Introduction

The Energize To Run (ETR) electric protection system offers full engine system protection (OP, WT, OS).

The ETR type protection system requires that the gas shutoff valve (GSOV) must first be activated (and must remain activated) before fuel is allowed to the engine cylinders. After the engine starts to run, a problem with any of the engine systems that are monitored will cause the gas shutoff valve to be deactivated. This will immediately stop fuel to the cylinders and cause engine shutdown.

The full protection system arrangement monitors the engine from starting through 118% of rated speed.

Component Description

Electronic Speed Switch (ESS)

7W2743 Electronic Speed Switch (ESS)
(1) Verify button. (2) Reset button. (3) "LED" overspeed light. (4) Seal screw plug (overspeed). (5) Seal screw plug (crank terminate). (6) Seal screw plug (oil step).

The Electronic Speed Switch (ESS) is designed with controls built into a single unit to monitor several functions at the same time. The functions that the ESS monitors are:

Engine Overspeed (OS)

This is an adjustable engine speed setting (normally 118% of rated speed) that prevents engine from running at a speed that could cause damage to the engine. This condition will cause a switch to close that shuts off the fuel to the engine.

Crank Termination (CT)

This is an adjustable engine speed setting that signals the starter motor that the engine is firing and cranking must be terminated. When the speed setting is reached, a switch will open to stop current flow to the starter motor circuit. The starter motor pinion gear will now disengage from the engine flywheel ring gear.

Oil Step Latch

This feature of the ESS is not adjustable. After terminal ESS-17 has been energized by loss of engine oil pressure, the oil step switch (OPSS) contacts are now held in the closed position. This will maintain OPSS in a closed position until 2 seconds after the engine has completely stopped. This action will prevent the shutoff from resetting below oil step speed.

Engine Oil Step Pressure

This is an adjustable engine speed setting that gives protection to the engine from a failure caused by too little oil pressure for a specified speed range. To maintain desired protection through the complete speed range of operation, two different oil pressure switches are used. One with a high pressure rating (OPS2), and one with a low pressure rating (OPS1).

Once the oil step pressure speed setting is made, an engine that runs above this speed setting must maintain an oil pressure that is more than the higher oil pressure switch (OPS2) rating if oil step latch is used.

An engine that runs below this speed setting must maintain an oil pressure that is more than the lower oil pressure switch (OPS1) rating. If either condition is not correct, a switch will close to activate an alarm or cause the fuel to be stopped to the engine.

Magnetic Pickup (MPU)

Magnetic Pickup
(1) Clearance dimension. (2) Magnetic pickup. (3) Wires. (4) Locknut. (5) Gear tooth. (6) Housing.

The magnetic pickup is a single pole, permanent magnet generator made of wire coils around a permanent magnet pole piece. As the teeth of the flywheel ring gear go through the magnetic lines of force around the pickup, an AC voltage is made. A positive voltage is made when each tooth goes by the pole piece. Each time the space between the teeth goes by the pole piece, a negative voltage is made. Engine speed is then determined by the frequency of these signals.

Oil Pressure Switch (OPS)

Oil Pressure Switch

The oil pressure switch uses a spring loaded piston to activate a micro switch for a specific pressure rating. This type of switch has better accuracy over the operating temperature range and uses a much higher electrical contact rating to improve reliability.

Water Temperature Contactor Switch (WTS)

Water Temperature Contactor Switch

The contactor switch for water temperature is installed in the regulator housing. No adjustment to the temperature range of the contactor can be made. The element feels the temperature of the coolant and then operates the micro switch in the contactor when the coolant temperature is too high. The element must be in contact with the coolant to operate correctly. If the reason for the engine being too hot is caused by low coolant level or no coolant, the contactor switch will not operate.

The contactor switch is normally connected to the electric shutoff system to stop the engine. The switch can also be connected to an alarm system. When the temperature of the coolant lowers again to the operating range, the contactor switch opens automatically.

Air Inlet Temperature Switch

Air Inlet Temperature Switch (AITS)

The contactor switch for air inlet temperature is installed in the distribution channel. No adjustment to the temperature range of the contactor can be made. The element feels the temperature of the inlet air and then operates the micro switch in the contactor when the inlet air temperature is too high. The element must be in contact with the inlet air to operate correctly.

The contactor switch is normally connected to the electric shutoff system to stop the engine. The switch can also be connected to an alarm system. When the temperature of the inlet air lowers again to the operating range, the contactor switch opens automatically.

Slave Relay (SR)

This is a standard type relay that, when energized, has contacts that open across one circuit and close across another circuit. The circuits are wired so that power to the solenoids or the 2301 or 2301A Governor is controlled by the slave relays.

Circuit Breaker

Circuit Breaker Schematic
(1) Reset button. (2) Disc in open position. (3) Contacts. (4) Disc. (5) Battery circuit terminals.

The circuit breaker is a switch that opens the battery circuit if the current in the electrical system goes higher than the rating of the circuit breaker.

A heat activated metal disc with a contact point completes the electric circuit through the circuit breaker. If the current in the electrical system gets too high, it causes the metal disc to get hot. This heat causes a distortion of metal disc which opens the contacts and breaks the circuit. A circuit breaker that is open can be reset after it cools. Push the reset button to close the contacts and reset the circuit breaker.

Solenoid

A solenoid is a magnetic switch that causes low current to close a high current circuit.

The solenoid has an electromagnet with a core which moves. There are contacts on the end of the core. The contacts are held in the open position by a spring that pushes the core from the center of the coil. Low current will energize the coil and will make a magnetic field. The magnetic field pulls the core to the center of the coil and the contacts close.

Gas Shutoff Valve (GSOV)

This gas shutoff valve is located upstream of the fuel pressure regulator of the engine. When the solenoid (GSOV) is energized, high pressure gaseous fuel is admitted to the engine. This valve must remain activated or the fuel will be shutoff to the engine.

Protection System Battery Drain

There are two components used in the electric protection system that continue to draw small amounts of current from the battery when the engine is not running. These components are the electronic speed switch (ESS) and the charging alternator.

For a system that uses only one of these components, an engine can remain shut down for months without discharging the battery enough to prevent starting. Systems that use both of the above components may remain idle for a month or more without excessive battery drain. Cold weather decreases battery efficiency and will reduce these time periods even more.

In most applications, the engine is started weekly or a battery charger is used to keep the battery at full charge, so few problems have been noted. For those applications where the engine is not used for extended periods (such as rental fleets), the suggestions that follow can be used to prevent battery discharge.

If the engine will not be operated for several weeks (without a battery charger), disconnect the battery cable from the negative (-) side of the battery. If it is expected that this condition will happen frequently, the 7N0718 Battery Disconnect Switch can be installed for convenience. This switch should be installed between the negative terminal of the battery and the negative terminal of the starter motor.

A suitable bracket should be fabricated to mount the switch close to either the battery or the starter motor (the switch can be mounted inside the power distribution box on generator set engines). In all applications, the 7N0718 Battery Disconnect Switch should be mounted within 30° of vertical.

Component Locations On Engine

Water Temperature Contactor Switch

Water Temperature Contactor Switch
(1) Contactor switch. (2) Regulator housing.

Gas Shutoff Valve (GSOV)

Gas Shutoff Valve (GSOV)
(1) Regulator. (2) Gas Shutoff Valve (GSOV).

Magnetic Pickup and Magneto

Magnetic Pickup and Magneto
(1) Magnetic Pickup. (2) Magneto.

Junction Box

Junction Box
(1) Junction Box. (2) Emergency stop switch (ES). (3) Circuit breakers. (4) Oil pressure switches (OPS1 and OPS2) (located on the back of the junction box).

Junction Box (SI-ETR)

Junction Box (SI-ETR) - Oil Pressure, Water Temperature, Overspeed (Shown With Door Open)
(1) Terminal strips (TS). (2) Wiring harness. (3) Electronic speed switch (ESS). (4) Junction box. (5) Emergency stop switch (ES). (6) Identification foil. (7) Jumpers. (8) Diodes. (9) Slave relays (SR1, SR2 & SR3). (10) Base. (11) Circuit breakers (CB).

Junction Box (SI-ETR) (as seen from rear)
(12) Oil pressure switches (OPS1 and OPS2).

Introduction

This ETR junction box circuit (full independent system) is a complete system. It is designed to monitor engine overspeed, oil pressure, coolant temperature and starter motor overcrank.

The junction box components include an electronic speed switch (ESS), a gas shutoff valve (GSOV), three slave relays (SR1, SR2 and SR3), an oil pressure switches (OPS1 and OPS2), and a water temperature switch (WTS).

The ETR system requires that slave relay (SR1) and gas shutoff valve (GSOV) must remain energized in order for the engine to run.

Electrical Schematics And Wiring Diagrams

The point-to-point wiring diagrams for both the complete engine protective system including timing control and the junction box are located in the Wiring Diagrams Section of this module.

Connections For Temporary Start-up

If an engine with this system needs to be started temporarily before installation in plant, use the wiring suggestions that follow:

1. Connect a jumper wire across J box terminal strip terminals TS-4 and TS-5, and across terminals TS-26 and TS-14.

2. Connect a START switch across J box terminal strip terminals TS-21 and TS-26.

3. To stop engine remove jumper TS-4 to TS-5 or use ESPB.

All fault circuits are now operational as they would be if the engine was in its final installation. The only difference is that the engine must have enough oil pressure to open OPS1 at the time the engine just starts to run. If not, this circuit will cause immediate shutdown of the engine.

Circuit Operation: No Faults

Engine Stopped

With the engine stopped, power is always available across terminals 5 and 6 (line 58) of electronic speed switch (ESS). At this time all switches are in their normally open or normally closed positions.

Engine Start-up

Start-Stop Switch (SSS)

NOTE: The start-stop switch (SSS) is supplied by the customer.

When the start-stop switch (SSS) is moved to the START position it closes the circuit to the starter motor. The starter motor magnetic switch (SMMS) (line 9) is now energized to close its contact (line 3) to energize the pinion solenoid (PS) (line 3). Solenoid (PS) now closes its contact (line 2) to energize the starter motor (SM).

Also when the SSS is in the START position, the circuit is closed and the current now can flow through diode (D3) (line 18), through normally closed water temperature switch (WTS), to energize slave relay (SR1) (line 36). Relay SR1 now closes its normally open contacts SR1-1 and SR1-3 (line 46) to energize gas shutoff valve (GSOV). Fuel is now provided to start the engine.

When the engine starts to run and the crank termination speed is reached, the crank termination (CT) switch [in the electronic speed switch (ESS)] opens its contacts across terminals ESS-11 and ESS-12 (line 17) and closes across terminals ESS-11 and ESS-10. When ESS (CT) contacts open across terminals ESS-11 and ESS-12, current flow is stopped to the starter motor circuit and the starter motor will stop (even if SSS is held in the START position).

At the same time, ESS (CT) closes across contacts ESS-11 and ESS-10 (line 17) and the current now takes a path through diode (D2) and through overspeed switch (OSS) contacts ESS-8 and ESS-9 (line 29), then continues on through WTS (line 18) to the SSS. If the SSS is still held in the START position, current will go across the contacts of the SSS and on directly to SR1 (line 36) to keep it energized.

NOTE: To prevent premature engine shutdown due to oil pressure fault, hold the SSS in the START position until oil pressure is seen on the oil pressure gauge.

When the SSS is released from the START position, the switch automatically moves to the RUN position. Current now flows across the closed oil pressure switch (OPS1) contacts OPS1-1 and OPS1-2 (line 13) and, if used, across optional oil pressure step switch ESS (OPSS) contacts ESS-14 and ESS-15 and on directly to SR1 (line 36) to keep it energized.

If OPS1 has not closed across contacts OPS1-1 and OPS1-2 by the time the SSS is released to the RUN position, SR1 will be de-energized and circuit will automatically cause immediate engine shutdown.

Engine Normal Stop

The operator stops the engine by moving the start-stop switch (SSS) from the RUN position to the STOP position.

When moved to the STOP position, the SSS contacts open and the normal circuit for current flow through oil pressure switch (OPS1) and oil pressure step switch ESS (OPSS) (line 13) to slave relay (SR1) has now been interrupted, and SR1 is de-energized. Relay SR1 now opens its contacts across SR1-1 and SR1-3 (line 46) which de-energizes gas shutoff valve (GSOV). This shuts the fuel off to the engine.

The circuit of this system is wired so that engine can be restarted again immediately.

Emergency Stop Push button (ESPB)

The emergency stop push button (ESPB) is a red, mushroom shaped button that is located on the front of the junction box door. The ESPB will shut the engine down, and will also prevent the engine from being restarted (because button latches in this position when pushed in).

When ESPB is pushed in, an open circuit is made across contacts ESPB-1A and ESPB-2A (line 9) and across contacts ESPB-1B and ESPB-2B (line 18). The open circuit at line 9 stops any possible current flow to the starter motor circuit, and the open circuit at line 18 stops any possible current flow to slave relay (SR1). With SR1 de-energized, the contacts will open across SR1-1 and SR1-3 (line 46) to de-energize the gas shutoff valve (GSOV) and stop fuel to the engine.

At the same time, a closed circuit is made across contacts ESPB-3A and ESPB-4A (line 33) and across contacts ESPB-3B and ESPB-4B (line 34). The circuit across contacts ESPB-3A and ESPB-4A will now energize slave relay (SR2), and relay contacts SR2 (line 51) will energize and ground the magneto. This will cut ignition to the engine.

With engine stopped, crank terminals switch ESS (CT) (line 17) will have opened across contacts ESS-11 and ESS-12 to de-energize SR2 (line 33). Relay SR2 contacts (line 51) will now return to their normally open position and allow the magneto to fire.

Show/hide table

To prevent personal injury during repair or maintenance operations, disconnect the batteries to prevent the engine from starting.

Before starting the engine again, do the procedure that follows:

1. Correct any faults that may have been the cause of the emergency shutdown.

2. Make sure red (ESPB) has been reset (button out) on the engine junction box. To reset, turn the button in the direction shown on the button face.

3. Move and hold SSS in the START position to restart the engine.

Fault Circuit Operation

Oil Pressure Fault (OPS1)

If the engine is running with normal oil pressure, oil pressure switch (OPS1) (line 13) would be closed across contacts OPS1-1 and OPS1-2. Under these conditions, current would follow a path through closed crank termination switch ESS (CT) (line 17), through open overspeed switch ESS (OS) (line 29), through closed water temperature switch (WTS) (line 18), through the start-stop switch (SSS) [in the RUN position], and through closed OPS1 switch (line 13) to energize slave relay (SR1). If optional oil pressure step switch ESS (OPSS) (line 13) is used (engine would be running at some speed below step speed setting), current would also flow through open ESS (OPSS).

If engine now loses oil pressure, OPS1 switch will open across contacts OPS1-1 and OPS1-2 (line 13) and close across OPS1-1 and OPS1-3. This makes an open circuit to de-energize SR1, and relay contacts across SR1-1 and SR1-3 (line 46) will open to de-energize the gas shutoff valve (GSOV). This stops fuel to the engine and causes engine shutdown.

At the same time, when the switch closes across OPS1-1 and OPS1-3 (line 13), the oil step latch of electronic speed switch (ESS-17) is now energized. The oil step latch is a feature that will now hold ESS (CT) switch (line 17) in a closed position across ESS-11 and ESS-10 until two seconds after engine rotation has stopped. This prevents possible damage to starter motor pinion or flywheel ring gear due to a restart attempt before engine has completely stopped.

After ESS (CT) opens across contacts ESS-11 and ESS-12 and closes across ESS-11 and ESS-10, engine restart can be attempted immediately.

Oil Pressure Fault (OPS2) (Optional)

This condition can exist if there is a fault in the optional high pressure side of the oil pressure circuit (engine must be running at a speed above the optional step speed setting). With the engine running at this higher speed, the current path would be the same as noted in the previous story, OIL PRESSURE FAULT (OPS1) except that oil pressure step switch ESS (OPSS) would be closed across contacts ESS-14 and ESS-13 (line 13) and oil pressure switch (OPS2) would be closed across contacts OPS2-1 and OPS2-2. The current would now flow through these switches, through diode (D4) and on to energize slave relay (SR1).

When engine oil pressure drops below the higher pressure rating of OPS2, the switch will open across contacts OPS2-1 and OPS2-2 (line 13) and close across contacts OPS2-1 and OPS2-3. This open circuit now de-energizes SR1 (line 36) and relay will now open across contacts SR1-1 and SR1-3 (line 46) to de-energize the gas shutoff valve (GSOV). This stops fuel to the engine and causes engine shutdown.

At the same time, when switch closes across OPS2-1 and OPS2-3 (line 13), the oil step latch of electronic speed switch (ESS-17) is now energized. The oil step latch is a feature that will now hold ESS(CT) switch (line 17) in a closed position across ESS-11 and ESS-10 until two seconds after engine rotation has completely stopped. This prevents possible damage to starter motor pinion or flywheel ring gear due to a restart attempt before engine has completely stopped.

After ESS (CT) opens across contacts ESS-11 and ESS-12 and closes across ESS-11 and ESS-10, engine restart can be attempted immediately.

Show/hide table

To prevent personal injury during repair or maintenance operations, disconnect the batteries to prevent the engine from starting.

Engine Overspeed

When engine speed increases above the overspeed setting (118% of rated speed) of the electronic speed switch (ESS), the overspeed switch ESS (OSS) will close across terminals ESS-8 and ESS-7 (line 29). This immediately energizes slave relay (SR2), and the normally open relay contacts across SR2-1 and SR2-3 (line 51) now close to energize and ground the magneto. This will cut ignition to the engine.

At the same time, ESS (CT) switch opens across contacts ESS-11 and ESS-10 (line 17). This opens the circuit to now de-energize slave relay (SR1). Relay SR1 now opens across contacts SR1-1 and SR1-3 (line 46) to de-energize the gas shutoff valve (GSOV) and stop fuel to the engine.

Show/hide table

To prevent personal injury during repair or maintenance operations, disconnect the batteries to prevent the engine from starting.

A reset button on the ESS must be manually pushed to open the overspeed switch ESS (OSS) again before the engine can be restarted.

Water Temperature Fault (WTS)

The current flow for the circuit discussed here is for an engine that is running at any speed with coolant temperature hot enough to close the normally open water temperature contactor switch (WTS). When WTS (line 18) closes, this opens the circuit to slave relay (SR1) (line 36). With SR1 de-energized, the relay will now open across contacts SR1-1 and SR1-3 (line 46) to de-energize the gas shutoff valve (GSOV). This will shut the fuel off to the engine. The starter motor circuit can now be engaged, but engine cannot be restarted (no fuel available) until the coolant temperature cools down enough to open WTS again. Then slave relay (SR1) and the gas shutoff valve (GSOV) can be energized again for engine restart.

Air Inlet Temperature Fault (AITS) (Standard Engine)

When the inlet air temperature increases above the temperature switch point, the switch will open across AITS-2 and AITS-3 and will close across AITS-2 and AITS-1. This open circuit now de-energizes SR1 (line 36) and the relay will now open across contacts SR1-1 and SR1-3 (line 46) and de-energize the gas shutoff valve (GSOV). This stops fuel to the engine and causes the engine to shutdown. The starter motor can now be engaged, but the engine cannot be restarted (no fuel available) until the inlet air temperature drops below the switch point to open AITS again. Then slave relay (SR1) and the gas shutoff valve (GSOV) can be energized again for engine restart.

SI Timing Control Fault (Low Emissions Engine)

When the engine is running and experiences heavy detonation or detonation which cannot be corrected by the timing control retarding the timing, the timing control will produce a fault signal. This fault signal will energize SR3. The switch opens across SR3-1 and SR3-2 (line 36). When SR3-1 and SR3-2 opens, current can no longer flow to SR1. This open circuit will now de-energize SR1 and the relay will now open across contacts SR1-1 and SR1-3 (line 46) to de-energize the gas shutoff valve (GSOV). This stops fuel to the engine and causes engine shutdown.

Electric Governor Control System

When the 2301 or 2301A Electric Governor Control (EGC) is used, all systems of the electronic speed switch (ESS) are activated in the same way as discussed with the non-electric governors.

With this circuit, current normally flows from TS-28 and TS-31 (lines 46 and 47) through pre-regulator (PR) at line 55 or fuse (F4) into EGC. When engine flywheel is in rotation, current also flows through electric governor actuator (EGA) at line 58. When a fault in the system causes current to de-energize slave relay (SR1), the switch closes across contacts SR1-1 and SR1-2 (line 48) and opens across contacts SR1-1 and SR1-3 (line 46).

When the circuit is opened across contacts SR1-1 and SR1-3, current can no longer flow to the EGC. This also stops current to the EGA, and the mechanical spring load in the EGA system will now move the fuel control rod to shut the fuel off to the engine.

NOTE: Except for the above differences, all fault circuits for the protective system are the same for the 2301 or 2301A Electric Governor as for the non-electric governors.

Wiring Diagrams

Introduction

The section that follows contains point-to-point junction box wiring diagrams and also junction box wiring harness diagrams for SI Engines. These diagrams can be helpful for the user who is not familiar with the electrical schematic-type format, or who is interested in the component position layout for replacement purposes.

Abbreviations, Notes, And Symbols

Junction Box Wiring (SI-ETR)

Engine Control System DC Schematic

Supplemental Wiring Diagrams

Optional Dual Starting Motors

Optional Prelube Pump