered misuse
of the compressor and may void the warranty if the
compressor should fail due to lack of lubrication.
Sentronic+ Control Module
In addition to the normally closed (N.C.) contact
used for compressor shutdown, the Sentronic+ has a
normally open (N.O.) contact which can be used in an
alarm circuit (See Figure 5).
An oil pressure safety control must meet many
requirements for Emerson approval. These
requirements include maintaining the pressure setting
and time delay calibration within close limits over the
widest variation in expected operating conditions.
Safety controls must pass a life test with a minimum
of 200,000 cycles. Controls must be non-adjustable
and must have a manual reset with a 120 second
nominal time delay at rated voltage, have a cut-out
pressure setting of 7 to 9 PSID (Pounds per Square
Inch Differential), and a cut-in pressure of 12-14
PSID. In this case, PSID is the difference between the
crankcase pressure and oil pump outlet pressure.
© 2010 Emerson Climate Technologies
Printed in the U.S.A.
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 different
voltage (See Figure 3).
Installation
All Copeland® compressors with external oil pumps
shipped after September 1986 have a plug fitting in
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the oil pump for mounting the sensor. The external
oil pump is designed to accept either the Sentronic+
sensor or a capillary tube for the traditional mechanical
oil pressure control.
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2. Install the new O ring into the groove around the
sensor. Note: If applicable, replace the aged O
ring with the new one supplied in the kit. Use
refrigeration oil to pre-lubricate the O ring before
installation. Use care not to cut the O ring.
Removing the cover on the module is accomplished by
gently lifting two locking tabs on the lower corners of
the cover and pulling the lower edge of the cover away
from the base. Refer to Figure 1.
3. Use the new copper washer. Do not reuse the
copper washer removed with the plug fitting.
4. Screw the sensor into the pump body. Torque the
sensor to 60-65 Ft.-Lb.
Installation of the cover is accomplished by hooking
the top of the cover down on the three tabs on the top
of the module base and swinging the cover back into
position until the cover release tabs latch into place.
Refer to Figure 2.
Installing the Module
1. When using the bracket above the oil pump,
use the supplied 10-32 pan head slotted screws
with washers. Alternatively, four holes have been
incorporated in the module base to provide the
option of remote mounting. Refer to Figure 7.
The maximum screw length is .265” plus bracket
thickness. Longer screws could damage the
circuit board.
Installing the Sensor
1. Remove the plug fitting from the oil pump housing
(new installations). Discard the copper washer
from under the head of the plug fitting.
2. Plug the cable from the module into the end of
the sensor. Care should be taken to route the
cable away from current carrying conductors.
Excessive hi-potting can cause damage to the
Sentronic+ module. If hi-potting is required, we
recommend it be limited to a single time.
Figure 1
© 2010 Emerson Climate Technologies
Printed in the U.S.A.
Figure 2
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Both Figures 4A (Sentronic+) and 4B (previous
Sentronic) show typical wiring connections and the
similarity of Sentronic+ and Sentronic oil pressure
switches used on three-phase motor compressors.
The module location and conduit lengths should be
chosen to avoid bending of the conduit beyond its
normal range of flexibility.
When the operating and limit controls are closed,
the system is calling for the compressor to run. The
electrical circuit for the Sentronic+ module consists
of a 240 V (120V) connection to the appropriate
terminal and the jumper between 2 and “M” and the
normally closed (N.C.) contact between “M” and “L”.
The compressor contactor circuit is completed by
the normally closed contact between “M” and “L”. If
the module trips the circuit due to low oil pressure,
the N.C. contact between “M” and “L” opens thereby
opening the circuit of the compressor contactor and
the module.
Remote Mounting
The Sentronic+ module sends a low voltage signal
to determine whether the sensor circuit is opened or
closed. When the Sentronic+ module is mounted on
the compressor, the sensor will normally experience
no disturbances from nearby electrical sources.
While the Sentronic+ is not particularly susceptible to
Electromagnetic Field (EMF) interference, it is wise
to keep the cable away from other current carrying
conductors.
Once the Sentronic+ module has tripped, it must be
manually reset to restore operation.
Grounding
The Sentronic+ plus has been designed with a plastic
case, and does not require a ground connection. A
ground screw is provided on the terminal strip for those
installations utilizing a ground wire in the conduit.
Control with Alarm
The alarm circuit as seen in Figure 5 will be activated
when the Sentronic+ trips on low oil pressure. The
normally open (N.O.) contactor between “L” and “A”
will be closed when the module trips thereby activating
the alarm circuitry.
Sentronic+ Specifications
7-9 PSID
12-14PSID
120 seconds + 15 seconds
60-65 Ft.-Lb.
375 VA; 120V
500 VA; 240V
1600 VA; 120 V
3000 VA; 240 V
The Current Sensing Relay Used with Compressor
Inherent Motor Protectors:
A compressor may exhibit nuisance trips if it has an
inherent protector and experiences motor overheating.
The use of a current-sensing relay allows the
compressor to cycle on the internal inherent protector
without affecting the operation of the Sentronic+.
After an overload trip of a compressor with an
inherent protector, the control circuit will still be
closed and the Sentronic energized although the
compressor motor is not operating. The two-minute
timing circuit will activate due to a lack of oil pressure,
and after the 120-second time delay; the oil pressure
safety switch will trip. Even though the compressor
motor cools sufficiently for the internal inherent
protector to automatically reset, the compressor
cannot start until the oil pressure safety control is
manually reset.
Installing external timer
Caution: An electronic timer may be placed in series
with the compressor contactor to force a delay before
each start and prevent possible short cycling. The
timer must be located so it also prevents the Sentronic+
from energizing during the timing period. SOME
INEXPENSIVE TIMERS 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.
This is normally not a problem since the compressor, if
properly applied, will seldom if ever trip on the internal
inherent protector. If it should happen to do so, the
fact that a protector trip has occurred indicates that
the system operation should be reviewed. However,
If there is doubt, the circuit should be checked
before placing it in operation.
© 2010 Emerson Climate Technologies
Printed in the U.S.A.
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Standard Control Circuits
Static electricity discharges from electrostatic painting
can damage the Sentronic+ module. We recommend
that the module not be mounted until such painting is
completed.
Cut-Out
Cut-In
Time Delay
Sensor Torque
Max Control
Max Control
Max Inrush
Max Inrush
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on frozen food or other critical applications where a
product loss may occur, if a compressor shutdown
should occur during the night or a weekend when
the equipment is unattended, it may be desirable to
prevent a possible nuisance trip by means of a current
sensing relay.
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the operating and limit circuit are closed, “LL1” voltage
energizes the compressor contactor coil (CC). When
the compressor contactor closes, it provides the
power, through a control circuit transformer (XFMR),
to energize the Sentronic+. If the Sentronic+ trips, its
contact (“L” to “M”) in the “LL1-LL2” control circuit
opens to de-energize the compressor contactor and
stop the compressor. The Sentronic+ contact (“L” to
“A”) closes to energize an Alarm Relay (AR).
The current sensing Relay is mounted on the load side
of the contactor, senses by induction the full operating
current of one phase of the motor, closes on a rise
above 14 amps, and opens if the load current falls
below 4 amps.
Note that any A.C. voltage up to and including 240
volts may be used. For line voltages greater than 240
V, a step-down transformer (circuit transformer XFMR
in Figure 3) must be used.
Figure 6 uses a current relay (C.S.). When the current
relay is not energized by motor current, its Normally
Open (N.O.) contact opens the circuit that powers the
Sentronic to avoid a nuisance trip.
LED Interpretation
To aid in troubleshooting an oil pressure problem, the
Sentronic+ has an LED as a visual aid. This section
explains the information provided by the LED.
NOTE: On some 550 volt motor-compressors, it may
be necessary to loop the current carrying wire so that it
passes through the current sensing relay twice in order
to increase the metered amperage to close the relay
contacts.
LED Green
Compressor has sufficient oil pressure.
Using a Separate Control Voltage with the
Sentronic+ (Figure 3)
LED Red
Compressor is experiencing insufficient oil pressure.
To supply the Sentronic+ with two separate voltages
(compressor contactor coil and module), remove the
jumper between terminals “2” and “M.” In this diagram,
the separate control voltage is supplied by “LL1” and
“LL2.” The separate voltage powers the compressor
contactor (CC) by means of a remote relay. When the
remote relay is energized, requesting the compressor
to run, its contact (RR), closes to deliver “LL1” voltage
to the operating and limit contacts. If the contacts in
Red/Green LED Alternating
Compressor is experiencing erratic oil pressure
indicating a possible system problem.
No Light
Control Circuit is not energized L or M for light circuit.
L1 L2 L3
120V TERMINAL
CC CC CC
XFMR
TIMING
CIRCUIT
2
LL 1
OPERATING
AND LIMIT
CONTROLS
MOTOR
CC
L
A
AR
AR = ALARM RELAY
RR = REMOTE RELAY
CC = COMPRESSOR CONTACTOR
XFMR = CONTROL TRANSFORMER
SENSOR
Figure 3
© 2010 Emerson Climate Technologies
Printed in the U.S.A.
LL 2
SENTRONIC
M
RR
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Start Up Procedure
© 2010 Emerson Climate Technologies
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Troubleshooting
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With the module off due to low oil pressure, wait two
minutes and press the reset button. Lack of power after
a reset may be due to an external time delay circuit.
Approximate oil pressure can be measured in the
field. Oil pumps are furnished with a Schrader valve
mounted on the oil pump discharge port. To measure oil
pressure, subtract crankcase pressure from discharge
oil pressure.
Checking the Sensor
Unplug the sensor and, start the compressor. The
Sentronic+ module LED should be red. 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 to 14 PSID, the
sensor circuit should be closed.
Checking the Installed Sentronic+ Module
Shut off the compressor. Unplug the sensor. Read the
control voltage between the 240V (or 115V) terminal
and the L (or 2 if separate control is used) terminal to
verify power to the module.
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.
Measure the differential pressure by subtracting the
crankcase pressure from the oil pump outlet pressure.
Sentronic +
Previous Sentronic
USE EITHER 120V
OR 240V TERMINAL
L1 L2 L3
CIRCUIT
L1 L2 L3
230V OR
115V
SENTRONIC
TIMING
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SENTRONIC
2
M
TIMING
CC CC CC
OPERATING
AND LIMIT
CONTROLS
CIRCUIT
MOTOR
L
L
CC CC CC
OPERATING
AND LIMIT
CONTROLS
MOTOR
M
A
SENSOR
CC
SENSOR
CC
CC = COMPRESSOR CONTACTOR
CC = COMPRESSOR CONTACTOR
Figure 4B
Figure 4A
L1
L1
USE EITHER 120V
OR 240V TERMINAL
L3
SENTRONIC
2
L2
M
USE EITHER 120V
OR 240V TERMINAL
TIMING
CIRCUIT
CS
SENTRONIC
(N.O.)
TIMING
OPERATING
AND LIMIT
CONTROLS
2
L
M
A
OPERATING
AND LIMIT
CONTROLS
A
A
L2
= ADDED ALARM LIGHT
CC
CS
L
MOTOR
A
CC
CS = CURRENT SENSOR
CC
A
Figure 5
© 2010 Emerson Climate Technologies
Printed in the U.S.A.
CIRCUIT
CC
Figure 6
6
CC
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Interchangeability with Previous Sentronic Controls
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between the “M” terminal and the “120” terminal.
It should be the same as the electrical outlet
voltage - about 120VAC.
The electronic two minute timing circuit operates
whenever voltage is applied to a Sentronic+, and it
has not tripped. The timing will be interrupted when
oil pressure rises above 12-14 PSID and closes the
Sentronic sensor. Should oil pressure not build up
sufficiently within 120- seconds, the electronic delay
will time out, open its L-M contact, break the control
circuit, and de-energize the compressor contactor to
stop compressor operation.
4. Since there is no connection made to the
pressure sensor, the module sees this as a nooil pressure condition. After two minutes (plus or
minus 15 seconds - dependent on 50 or 60 cycle
frequency) the Sentronic internal timer will “timeout”. The module will trip; the circuit between
“L” and “M” will open, and it will no longer pass
current to the load.
While the compressor is running, if the compressor
net oil pressure falls below the cut-out setting of the
sensor while operating, and does not re-establish
sufficient pressure within an acceptable time, the
time delay circuit will open the L-M contacts, stopping
compressor operation. Once the oil pressure switch
has tripped, it must be manually reset to restore the
system to operation.
5. With the voltmeter connected to terminals “M”
and “120”, the voltage should now read zero
volts because the circuit between “L” and “M” has
been opened through the action of the electronic
circuit.
6. Reset the Sentronic+, then remove voltage from
terminals “120” and “L”. With a small piece of
wire, jumper the female sensor connections at
the end of the black sensor cord attached to the
module. Reapply power to terminals “120” and
“L” and wait two minutes. The module should not
“time-out” after two minutes because jumpering
the sensor connections makes the timing circuit
“see” good oil pressure. The jumper imitates the
action of a small pressure switch located in the
sensor. This switch opens on low oil pressure and
closes on good oil pressure.
IMPORTANT: If a power interruption occurs after an oil
pressure safety trip, wait two minutes before resetting
after power is restored.
Electrical bench checkout procedure
This instruction sheet describes how the Sentronic+
may be easily bench-checked using only a voltmeter
and a 120VAC electrical extension cord.
CAUTION!
Damage to the Sentronic+ module may result if
the “M” terminal of the Sentronic+ is connected to
ground or directly to a voltage line!
7. Measure between the “120” terminal and the “M”
terminal with the voltmeter. The meter should
read full line voltage showing that the circuit has
not opened.
This test is conducted with 120VAC. A shock will
result if the Sentronic+ terminals are touched
when the Sentronic module is energized.
8. To check if the module will operate on 208/240
volts as well as on 120 volts, change the scale
of the voltmeter (if necessary), to read up to
250VAC. Without removing power, measure the
voltage between the “M” terminal and the “240”
terminal. You should read nearly twice the voltage
as that read between the “M” terminal and the
120“ terminal. This is because Sentronic+ has
a small control transformer connected so that
it can accept either 120V or 208/240V. It’s selftransforming action actually enables it to step up
its own voltage. By making this voltage check, the
transformer is being checked.
Use care whenever working with any voltage!
Make sure your electrical outlet is grounded, the
electrical extension cord used has a ground wire,
and the ground wire is connected to the grounding
screw of the Sentronic+ .
1. Apply 120VAC power to the Sentronic+ module
terminals marked “120” and “L”. The Sentronic
should have a jumper in place between terminals
“M” and “2”.
9. If the module successfully passes the above test
sequence it is fully functional. If the module fails
any of the above steps, it is faulty and should be
replaced.
2. Wait two minutes, then push the Sentronic+ reset
button to reset the module and start the timing
circuit.
3. With a voltmeter, measure line voltage (120VAC)
© 2010 Emerson Climate Technologies
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Interchangeability of Sentronic+™ and Sentronic™
modules and sensors
•
Remove the two cable quick connections from
the circuit board
The Sentronic+™ oil pressure control uses both a
new module and a new sensor. The sensors and
module can be made compatible with older generation
components if the following steps are taken:
•
Using pliers, squeeze the strain relief slots and
pull to remove the cable from the module
•
Remove the old module from the compressor
Removing the cable from the new Sentronic+ module:
To use a Sentronic+ module with an older Sentronic™
sensor, the older Sentronic sensor cable must be wired
to the new Sentronic+ module.
•
Remove the cover from the Sentronic+ module
•
Pull the 2 cable quick connects from the circuit
board (these are labeled “Org” and “Red”)
To use an older Sentronic module with a Sentronic+
sensor, the Sentronic+ cable must be wired to the
Sentronic module.
•
Remove the wires from the strain relief (note the
routing of the wires for future reference) and lift
the wires out
•
Remove the wire cable from the module by
twisting the conduit counterclockwise and gently
pulling
There is an older generation Sentronic module which
is fully compatible with the Sentronic+ sensor. It is
supplied with the new (Sentronic+) cable which is
gray for identification purposes, see illustration below.
New Sentronic+
Connecting the old cable to the Sentronic+ module:
Old Sentronic
Connecting the Sentronic+ module to an older
Sentronic sensor
•
Trim approximately 2” of cable sheathing from
the module end of the old cable, taking care not
to nick the wire insulation
•
Feed the wires into the module through the hole
in the bottom of the case
•
Leaving enough lead length to reach the quick
connects, push the wires into the strain relief.
•
Connect the 2 quick-connects to the “ORG”
and “RED” spades. (Note: the connections may
be interchanged; there is no polarity on these
wires). Refer to Figure 7.
•
Install the module to the compressor and make
wiring and sensor connections per the general
instructions.
Removing the cable from the old Sentronic module:
•
Disconnect power to the old module
•
Disconnect the cable from the sensor
•
Remove the cover from the old module
MOUNTING SCREW HOLES
© 2010 Emerson Climate Technologies
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Connecting the older
Sentronic+ sensor
U
Sentronic
L
L
module
to
E
Disconnect power to the module
•
Disconnect the cable from the sensor
•
Remove the cover from the Sentronic+ module
•
Pull the 2 cable quick connects from the circuit
board (these are labeled “Org” and “Red”)
•
Remove the wires from the strain relief by lifting
the wires out
•
Remove the wire cable from the module by
twisting the conduit counterclockwise and gently
pulling
Remove the cover from the old module
•
Remove the two cable quick connections from
the circuit board
•
Using pliers, squeeze the strain relief slots and
pull to remove the cable from the module
•
Retain the strain relief from the cable for use on
the Sentronic+ cable
© 2010 Emerson Climate Technologies
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•
Position the strain relief on the new cable at the
termination of the conduit
•
Feed the wires into the module through the hole
in the bottom of the case
•
Push the strain relief into position to lock it
•
Connect the two quick connects to the circuit
board. There is no polarity on the leads.
•
Install the module on the compressor and make
wiring and sensor connections per the general
instructions
Sentronic+ Terminal Strip
•
The Sentronic+ module terminal strip is designed
to accept a bare wire end instead of a spade
terminal
•
If a Sentronic+ module is being retrofitted to a
system with spade connections, the spade may
be clipped off and ¼” of the wire end stripped.
Or, one leg of the spade may be clipped off for
insertion into the terminal strip
Removing the cable from the old Sentronic module:
•
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Connecting the new cable to the old Sentronic module:
Removing the cable from the new Sentronic+ module:
•
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