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1 2010 Emerson Climate Technologies

Printed in the U.S.A.

AE8-1314 R1

Application Engineering

B U L L E T I N

AE8-1314 R1 February 2001Reformatted October 2010


B U L L E T I N

Introduction and Features

The Sentronic+ electronic oil pressure safety controluses a pressure sensor and an electronic moduleto precisely measure oil pump differential pressure.Common sources of leaks (bellows, capillary tubes,and pressure connections) are eliminated when usingthe Sentronic+.

Another advantage of Sentronic+ is a precise electronicclock for the two-minute time-out circuit. Traditionalmechanical controls use resistance heaters tomeasure the time-out in the event of low oil pressure.On 208V systems, low ambient temperatures orbrown-out type conditions cause the heater output tobe reduced, thus increasing the time-out period fromtwo minutes to three minutes or more when low oilpressure conditions exist. The electronic clock willalways provide a two-minute time-out.

The Copeland Sentronic+ module features a lightemitting diode (LED) to provide a visual indication ofthe oil pressure condition. To aid in trouble-shooting,the cover label has a summary of the LED faultindications.

Sentronic+ no longer requires the use of shieldedcables because of an electronic noise suppressionfeature.

All Copelametic compressors that have an external oilpump (see AE4-1166) require an Emerson-approvedoil pressure safety control. Failure to use an approvedoil pressure safety control will be considered misuseof the compressor and may void the warranty if thecompressor should fail due to lack of lubrication.

An oil pressure safety control must meet manyrequirements for Emerson approval. These

requirements include maintaining the pressure settingand time delay calibration within close limits over thewidest variation in expected operating conditions.Safety controls must pass a life test with a minimumof 200,000 cycles. Controls must be non-adjustableand must have a manual reset with a 120 secondnominal time delay at rated voltage, have a cut-outpressure setting of 7 to 9 PSID (Pounds per SquareInch Differential), and a cut-in pressure of 12-14PSID. In this case, PSID is the difference between thecrankcase pressure and oil pump outlet pressure.

Sentronic+

Electronic Oil Pressure Control

The module control base can accept either threaded orpush-in electrical conduit connections.

Basic Control Operation

The oil pressure sensor is mounted directly into theoil pump of the compressor. The Sentronic+ sensormeasures the oil pump differential pressure and hasan internal contact that opens due to low oil pressure,causing the Sentronic+ electronic control module tobegin the timing clock.

Should the oil pressure fall below 7 to 9 PSID for aperiod of two minutes, the Sentronic+ module will openthe normally closed control circuit, which shuts thecompressor off.

The Sentronic+ will also shut the compressor down ifthe oil pressure fluctuates between acceptable and lowoil pressure (indicated by an alternating red and greenLED) and records a history of low oil pressure for 60%or more of a running cycle. In addition, Sentronic+ hasa memory that will retain the oil pressure levels for upto one minute during a power loss.

A trip of the oil pressure safety switch is a warningthat the system has been without proper lubricationfor too long. Repeated trips of the oil pressure safetycontrol are a clear indication that something in thesystem requires immediate remedial action. On awell-designed system, there should be no trips ofthe oil pressure safety control, and repeated tripsshould never be accepted as a normal part of systemoperation.

Sentronic+ Control Module

In addition to the normally closed (N.C.) contactused for compressor shutdown, the Sentronic+ has anormally open (N.O.) contact which can be used in analarm circuit (See Figure 5).

The Single Pole Double Throw (S.P.D.T.) contact ofSentronic+ can be electrically isolated from the controlcircuit power supply and used to control a differentvoltage (See Figure 3).

Installation

All Copeland compressors with external oil pumpsshipped after September 1986 have a plug fitting in

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the oil pump for mounting the sensor. The externaloil pump is designed to accept either the Sentronic+sensor or a capillary tube for the traditional mechanicaloil pressure control.

Removing the cover on the module is accomplished bygently lifting two locking tabs on the lower corners ofthe cover and pulling the lower edge of the cover awayfrom the base. Refer to Figure 1.

Installation of the cover is accomplished by hookingthe top of the cover down on the three tabs on the topof the module base and swinging the cover back intoposition until the cover release tabs latch into place.Refer to Figure 2.

Installing the Sensor

1. Remove the plug fitting from the oil pump housing(new installations). Discard the copper washerfrom under the head of the plug fitting.

2. Install the new O ring into the groove around thesensor. Note: If applicable, replace the aged Oring with the new one supplied in the kit. Userefrigeration oil to pre-lubricate the O ring beforeinstallation. Use care not to cut the O ring.

3. Use the new copper washer. Do not reuse thecopper washer removed with the plug fitting.

4. Screw the sensor into the pump body. Torque thesensor to 60-65 Ft.-Lb.

Installing the Module

1. When using the bracket above the oil pump,use the supplied 10-32 pan head slotted screwswith washers. Alternatively, four holes have beenincorporated in the module base to provide theoption of remote mounting. Refer to Figure 7.The maximum screw length is .265 plus bracketthickness. Longer screws could damage thecircuit board.

2. Plug the cable from the module into the end ofthe sensor. Care should be taken to route thecable away from current carrying conductors.

Excessive hi-potting can cause damage to theSentronic+ module. If hi-potting is required, werecommend it be limited to a single time.

Figure 1 Figure 2

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Static electricity discharges from electrostatic paintingcan damage the Sentronic+ module. We recommendthat the module not be mounted until such painting iscompleted.

The module location and conduit lengths should bechosen to avoid bending of the conduit beyond itsnormal range offlexibility.

Remote Mounting

The Sentronic+ module sends a low voltage signalto determine whether the sensor circuit is opened orclosed. When the Sentronic+ module is mounted onthe compressor, the sensor will normally experienceno disturbances from nearby electrical sources.While the Sentronic+ is not particularly susceptible toElectromagnetic Field (EMF) interference, it is wise

to keep the cable away from other current carryingconductors.

Grounding

The Sentronic+ plus has been designed with a plasticcase, and does not require a ground connection. Aground screw is provided on the terminal strip for thoseinstallations utilizing a ground wire in the conduit.

Sentronic+ Specifications

Cut-Out 7-9 PSID

Cut-In 12-14PSID

Time Delay 120 seconds + 15 seconds

Sensor Torque 60-65 Ft.-Lb.Max Control 375 VA; 120V

Max Control 500 VA; 240V

Max Inrush 1600 VA; 120 V

Max Inrush 3000 VA; 240 V

Installing external timer

Caution:An electronic timer may be placed in serieswith the compressor contactor to force a delay beforeeach start and prevent possible short cycling. Thetimer must be located so it also prevents the Sentronic+from energizing during the timing period. SOMEINEXPENSIVE TIMERS MAY LEAK ENOUGHPOWER WHILE TIMING-OUT, TO ENERGIZETHE SENTRONIC+ EVEN THOUGH THERE MAYNOT BE ENOUGH LEAKAGE TO CLOSE THECOMPRESSOR CONTACTOR. THIS CAN CAUSE APREMATURE SENTRONIC+ TRIP.

If there is doubt, the circuit should be checkedbefore placing it in operation.

Standard Control Circuits

Both Figures 4A (Sentronic+) and 4B (previousSentronic) show typical wiring connections and the

similarity of Sentronic+

and Sentronic oil pressureswitches used on three-phase motor compressors.When the operating and limit controls are closed,the system is calling for the compressor to run. Theelectrical circuit for the Sentronic+ module consistsof a 240 V (120V) connection to the appropriateterminal and the jumper between 2 and M and thenormally closed (N.C.) contact between M and L.The compressor contactor circuit is completed bythe normally closed contact between M and L. Ifthe module trips the circuit due to low oil pressure,the N.C. contact between M and L opens therebyopening the circuit of the compressor contactor and

the module.

Once the Sentronic+ module has tripped, it must bemanually reset to restore operation.

Control with Alarm

The alarm circuit as seen in Figure 5 will be activatedwhen the Sentronic+ trips on low oil pressure. Thenormally open (N.O.) contactor between L and Awill be closed when the module trips thereby activatingthe alarm circuitry.

The Current Sensing Relay Used with CompressorInherent Motor Protectors:

A compressor may exhibit nuisance trips if it has aninherent protector and experiences motor overheating.The use of a current-sensing relay allows thecompressor to cycle on the internal inherent protectorwithout affecting the operation of the Sentronic+.

After an overload trip of a compressor with aninherent protector, the control circuit will still beclosed and the Sentronic energized although thecompressor motor is not operating. The two-minutetiming circuit will activate due to a lack of oil pressure,and after the 120-second time delay; the oil pressuresafety switch will trip. Even though the compressor

motor cools sufficiently for the internal inherentprotector to automatically reset, the compressor

cannot start until the oil pressure safety control ismanually reset.

This is normally not a problem since the compressor, ifproperly applied, will seldom if ever trip on the internalinherent protector. If it should happen to do so, thefact that a protector trip has occurred indicates thatthe system operation should be reviewed. However,

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on frozen food or other critical applications where aproduct loss may occur, if a compressor shutdownshould occur during the night or a weekend whenthe equipment is unattended, it may be desirable toprevent a possible nuisance trip by means of a currentsensing relay.

The current sensing Relay is mounted on the load sideof the contactor, senses by induction the full operatingcurrent of one phase of the motor, closes on a riseabove 14 amps, and opens if the load current fallsbelow 4 amps.

Figure 6 uses a current relay (C.S.). When the currentrelay is not energized by motor current, its NormallyOpen (N.O.) contact opens the circuit that powers theSentronic to avoid a nuisance trip.

NOTE: On some 550 volt motor-compressors, it maybe necessary to loop the current carrying wire so that itpasses through the current sensing relay twice in orderto increase the metered amperage to close the relaycontacts.

Using a Separate Control Voltage with theSentronic+ (Figure3)

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 andLL2. The separate voltage powers the compressorcontactor (CC) by means of a remote relay. When theremote relay is energized, requesting the compressorto run, its contact (RR), closes to deliver LL1 voltageto the operating and limit contacts. If the contacts in

the operating and limit circuit are closed, LL1 voltageenergizes the compressor contactor coil (CC). Whenthe compressor contactor closes, it provides thepower, through a control circuit transformer (XFMR),to energize the Sentronic+. If the Sentronic+ trips, itscontact (L to M) in the LL1-LL2 control circuitopens to de-energize the compressor contactor andstop the compressor. The Sentronic+ contact (L toA) closes to energize an Alarm Relay (AR).

Note that any A.C. voltage up to and including 240volts may be used. For line voltages greater than 240V, a step-down transformer (circuit transformer XFMRin Figure 3) must be used.

LED Interpretation

To aid in troubleshooting an oil pressure problem, the

Sentronic+ has an LED as a visual aid. This sectionexplains the information provided by the LED.

LED Green

Compressor has sufficient oil pressure.

LED Red

Compressor is experiencing insufficient oil pressure.

Red/Green LED Alternating

Compressor is experiencing erratic oil pressureindicating a possible system problem.

No Light

Control Circuit is not energized L or M for light circuit.

120V TERMINAL

TIMING

CIRCUIT

SENTRONIC

OPERATING

AND LIMIT

CONTROLS

SENSORAR = ALARM RELAY

RR = REMOTE RELAY

CC = COMPRESSOR CONTACTOR

XFMR = CONTROL TRANSFORMER

XFMR

MOTOR

L1 L2 L3

CC CC CC

RR

LL 1LL 2

CC

2

M

L

A AR

Figure 3

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Start Up Procedure

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Troubleshooting

Approximate oil pressure can be measured in thefield. Oil pumps are furnished with a Schrader valve

mounted on the oil pump discharge port. To measure oilpressure, subtract crankcase pressure from dischargeoil pressure.

Checking the Installed Sentronic+ Module

Shut off the compressor. Unplug the sensor. Read thecontrol voltage between the 240V (or 115V) terminaland the L (or 2 if separate control is used) terminal toverify power to the module.

Start the compressor with the sensor unplugged.Recheck to make sure the module voltage is stillpresent. After 120 seconds 15 seconds, the L-Mcontact should open and shut off the compressor.

With the module off due to low oil pressure, wait twominutes and press the reset button. Lack of power aftera reset may be due to an external time delay circuit.

Checking the Sensor

Unplug the sensor and, start the compressor. TheSentronic+ module LED should be red. Simultaneouslymeasure the oil pump differential pressure. Monitorthe two terminals at the back of the sensor withan ohmmeter or continuity measuring set. If thedifferential pressure is below the range of 7 to 9 PSID,the sensor circuit should be open (no continuity, infiniteresistance). If the pressure is above 12 to 14 PSID, thesensor circuit should be closed.

Measure the differential pressure by subtracting thecrankcase pressure from the oil pump outlet pressure.

USE EITHER 120V

OR 240V TERMINALSENTRONIC

TIMING

CIRCUIT

OPERATINGAND LIMIT

CONTROLS

A = ADDED ALARM LIGHT

A

CC

A

2

M

L

L1

L2

Figure 5

A

2

M

L

USE EITHER 120V

OR 240V TERMINAL

OPERATINGAND LIMITCONTROLS

MOTOR

CCCCCC

TIMING

CIRCUIT

SENTRONIC

CS = CURRENT SENSOR

CS

CC

A

CS (N.O.)

Figure 6

USE EITHER 120V

OR 240V TERMINAL

SENTRONIC

TIMING

CIRCUIT OPERATINGAND LIMITCONTROLS

MOTOR

SENSOR


CC

CCCCCC2

M

L

A

L1 L2 L3

Figure 4A

Sentronic+

230V OR

115V

SENTRONIC

TIMING

CIRCUIT OPERATINGAND LIMITCONTROLS

MOTOR

SENSOR


CC

CCCCCC

L

M

L1 L2 L3

Figure 4B

Previous Sentronic

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Interchangeability with Previous Sentronic Controls

The electronic two minute timing circuit operateswhenever voltage is applied to a Sentronic+, and it

has not tripped. The timing will be interrupted whenoil pressure rises above 12-14 PSID and closes theSentronic sensor. Should oil pressure not build upsufficiently within 120- seconds, the electronic delaywill time out, open its L-M contact, break the controlcircuit, and de-energize the compressor contactor tostop compressor operation.

While the compressor is running, if the compressornet oil pressure falls below the cut-out setting of thesensor while operating, and does not re-establishsufficient pressure within an acceptable time, thetime delay circuit will open the L-M contacts, stoppingcompressor operation. Once the oil pressure switch

has tripped, it must be manually reset to restore thesystem to operation.

IMPORTANT: If a power interruption occurs after an oilpressure safety trip, wait two minutes before resettingafter power is restored.

Electrical bench checkout procedure

This instruction sheet describes how the Sentronic+may be easily bench-checked using only a voltmeterand a 120VAC electrical extension cord.

CAUTION!

Damage to the Sentronic+ module may result ifthe M terminal of the Sentronic+ is connected toground or directly to a voltage line!

This test is conducted with 120VAC. A shock willresult if the Sentronic+ terminals are touchedwhen the Sentronic module is energized.

Use care whenever working with any voltage!Make sure your electrical outlet is grounded, theelectrical extension cord used has a ground wire,and the ground wire is connected to the groundingscrew of the Sentronic+ .

1. Apply 120VAC power to the Sentronic+ moduleterminals marked 120 and L. The Sentronicshould have a jumper in place between terminalsM and 2.

2. Wait two minutes, then push the Sentronic+ resetbutton to reset the module and start the timingcircuit.

3. With a voltmeter, measure line voltage (120VAC)

between the M terminal and the 120 terminal.It should be the same as the electrical outletvoltage - about 120VAC.

4. Since there is no connection made to thepressure sensor, the module sees this as a no-oil pressure condition. After two minutes (plus orminus 15 seconds - dependent on 50 or 60 cyclefrequency) the Sentronic internal timer will time-out. The module will trip; the circuit betweenL and M will open, and it will no longer passcurrent to the load.

5. With the voltmeter connected to terminals Mand 120, the voltage should now read zerovolts because the circuit between L and M hasbeen opened through the action of the electroniccircuit.

6. Reset the Sentronic+, then remove voltage fromterminals 120 and L. With a small piece ofwire, jumper the female sensor connections atthe end of the black sensor cord attached to themodule. Reapply power to terminals 120 andL and wait two minutes. The module should nottime-out after two minutes because jumperingthe sensor connections makes the timing circuitsee good oil pressure. The jumper imitates theaction of a small pressure switch located in thesensor. This switch opens on low oil pressure andcloses on good oil pressure.

7. Measure between the 120 terminal and the Mterminal with the voltmeter. The meter shouldread full line voltage showing that the circuit hasnot opened.

8. To check if the module will operate on 208/240volts as well as on 120 volts, change the scaleof the voltmeter (if necessary), to read up to250VAC. Without removing power, measure thevoltage between the M terminal and the 240terminal. You should read nearly twice the voltageas that read between the M terminal and the120 terminal. This is because Sentronic+ hasa small control transformer connected so that

it can accept either 120V or 208/240V. Its self-transforming action actually enables it to step upits own voltage. By making this voltage check, thetransformer is being checked.

9. If the module successfully passes the above testsequence it is fully functional. If the module failsany of the above steps, it is faulty and should bereplaced.

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Remove the two cable quick connections fromthe circuit board

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:

Remove the cover from the Sentronic+ module

Pull the 2 cable quick connects from the circuitboard (these are labeled Org and Red)

Remove the wires from the strain relief (note therouting of the wires for future reference) and liftthe wires out

Remove the wire cable from the module bytwisting the conduit counterclockwise and gentlypulling

Connecting the old cable to the Sentronic+ module:

Trim approximately 2 of cable sheathing fromthe module end of the old cable, taking care notto nick the wire insulation

Feed the wires into the module through the holein the bottom of the case

Leaving enough lead length to reach the quickconnects, push the wires into the strain relief.

Connect the 2 quick-connects to the ORGand RED spades. (Note: the connections maybe 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 generalinstructions.

Interchangeability of Sentronic+ and Sentronicmodules and sensors

The Sentronic+ oil pressure control uses both a

new module and a new sensor. The sensors andmodule can be made compatible with older generationcomponents if the following steps are taken:

To use a Sentronic+ module with an older Sentronicsensor, the older Sentronic sensor cable must be wiredto the new Sentronic+ module.

To use an older Sentronic module with a Sentronic+sensor, the Sentronic+ cable must be wired to theSentronic module.

There is an older generation Sentronic module whichis fully compatible with the Sentronic+ sensor. It is

supplied with the new (Sentronic+) cable which isgray for identification purposes, see illustration below.

New Sentronic+ Old Sentronic

Connecting the Sentronic+ module to an olderSentronic sensor

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

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Connecting the older Sentronic module toSentronic+ sensor

Removing the cable from the new Sentronic+ module:

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 circuitboard (these are labeled Org and Red)

Remove the wires from the strain relief by liftingthe wires out

Remove the wire cable from the module bytwisting the conduit counterclockwise and gentlypulling

Removing the cable from the old Sentronic module:

Remove the cover from the old module

Remove the two cable quick connections fromthe circuit board

Using pliers, squeeze the strain relief slots andpull to remove the cable from the module

Retain the strain relief from the cable for use onthe Sentronic+ cable

Connecting the new cable to the old Sentronic module:

Position the strain relief on the new cable at thetermination of the conduit

Feed the wires into the module through the holein the bottom of the case

Push the strain relief into position to lock it

Connect the two quick connects to the circuitboard. There is no polarity on the leads.

Install the module on the compressor and makewiring and sensor connections per the generalinstructions

Sentronic+ Terminal Strip

The Sentronic+ module terminal strip is designedto accept a bare wire end instead of a spadeterminal

If a Sentronic+ module is being retrofitted to asystem with spade connections, the spade maybe clipped off and of the wire end stripped.Or, one leg of the spade may be clipped off forinsertion into the terminal strip

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