3412E & C30 MARINE ENGINE Caterpillar

Negative Battery Bus Bar Connections

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All negative battery connections for electronic and electrical components in the electronic control system for marine engines must have a common ground that terminates at the Negative Battery Bus Bar. Improper grounding can cause unreliable and uncontrolled circuit paths. The engine may unexpectedly go to low idle, may fail to shut down, or may fail to change engine speed in response to the control system. Failure of the engine to respond to the control system could result in injury or death. When the electronic control system is installed, modified or repaired, all electronic circuits should be tested for correct installation and operation with the Electronic Control Module (ECM) and the electronic control system before the engine is started.

The alternator, the starting motor and all electrical systems must be grounded to the negative terminal of the battery. The alternator and the starting motor must also meet electrical isolation requirements for marine applications. If the engine has an alternator that is grounded to a engine component, a ground strap must connect the grounded component to the negative terminal of the battery. Also, the component must be electrically isolated from the engine.

Negative Battery Terminal Connection

A bus bar is recommended for use as a dedicated common connection to the negative battery terminal for all components that require a negative battery connection. Refer to "Power Supply Connections to The Starting System" in this manual for additional information. This bus bar should be directly connected to the negative battery terminal.

Use of the bus bar ensures that the ECM and all connected components have a common reference point. Connected components include switches, sensors and electronic display modules.

Starting System Schematic

Figure 16 - Starting System Schematic

Abbreviations for Figure 16 - "Starting System Schematic":

* ALT "Alternator"

* BAT, "Battery"

* -BAT, "Negative battery circuit

* -BATTERY BUS BAR "Negative Battery Bus Bar"

* +BATTERY BUS BAR "Positive Battery Bus Bar"

* +BATTERY (SWITCHED) "Switched Positive Battery circuit"

* +BATTERY (UNSWITCHED) "Unswitched Positive Battery circuit"

* CB "Circuit breaker"

* CISS "Customer installed start-stop switch"

* CPSS "Customer provided shutdown switch"

* DIAGNOSTIC "Diagnostic Lamp"

* ENGINE MOUNTED CONTROL PANEL "Engine mounted control panel"

* EMSS "Engine mounted start-stop switch"

* ES "Emergency Stop Switch"

* HM "Hour Meter"

* MAINT IND "Maintenance Indicator Lamp"

* MAINTENANCE CLEAR SWITCH "Maintenance Clear Switch"

* MTR "Connection for starting motor"

* RD "Red"

* REMOTE START "Remote start circuit"

* SHUTDOWN INPUT "Shutdown input circuit

* SM "Starting motor"

* SMMS "Starting motor mag switch"

* WARNING "Warning Indicator Lamp or alarm"

* YL "Yellow"

Power Supply Connections to the Starting System

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All negative battery connections for electronic and electrical components in the electronic control system for marine engines must have a common ground that terminates at the Negative Battery Bus Bar. Improper grounding can cause unreliable and uncontrolled circuit paths. The engine may unexpectedly go to low idle, may fail to shut down, or may fail to change speed in response to the control system. Failure of the engine to respond to the control system could result in injury or death. When the electronic control system is installed, modified or repaired, all electronic circuits should be tested for correct installation and operation with the Electronic Control Module (ECM) and the electronic control system before the engine is started.

Table 9: Allowable Wire Length to Connect Starting Motor to the Battery

The table above gives the size of wire and the maximum allowable length of the wire that is recommended to connect the battery to the starting motor.

The size of wire to the positive battery which supplies the power to electrical and electronic components must be of adequate size to carry the maximum current of the circuit.

The size of wire to the Negative Battery Bus Bar to which electrical and electronic components have a common connection must be of adequate size to carry the maximum current of the circuit.

The causes of intermittent shorts or power interruptions are often very difficult to identify. Proper wire connections for all electrical systems and connection to a common negative bus bar on the vessel are necessary for the correct performance and reliability of the engine.

The alternator, the starting motor, and all electrical systems must have a common with the negative battery terminal. The alternator and the starting motor must conform to electrical isolation requirements for marine applications.

If the alternator is grounded to an engine component, a ground strap must connect that component to the negative battery terminal. Also, that component must be electrically isolated from the engine.

Figure 17 - Battery Connections of Operator Stations for a Two Engine Arrangement

All negative battery connections on the components should be directly wired to the Negative Battery Bus Bar. Wire that is a minimum size of 12 AWG should be used to connect the operator stations to the Negative Battery Bus Bar that is located in the engine room.

Negative battery connections that conform to Figure 17 - "Battery Connections of Operator Stations for a Two Engine Arrangement" ensure that all components in the electrical system have the Negative Battery Bus Bar in the engine room as a common reference point. Reliable operation of the electrical system requires that all of the components in the system are correctly connected.

All wires for +Battery and -Battery Bus Bar to the P3 Customer Connector should have a wire size of 14 AWG.

Positive Battery Circuit for ECM Power

Use of dedicated circuit protection will reduce the possibility of system performance that is degraded due to voltage transients. Additional electrical loads should not be connected between the ECM and the circuit protection.

The ECM Switched Positive Battery terminal is connected to Customer Connector P3 pin 30.

To prevent engine shutdown in the event of a short circuit in the vessel wiring harness, the electronic control system must be powered on a dedicated protected circuit. The wire size should be 14 AWG. This connection should be made through the Switched Positive Battery circuit so that the electronic control system will be powered when the start switch in the ON/RUN position.

Do not use fuses for circuit protection. Circuit breakers should be used for circuit protection. Circuit breakers should be located with other circuit protection for the vessel in a dedicated panel that is centrally located.

If automatic reset circuit breakers are used, the location of the circuit breaker is critical. The trip point of these circuit breakers can be significantly reduced below the rated trip point of exposed to high temperatures which could cause intermittent shutdowns. Troubleshooting can easily fail to detect this problem which can result in incorrect replacement of components.

Switched Positive Battery Circuit

Figure 18 - Unswitched Positive Battery Connections

The installation requires an Unswitched Positive Battery circuit in addition to the Switched Positive Battery circuit that is described in "Positive Battery Circuit for Power to the ECM" section of this manual. The Unswitched +Battery connection is made to the Customer Connector P3 pins 1 and 5. The connection of the other end of the wire can be made to any Unswitched Positive Battery connection on the vessel.

The size of circuit breaker depends upon the number and the type of displays that are installed.

When the ECM is not energized, the current for this circuit is 6 milliampere with 24 VDC. The wire does not require a dedicated protected circuit. However, a dedicated protected circuit is recommended. The circuit protection should be rated at 5 amperes with a minimum of one ampere.

The ECM and the monitoring display must be powered from the same switch which provides a single power source. The same battery source must be used for all positive battery and negative battery connections.

Welding Guidelines for Engines with Electronic Controls

Proper welding procedures are necessary to avoid damage to electronic controls. The following procedures should be followed when welding on any engine or application that uses electronic controls:

* Stop the engine. Put the start switch in the OFF position.

* Disconnect the negative battery cable at the battery. If a battery disconnect switch is provided, put the switch in the OPEN position. Do not use electronic components such as the ECM, sensors, and ground straps as ground points for the welder. Do not use fuel system components for grounding the welder.

* Connect the clamp for the ground cable of the welder directly to the part or component area to be welded. Place this clamp as close as possible to the weld to reduce the possibility of damage by the welding current. Components which can be easily damaged include bearings, hydraulic components, and electrical components.

* Protect any wiring harness from welding debris and spatter.

* Use standard welding procedures to weld the materials.

Suppression Of Voltage Transients

The installation of transient suppression at the source of the transient and at the ECM is recommended. An environment standard for electrical components and systems that is equal to or more stringent than SAE J1455 should be followed.

The use of inductive devices such as relays and solenoids can result in the generation of voltage transients in electrical circuits. Voltage transients that are not suppressed can exceed the specifications of SAE J1455 which will degrade the performance of the electronic control system.

The OEM should specify relays and solenoids that have voltage transient suppression that is part of the component.

Figure 19 - Voltage Transient Suppression in a Relay Using a Diode

(A) Suppression of transient voltage in a relay with a low side driver or switch

(B) Suppression of transient voltage in a relay with a high side driver or switch.

Refer to Figure 19 - "Voltage Transient Suppression in a Relay Using a Diode" for examples of transient voltage suppression in a relay that uses a diode. Another method of transient voltage suppression is the use of a resistor with the correct resistance in parallel with a solenoid coil or relay coil.

Inductive devices such as relays or solenoids should be located to maximize the distance from components of the electronic control system. Wiring harnesses that are installed by the OEM should be located to maximize the distance from the wiring harness of the electronic control system to avoid the inductive coupling of noise transients.