Introduction

The electric protection system for spark ignited engines is available in two different junction (J) box arrangements. The J box arrangements are used on either an Energize To Shutoff (ETS) or Energize To Run (ETR) system depending on the type of gas shutoff valve used and how it is wired to the J box terminal strip. Both J box arrangements offer full engine system protection (OP, WT, OS). One of the J box arrangements is completely independent as purchased, while the other arrangement needs an outside switchgear to make it functional.

In these J box arrangements the time delay relay must arm the system before it becomes effective. Once the system is armed, a problem with any of the engine systems that are monitored will cause the gas shutoff valve to be activated. This will immediately stop fuel to the engine and cause engine shutdown. At the same time, the magneto is connected to ground to stop current flow to the spark plugs.

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

Component Description

Electronic Speed Switch (ESS)

7W2743 or 4W2218 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. Two different ESS switches are used, but the only difference is mounting hole location. The functions that the ESS monitors are:

Engine Overspeed (OS)

This is an adjustable engine speed setting (normally 118% of rated speed) that prevents the engine from running at a speed that could cause damage. This condition will cause a switch to close that shuts off the fuel to the engine and connects the magneto to ground to stop current flow to the spark plugs.

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 closed position until 2 seconds after the engine has completepy stopped. This action will prevent the shutoff from resetting below oil step speed.

Engine Step Oil 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 step oil 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

This contactor switch is mounted into the coolant system and is wired to the protection circuit. It has an element that feels the temperature of the coolant (it must be in contact with the coolant). When the engine coolant temperature becomes too high, the switch closes to activate an alarm or cause the fuel to be shut off to the engine.

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 gas shutoff solenoids and the 2301 Governor is controlled by the slave relays.

Start Aid Switch (SAS)

The optional start aid switch (SAS) is located on the front of the junction box door. It is a spring return switch which has to be held in the ON position. When the SAS is moved to the ON position, the start aid solenoid valve (SASV) energizes to meter a specific amount of ether into a holding chamber. When the SAS is released, the SASV releases the ether to the engine.

The start aid circuit can be de-activated either of two ways:

1. Electronic speed switch (ESS) crank termination (CT) opens its contact at a preset engine speed (stops current to this circuit).

2. Temperature of engine becomes high enough to open the start aid temperature switch (SATS).

Circuit Breaker

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 the 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.

CIRCUIT BREAKER SCHEMATIC
1. Reset button. 2. Disc in open position. 3. Contacts. 4. Disc. 5. Battery circuit terminals.

Time Delay Relay (TD)

This relay is a special ON/OFF switch with two controls. When energized, one control will make the relay activate immediately and the other control will activate after a delay of 9 seconds (with continuous signal available). The time delay relay is used to arm the protection system and is energized by the crank terminate circuit, the oil pressure circuit, or both circuits at the same time.

The time delay relay has a 70 second OFF delay after signal is removed from both input terminals TD-1 and TD-2.

ON/OFF TIME DELAY RELAY

Junction Box (OP, WT, OS)

JUNCTION BOX - 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. Base. 8. Slave relays (SR1 & SR2). 9. Jumpers. 10. Diodes. 11. Start-stop switch (SSS). 12. Time delay relay (TD). 13. Grommets. 14. Circuit breakers (CB).

Introduction

This junction box circuit (full independent system) with a start-stop switch is a complete system and can be used with a switch gear that does not contain a cranking panel. It is designed to monitor engine overspeed, oil pressure, coolant temperature and starter motor overspeed.

The junction box components include an electronic speed switch (ESS), a time delay relay (TD), two slave relays (SR1 activates the gas shutoff valve and SR2 connects the magneto to ground), an oil pressure switch (OPS) or switches (OPS1 and OPS2), and a water temperature switch (WTS).

The system requires that relays SR1 and SR2 remain de-energized in order for the engine to run. Also, the gas shutoff valve can either be energized to run (ETR) or energized to shutoff (ETS).

Electrical Schematics And Wiring Diagrams

To follow the circuit operations and find component locations (line reference numbers), see Electrical Schematic Form No. SENR3468 in the separate Electrical Schematic Section of this Service Manual. This schematic includes both the IEC (International Electro-Technical Commission) and the JIC (Joint Industrial Council) symbols.

The point-to-point wiring diagrams for the junction box are located in the Wiring Diagrams Section of this module.

Circuit Operation: No Faults

Engine Stopped

With the engine stopped, power is always available across terminals 3 and 4 (line 12) of time delay relay (TD) and across terminals 5 and 6 (line 53) of electronic speed switch (ESS). At this time all switches are in their normally open or normally closed positions.

Engine Start-up

NOTE: On the front of the junction box door there is a start-stop toggle switch that is spring loaded. It will automatically return to the center (RUN) position when released from the START position.

When the Start-Stop Switch (SSS) is moved to the START position (up), the circuit to the starter motor is closed across terminals SSS-2 and SSS-1 (line 9). The starter motor magnetic switch (SMMS) (line 9) now energizes to close its contact (line 3) to energize the pinion solenoid (PS) (line 3). Solenoid PS then closes its contact (line 2) to energize the starter motor (SM). When the engine starts to run and the crank termination speed setting is reached, electronic speed switch (ESS) crank terminate switch (CT) opens its contacts across terminals ESS-11 and ESS-12 (line 9) and closes its contacts across terminals ESS-10 and ESS-11 (line 13).

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 (SM) will now stop. At the same time, ESS(CT) contacts close across terminals ESS-11 and ESS-10 to energize Control 2 (terminal TD-2) of the time delay relay (TD) (line 13). After 9 seconds, TD then closes contacts across terminals TD-6 and TD-7 (line 36) to arm the shutoff circuit to slave relay (SR1) (line 36) and SR2 (line 33).

Control 1 (terminal TD-1) of the time delay will also be energized as soon as engine oil pressure increases enough to make oil pressure switch (OPS1) (line 15) contacts open across terminals OPS1-1 and OPS1-3, and close across terminals OPS1-1 and OPS1-2. Energizing TD-1 will immediately (no delay) close contacts across terminals TD-6 and TD-7 (line 36) to arm the shutoff circuit to SR1 and SR2.

NOTE: If engine oil pressure (after the 9 second time limit) is still too low to open oil pressure switch (OPS1) contacts across terminals OPS1-1 and OPS1-3 (line 15), slave relay (SR1) (line 36) and (SR2) (line 33) will be energized and engine shutdown will occur. See FAULT CIRCUIT OPERATION for the complete circuit description with these conditions.

Engine Running At Rated Speed

With no engine problems and engine running at rated speed, or at some speed above the optional oil step speed setting, the oil pressure step switch ESS(OPSS) at line 17 is now closed across terminals ESS-14 and ESS-13. At the same time, oil pressure switch (OPS2) (line 17) is now open across contacts OPS2-1 and OPS2-3, so there is still no current flow to energize slave relay (SR1) at line 36. The engine will continue to run with these conditions.

OPS2 (line 17) will not open across contacts OPS2-1 and OPS2-3 until oil pressure increases to the OPS2 switch rating for a particular engine. After opening, it will not close again until oil pressure has dropped approximately 35 kPa (5 psi) less than the opening pressure.

The oil pressure step switch ESS(OPSS) at line 17 is operated only by engine speed, not by oil pressure. When oil pressure is the same as or above the step oil pressure speed setting (this setting is adjustable), ESS(OPSS) is energized. However, the ESS(OPSS) switch has a built-in 9 second delay before it can close across terminals ESS-14 and ESS-13. This makes sure that engine oil pressure has time to increase enough to open OPS2, or system could constantly activate engine shutdown.

Engine Running At Any Speed Below Oil Step Speed Setting

If the engine continues to run at a speed below the oil step speed setting, oil pressure step switch ESS(OPSS) at line 17 remains open and will not complete the circuit to shutdown (even though OPS2 switch at line 17 is closed across contacts OPS2-1 and OPS2-3). Since engine oil pressure has increased enough to open OPS1 switch (line 15) across contacts OPS1-1 and OPS1-3, the engine can safely run at this speed and the oil pressure circuit will not cause shutdown.

If the engine is accelerating through the oil step speed setting, the circuit could still look the same as described above. When engine speed is the same as (or goes above) the oil step speed setting, engine oil pressure must increase enough (above the OPS2 switch rating for a particular engine) to open OPS2 (line 17) within the 9 second time delay of oil pressure step switch ESS(OPSS). The OPSS switch (line 17) will close across contacts ESS-14 and ESS-13 after 9 seconds. At this time, if OPS2 is still closed across contacts OPS2-1 and OPS2-3, engine shutdown will occur. If OPS2 has opened before OPSS has closed, the engine will continue to run.

Engine Normal Stop

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

When moved to STOP position, SSS closes across contacts SSS-5 and SSS-6 (line 24) to allow current to flow through time delay relay (TD) contacts TD-6 and TD-7 (line 36) to energize slave relays (SR1) and (SR2). Relay SR1 (line 36) will now close across its contacts SR1-1 and SR1-3 (line 43) to energize the gas shutoff valve (GSOV) (line 42). The GSOV will now stop the fuel to the engine. At the same time, relay SR2 (line 33) closes across its contacts SR2-1 and SR2-3 (line 47) to connect the magneto (MAG) (line 47) to ground and stop current flow to the spark plugs.

NOTE: On an ETR circuit, contacts SR1-1 and SR1-2 (line 45) will open and stop current flow to de-energize the gas shutoff valve (GSOV) (line 46) to stop fuel to the engine.

After complete engine shutdown is accomplished, the electronic speed switch ESS(CT) closes across terminals ESS-11 and ESS-12 (line 9) to allow for restart. The engine can now be immediately restarted.

Emergency Stop Switch (ES)

The emergency stop switch (ES) is a red, mushroom shaped pushbutton that is located on the front of the junction box door. This pushbutton will shut the engine down and will also prevent the engine from being restarted, because it locks in the OFF (in) position.

When pushed in, ES creates an open circuit across contacts ES-1A and ES-2A (line 9). At the same time, it closes across contacts ES-3A and ES-4A (line 33) to energize both slave relays (SR2) (line 33) and (SR1) (line 36).

Relay SR2 now closes its normally open contact (line 47) to connect the magneto (MAG) to ground and stop current flow to the spark plugs. SR2 remains energized until ESS(CT) contacts ESS-10 and ESS-11 (line 13) open again after the engine stops.

Relay SR1 (line 36) is also energized through ES-3A and ES-4A. SR1 closes its normally open contact (line 43) and opens its normally closed contact (line 45). At this point on an ETS system, the gas shutoff valve (GSOV) is energized. On an ETR system, current flow to the gas shutoff valve (GSOV) is stopped. This stops the fuel to the engine.

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To prevent personal injury due to accidental starting of the engine, disconnect the batteries during maintenance or repair work.

Before starting the engine again, do the steps that follow:

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

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Unburned gas left in the manifold can ignite when the engine is restarted.

2. Before restarting any gas engine which was stopped by grounding the magneto, crank the engine with the gas valve turned off, and the magneto grounded, for 10-15 seconds. This will clear the unburned gas from the exhaust system.

3. Make sure the ES has been reset (pushbutton is out) on the engine junction box. To reset, turn the pushbutton in the direction shown on the button face.

4. Start the engine again with the Start-Stop Switch (SSS).

Fault Circuit Operation

Low Oil Pressure (OPS1)

When the engine is started and begins to run, crank terminate switch ESS(CT) opens across terminals ESS-11 and ESS-12 (line 9) and closes across terminals ESS-11 and ESS-10 (line 13). This immediately arms the system when current is sent to Control 2 (terminal TD-2) of the time delay relay (line 13).

If oil pressure switch (OPS1) (line 15) has not yet opened, the engine oil pressure has 9 seconds (from the time that TD-2 is armed) to increase to the oil pressure rating necessary to open OPS1. If OPS1 does not open, TD contacts will close across terminals TD-6 and TD-7 (line 36) and slave relay (SR1) at line 36 will be energized (current can now flow through contacts OPS1-1 and OPS1-3 to terminal ESS-17 (line 13) and through diode (D4) at line 17, through jumper between TS-9 and TS-10 (line 21), and on through contacts TD-6 and TD-7). SR1 relay contacts will now open across terminals SR1-1 and SR1-2 (line 45), and will close across terminals SR1-1 and SR1-3 (line 43). The gas shutoff valve (GSOV) (line 42) is now energized (ETS) or de-energized (ETR), and will shut the fuel off to the engine.

Relay SR2 also closes its normally open contact (line 47) to connect the magneto (MAG) to ground and stop current flow to the spark plugs.

If the engine had been running (with no faults) at a speed less than the oil step setting, and then lost engine oil pressure, the protection system would cause engine shutdown in the same way as above. OPS1 would close across contacts OPS1-1 and OPS1-3 (line 15) when oil pressure decreased to the minimum switch pressure rating, and engine shutdown would occur immediately.

When oil step latch at terminal ESS-17 was energized in both of the above examples, ESS(CT) contacts 11 and 12 remain open until 2 seconds after speed can no longer be detected. Any attempt to start the engine (until 2 seconds after flywheel rotation has stopped) will be cancelled. This prevents mechanical damage between the starter motor pinion and the flywheel ring gear.

Low Engine Oil Pressure (OPS2)

This condition will only exist if oil pressure switch (OPS2) is used and there is a fault in the high pressure side of the oil pressure circuit. When engine oil pressure drops below the higher pressure rating of OPS2, the switch will close across contacts OPS2-1 and OPS2-3 (line 17). Since the engine has been running at a speed above the step oil pressure setting, the ESS(OPSS) switch at line 17 is already closed. This now makes the circuit complete for current flow to oil step latch at terminal ESS-17. The presence of voltage on ESS-17 causes the oil step contacts OPSS 13 and 14 to be held closed 2 seconds after engine speed can no longer be detected. Current then flows through diode (D4) (line 17), through jumper across terminals TS-9 and TS-10 (line 20), through time delay contacts TD-6 and TD-7 (line 36), and on to energize slave relay (SR1) at line 3.

When SR1 is energized, the normally closed switch now opens across contacts SR1-1 and SR1-2 (line 45) and closes across contacts SR1-1 and SR1-3 (line 43). The circuit is now completed to energize (ETS) or de-energize (ETR) gas shutoff valve (GSOV) at line 42, and the fuel is stopped to the engine.

Relay SR2 is also energized and closes its normally open contact (line 47) to connect the magneto (MAG) to ground and stop current flow to the spark plugs.

Engine Overspeed (OS)

When engine speed increases above the overspeed setting (118% of rated engine speed) of the electronic speed switch (ESS), the overspeed switch ESS(OS) will close across terminals ESS-8 and ESS-7 (line 29). This completes the circuit from the battery through crank terminate ESS(CT) switch across terminals ESS-11 and ESS-10 (line 13), through ESS(OS) switch to both slave relays [through diode (D2) at line 31 to SR2 (line 33) and SR1 (line 36)].

Both SR1 and SR2 are now energized at the same time. SR2 will close across contacts SR2-1 and SR2-3 (line 47) to connect the magneto (MAG) to ground and stop current flow to the spark plugs. At the same time, SR1 will open across contacts SR1-1 and SR1-2 (line 45) and close across contacts SR1-1 and SR1-3 (line 43). The gas shutoff valve (GSOV) at line 42 is now energized (ETS) or de-energized (ETR), and will now shut the fuel off to the engine.

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Unburned gas left in the manifold can ignite when the engine is restarted.

Before restarting any gas engine which was stopped by grounding the magneto, crank the engine with the gas valve turned off, and the magneto grounded, for 10 to 15 seconds. This will clear the unburned gas from the exhaust system.

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

Coolant Overheating

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 water temperature contactor switch (WTS). When WTS (line 18) closes, the circuit is completed across terminals TS-2 and TS-7 (line 18), through diode (D3) at line 19, through jumper between TS-9 and TS-10 (line 21), through time delay contacts TD-6 and TD-7 (line 36) to slave relay (SR1) at line 36 and (SR2) at line 33.

When SR1 is energized, the switch will open across contacts SR1-1 and SR1-2 (line 45) and will close across contacts SR1-1 and SR1-3 (line 43). The gas shutoff valve (GSOV) at line 42 is energized (ETS) or de-energized (ETR) to shut the fuel off to the engine. The starter motor circuit can now be engaged, but engine cannot be restarted (no fuel available) until coolant temperature drops below WTS switch rating, when the switch can open again.

Relay SR2 is also energized and closes its normally open contact (line 47) to connect the magneto (MAG) to ground and stop current flow to the spark plugs.

2301 Electric Governor Control System

When the 2301 Electric Governor Control (EGC) is used, all components of the protection system are activated in the same way as discussed with the nonelectric governors.

With this circuit, current normally flows from TS-28 and TS-31 (lines 43 and 44) through preregulator (PR) at line 48 or fuse (F4) into the EGC. When the engine flywheel is in rotation, current also flows through electric governor actuator (EGA) at line 52. When a fault in the system causes current to energize slave relay (SR1), the switch opens across contacts SR1-1 and SR1-2 (line 45) and closes across contacts SR1-1 and SR1-3 (line 43).

When the circuit is opened across contacts SR1-1 and SR1-2, 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 or carburetor control linkage to shut the fuel off to the engine.

NOTE: Except for the above differences, all fault circuits for the protection system are the same for the 2301 Electric Governor as for the nonelectric governors.

Junction Box (OP, WT, OS) - For Use With Switchgear That Has A Cranking Panel

JUNCTION BOX - 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. Base. 8. Slave relays (SR1 & SR2). 9. Jumpers. 10. Time delay relay (TD). 11. Grommets. 12. Circuit breakers (CB).

Introduction

This junction box circuit (full system without switchgear) is not an independent system. It is designed for the customer who already has his own switchgear. After the customer switchgear is wired into this junction box, it becomes functional and will monitor engine overspeed, oil pressure, coolant temperature and starter motor overspeed.

The junction box contains an electronic speed switch (ESS), a time delay relay (TD), two slave relays (SR1 activates the gas shutoff valve and SR2 connects the magneto to ground), oil pressure switch(s) (OPS) and a water temperature switch (WTS). With the system, both slave relays remain de-energized in order for the engine to run. Also, the gas shutoff valve can either be energized to run (ETR) or energized to shut-off (ETS).

Electrical Schematic And Wiring Diagrams

To follow the circuit operations and find component locations (line reference numbers), see Electrical Schematic Form No. SENR3469 in the separate Electrical Schematic Section of this Service Manual. This schematic includes both the IEC (International Electro-Technical Commission) and the JIC (Joint Industrial Council) symbols.

The point-to-point wiring diagrams for the junction box can be found in the Wiring Diagrams Section of this module.

Circuit Operation

The circuit operation of this system will function the same as the Full Independent System except for the operation of the start-stop switch (SSS). To interface with customer supplied switchgear, use the suggestions (for a three position type start-stop switch) that follow:

1. Connect switch so that START position contacts are across J box terminal strip terminals TS-21 and TS-26.

2. Connect switch so that one side of RUN position contacts go to J box terminal strip terminals TS-8 and TS-7. Connect other side of RUN position contacts to TS-10.

3. Connect switch so that STOP position contacts are across J box terminal strip terminals TS-4 and TS-10.

NOTE: To avoid premature engine shutdown, switch must be held in the START position until oil pressure is seen on the oil pressure gauge.

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-7 and TS-8, and across terminals TS-8 and TS-10.

2. Connect a START switch across J box terminal strip terminals TS-21 and TS-22.

3. Connect a STOP switch across J box terminal strip terminals TS-4 and TS-10.

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.

Wiring Diagrams

Introduction

The section that follows contains point-to-point junction box wiring diagrams and also the junction box wiring harness diagrams. 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.

Refer to Form No. SENR3211, Symbols and Wiring Codes, for an explanation of the number coding on both ends of each wire in the wiring harness.

JUNCTION BOX WIRING HARNESS ETS FULL PROTECTION-OIL PRESSURE, WATER TEMPERATURE, OVERSPEED (Switchgear Included With or Without a Cranking Panel)

JUNCTION BOX WIRING DIAGRAM ETS FULL PROTECTION-OIL PRESSURE, WATER TEMPERATURE, OVERSPEED (Switchgear Without Cranking Panel)

JUNCTION BOX WIRING DIAGRAM ETS FULL PROTECTION-OIL PRESSURE, WATER TEMPERATURE, OVERSPEED (Switchgear With Cranking Panel)