FLOOR-STANDING SWITCHGEAR Caterpillar

The engine control switch on the automatic start-stop control panel is an automatic control switch (ACS). The four positions of the automatic control switch (ACS) are: OFF/RESET, AUTO, MAN and STOP position.

When the generator is to be used as a standby electric power unit, the automatic control switch is put in the AUTO position. Now, if the normal (commercial) electric power stops, the engine starts and the generator takes the electric load automatically. When the normal (commercial) electric power is ON again, for the electric load, the circuit breaker for the generator electric power automatically opens and the generator goes off the electric load. After the circuit breaker for the generator opens, the engine automatically stops.

When the automatic control switch (ACS) is moved to the MAN position, the engine starts. It is now necessary for the circuit breaker for the generator electric power to be closed manually. If the generator is a standby electric power unit and the automatic control switch (ACS) is in the MAN position when normal (commercial) electric power is ON again, the generator circuit breaker opens and the engine stops automatically the same as when the switch (ACS) is in the AUTO position.

The engine will stop with the automatic control switch (ACS) in either the AUTO or MAN positions if there is a not normal condition in the engine. The not normal condition in the engine that can stop the engine is either low lubricating oil pressure, high engine coolant (water) temperature or engine overspeed (too much rpm). When any of these conditions stops the engine, the light for the not normal condition will stay ON after the engine is stopped. The fourth not normal condition light is ON only when the starting motor runs the amount of seconds for the overcrank timer (engine does not start).

Move the automatic control switch (ACS) to the OFF/RESET position and the not normal condition light goes OFF.

It may be necessary to make a reference to the list of abbreviations for the names of the parts, switches, relays and lights that are on the schematics of the engine control group (ECG).

ACS

AUTOMATIC CONTROL SWITCH

AR

ARMING RELAY

ASO

AIR SHUTOFF SOLENOID

BATT.

BATTERY

BC

BATTERY CHARGER

CB

CIRCUIT BREAKER

CB/a

NORMALLY OPEN CIRCUIT BREAKER AUXILIARY CONTACT

CB/b

NORMALLY CLOSED CIRCUIT BREAKER AUXILIARY CONTACT

CBR

CIRCUIT BREAKER RELAY

CCR

CYCLE CRANK RELAY

CCM

CYCLE CRANK MODULE

CCT

CYCLE CRANK TIMER

CCR

COOLDOWN RELAY

CCM

COOLDOWN MODULE

CDT

COOLDOWN TIMER

CLL

COOLANT LEVEL LOW LIGHT (PREALARM)

CS

CIRCUIT BREAKER CONTROL SWITCH

CTS

CRANK TERMINATION SWITCH

C

CIRCUIT BREAKER CLOSED LIGHT

D

DIODE

DCA

DIRECT CURRENT READING AMMETER

DSS

DUAL SPEED SWITCH

FP

FUEL PRESSURE

GCR

GOVERNOR CONTROL RELAY

GOV.

GOVERNOR

GS

GOVERNOR SWITCH

GSM

GOVERNOR SPEED MOTOR

HWT

HIGH WATER TEMPERATURE LIGHT (PREALARM)

IC

INITIATE CONTACT

LCL

COOLANT LEVEL LOW SWITCH (PREALARM)

LFL

LOW FUEL LEVEL LIGHT (PREALARM)

LFS

LOW FUEL LEVEL SWITCH (PREALARM)

LOL

LOW OIL LEVEL LIGHT (PREALARM)

LWT

LOW WATER TEMPERATURE SWITCH

O

CIRCUIT BREAKER OPEN LIGHT

OCL

OVERCRANK LIGHT

OCR

OVERCRANK RELAY

OCT

OVERCRANK TIMER

OLL

OIL LEVEL LOW LIGHT (PREALARM)

OPL

LOW OIL PRESSURE LIGHT

OPP

LOW OIL PRESSURE PREALARM SWITCH

OPR

LOW OIL PRESSURE RELAY

OPS

LOW LUBE OIL PRESSURE SWITCH

OPT

OIL PRESSURE TIMER

OPTD

OIL PRESSURE TIME DELAY

OSL

OVERSPEED LIGHT

OSR

OVERSPEED RELAY

OSS

OVERSPEED SWITCH

PS

PRESSURE SWITCH

PSW

PRESSURE SWITCH

RPL

REVERSE POWER LIGHT

RPR

REVERSE POWER RELAY

RPRE

REVERSE POWER RELAY RESET SWITCH

RPRX

REVERSE POWER RELAY AUXILIARY

RR

RUN RELAY

SHTC

SHUNT TRIP COIL

SR

SHUTDOWN RELAY

SS

SHUTDOWN SOLENOID

SUP.

SUPPRESSOR

T

TRIP POSITION

WLT

LOW WATER TEMPERATURE LIGHT (PREALARM)

WTL

WATER TEMPERATURE LIGHT (HIGH)

WTP

HIGH WATER TEMPERATURE SWITCH (PREALARM)

WTR

WATER TEMPERATURE RELAY (HIGH)

WTS

WATER TEMPERATURE SWITCH (HIGH)

Standby Condition

When the generator is in the standby condition the automatic control switch (ACS) is in the AUTO position. If the normal (commerical) electric power stops, initiating contact (IC) is closed to make a circuit which activates the starting motor to start the engine.

The numbers that are under some of the names of the components, on the right of the wiring schematics, are for the lines (numbers on the left of the schematic) where the component is located. Some of the numbers under the relays are underlined. The relay contact in the line (with the underlined number) is a normally closed contact.

AUTOMATIC START-STOP SCHEMATIC STANDBY CONDITION

AUTOMATIC START-STOP SCHEMATIC STANDBY CONDITION

Automatic Start

When the automatic control switch (ACS) is in the AUTO position, contact 9 and 10 is closed [see lines 5 and 6]. When commercial power gets stopped, initiating contact (IC) closes. Now there is a complete circuit from the battery (BATT) to activate the run relay (RR). The run relay (RR) contacts [see lines 23, 24 and 7] disconnect the battery charger, if there is one in the panel, open the circuit to the engine shutdown solenoid, if there is one, and makes a circuit to the magnetic switch (MS).

Manual Start

The sequence for MANUAL START is the same as for the AUTOMATIC START except the automatic control switch (ACS) in the MAN position opens contact 10 and closes contact 11 to make a complete circuit through the run relay (RR) [See line 7].

AUTOMATIC START-STOP SCHEMATIC AUTOMATIC START: ENGINE STARTING

Engine Starts

When the engine starts, the engine oil pressure and the engine speed increases. Now the normally open crank termination switch (CTS) closes and the oil pressure switch (OPS) closes the circuit for the arming relay (AR) [see line 10]. The activated arming relay (AR) contact 9 and 3 opens and there is no circuit to the magnetic switch (MS). The open magnetic switch (MS) disconnects the pinion solenoid (PS) from the starting motor (SM) and it stops. When arming relay (AR) contact 9 and 3 opened, the overcrank relay (OCR) is disconnected from the circuit.

At the same time arming relay (AR) contact 9 and 3 opens, arming relay contact 9 and 6 closes to keep the arming relay (AR) in the circuit when the engine is running.

Normally closed run relay (RR) contact 9 and 3 opens when the engine is started [see line 23] and there is no circuit for the shutdown solenoid (SS). At the same time run relay (RR) contact 9 and 3 opens, contact 9 and 6 closes and there is a circuit to the engine governor (see line 24).

When the engine is running any of these switches; oil pressure switch (OPS), water temperature switch (WTS) or overspeed switch (OSS) can close, when it is necessary, the circuit to these respective relays, oil pressure relay (OPR), water temperature relay (WTR) or overspeed relay (OSS) [see lines 11, 12, 16, 18 and 22]. When a circuit to any of these relays is closed, the respective relay contact [see lines 26, 27 and 28] closes the circuit to the shutdown relay (SR).

AUTOMATIC START-STOP SCHEMATIC AUTOMATIC START: ENGINE STARTS

Engine Does Not Start

The overcrank timer (OTC) is in a parallel electric circuit with the starting motor (SM) as shown in the AUTOMATIC START explanation [see lines 2, 9 and 12]. When the circuit for the magnetic switch (MS) is closed to start the engine, the circuit is also through overcrank timer (OTC) and the switch in the timer starts to close. When the starting motor turns the engine crankshaft the amount of seconds for the switch in the overcrank timer (OCT) to close (time for switch to close has an adjustment range of 30 to 45 seconds), the switch closes. Now there is a circuit for the overcrank relay (OCR) [see lines 9, 12 and 13]. The activated overcrank relay (OCR) closes both contact 6 and 9 and contact 7 and 4 [see lines 13 and 25].

Closed overcrank relay (OCR) contact 7 and 4 makes a circuit for shutdown relay (SR). The activated shutdown relay (SR) closes contact 7 and 4 for the shutdown solenoid (SS). The activated shutdown solenoid (SS) moves the fuel rack, for the engine, to the FUEL OFF position. The shutdown relay (SR) contacts 3 and 9 open and there is no circuit for the run relay (RR) [see line 5]. When the circuit for the run relay (RR) opens its contact 4 and 7 opens and there is no circuit for the magnetic switch (MS). Now with the magnetic switch (MS) open, the starting motor (SM) stops.

There is a circuit for both the overcrank relay (OCR) and the overcrank light (OCL) through closed overcrank relay (OCR) contact 6 and 9 and automatic control switch (ACS) contacts 15 and 17 to keep the overcrank light (OCC) ON. For the overcrank light (OCC) to go OFF, the automatic control switch (ACS) must be moved to the OFF/RESET position which opens contact 15 [see line 13].

AUTOMATIC START-STOP SCHEMATIC AUTOMATIC START: ENGINE DOES NOT START

Automatic Shutdown

When normal (commercial) power comes ON again, a transfer switch opens both the circuit breaker for the generator power and the initiating contact (IC) in the automatic control panel (ACP) [see line 6]. Now there is no circuit for the run relay (RR) and both closed contact 4 and 7 and contact 9 and 6 open. Run relay (RR) open contact 9 and 3 closes and there is a circuit for the shutdown solenoid (SS) [see lines 7, 23 and 24]. The activated shutdown solenoid (SS) moves the fuel rack to the FUEL OFF position and the engine stops.

When the engine speed gets slower as the engine stops, the engine oil pressure decreases and the oil pressure switch (OPS) opens the circuit for the arming relay (AR) and the oil pressure timer (OPT). Now the oil pressure timer (OPT) switch opens. [see lines 10, 11 and 14]. When the oil pressure switch (OPS) opened the circuit for the arming relay (AR) it closed the circuit to the open switch in the oil pressure timer (OPT) and the oil pressure light (OPL) can not go ON.

Pressure switch (PSW) has a delay action that keeps the circuit for the shutdown solenoid (SS) closed and the shutdown solenoid (SS) keeps activated for a few more seconds after the engine fuel rack is in the FUEL OFF position. [see lines 21 and 22]. Diode (D2) is to prevent an electric spark (arcing) from the contacts in the shutdown solenoid (SS).

AUTOMATIC START-STOP SCHEMATIC AUTOMATIC START: AUTOMATIC SHUTDOWN

Manual Shutdown

Move the automatic control switch (ACS) from either the MAN or the AUTO position to the STOP position and contact 8 closes [see line 21]. Now there is a circuit for the shutdown solenoid (SS). The activated shutdown solenoid (SS) moves the fuel rack to the FUEL OFF position and the engine stops.

The oil pressure light (OPL) does not go ON when the engine is stopped. See AUTOMATIC SHUTDOWN for this explanation.

AUTOMATIC START-STOP SCHEMATIC ENGINE MANUAL SHUTDOWN

Engine Shutdown Caused By An Engine Operating Condition

The automatic start-stop system uses sensors, some on the engine, to activate the automatic control panel (ACP) to stop the engine if the engine gets any of these not normal conditions:

1. Low oil pressure (oil for engine lubrication) of approximately 8 psi (55 kPa).

2. Starting motor that turns the engine crankshaft for too many seconds and the engine does not start (starting motor operation can be adjusted for 30 to 45 seconds).

3. Engine speed more than 18 to 20% faster (overspeed) than engine rated rpm.

4. High temperature of the coolant in the engine (sensor has a temperature setting adjustment).

Any of these not normal engine conditions close contacts in the sensor, for that condition, which makes a circuit for the shutdown relay (SR) in the automatic control panel (ACP).

Example: The temperature of the coolant in the engine has increased to the setting of the water temperature switch (WTS) and the switch closes. The water temperature switch (WTS) is not a part of the automatic control panel (ACP).

The closed water temperature switch (WTS) makes a circuit for the water temperature relay (WTR). The activated water temperature relay (WTR) contact 7 and 4 closes and contact 6 and 9 closes [see lines 16, 17 and 27]. The closed water temperature relay (WTR) contact 6 and 9 makes a circuit for the water temperature light (WTL) through the automatic control switch contacts 15 and 17 and the water temperature light (WTL) is ON. There is now a parallel electric circuit for both the water temperature relay (WTR) and the water temperature light (WTL). Closed contact 7 and 4, in the water temperature relay (WTR), made a circuit for the shutdown relay (SR). The activated shutdown relay (SR) contact 9 and 3 opens to open the circuit to the run relay (RR) and contact 7 and 4 closes to make a circuit for the shutoff solenoid (SS) [see lines 5, 21 and 22]. The activated shutoff solenoid (SS) moves the fuel rack to the FUEL OFF position and the engine stops.

After the engine has stopped, the temperature of the coolant decreases and the water temperature switch (WTS) opens. The water temperature light (WTL), for the not normal engine condition, does not go OFF when the water temperature switch (WTS) opens because of the circuit through the automatic control switch (ACS) contacts 15 and 17.

Procedure For Starting The Engine After A Shutdown Caused By An Engine Condition

1. Move the automatic control switch (ACS) to the OFF/RESET position (the light for the not normal condition in the engine will go OFF).

2. Correct the cause for the not normal condition for the engine shutdown.

3. Move the automatic control switch (ACS) to the MAN position. After the engine has started make the tests necessary to be sure the condition for the engine shutdown was corrected.

NOTE: If the engine shutdown was caused by too fast engine condition (overspeed) it may be necessary to activate another control, for the overspeed condition, before the engine can be started.

AUTOMATIC START-STOP SCHEMATIC AUTOMATIC START: HIGH WATER TEMPERATURE ENGINE STOP

Maintenance

Make a regular program for switchgear inspection and maintenance. The period between each inspection for the program, that was made, can be either shorter or longer when the condition of the switchgear after each inspection has an indication that the period between each inspection was not correct.

Disconnect all power from the switchgear (generator and/or commercial power). Nothing in the switchgear can be activated when components and wires must be felt when inspection and maintenance work is done.

Inspect the insulation or the wires for breaks and for wear. Be sure that the wire insulation is in good condition. Inspect all wire connections to be sure the connections are clean and tight. Because some loose wire connections can not be seen, it is important to feel the wire connections to be sure they are tight.

The maintenance and inspection program that follows can be used as a reference for a regular maintenance and inspection program.

1. Each week. Inspect the condition of the wire connections and the wire insulation. Manually test the operation of the circuit breakers. Tighten loose connections. Install new wire where necessary.

NOTE: An inspection of the contacts of the circuit breaker must be made if some electric failure (short circuit) opened the circuit breaker. Be sure the power is disconnected from the switchgear when the inspection is made.

2. Every three months. The each week inspection and the condition and now the operation of the automatic control panel shutdown circuits.

3. Each year and engine electric set overhaul. The each week inspection, the every three months operation and clean the complete switchgear. A vacuum cleaner is good for removing loose dirt. Dry air with a pressure of not more than 30 psi (205 kPa) can be used to get the dirt out of small openings and corners. Use a cloth (that has not been used to clean oil off of something) and clean all of the components, terminal boards and wire connections. Inspect the condition of the bus bars and the bus bar supports. The bus bar connections must be clean and the bolts and nuts through the bus bars must be tight. Inspect the pins and sockets of the relays and clean the sockets and install a new relay if necessary. Install new resistors if the inspected relays look damaged. A complete inspection of the circuit breaker. See the circuit breaker manufacturers literature.

Storage

When it is necessary to put the switchgear in storage the switchgear must be correctly prepared for storage. Any damaged switchgear parts can be repaired or new parts installed. All wires need an inspection for loose connection and damaged insulation. Install new wires when necessary.

1. Remove all of the dirt and dust from the switchgear and on the parts.

2. Put a good amount of water (moisture) absorbant powder in each compartment.

NOTE: This is not necessary if the switchgear is to be in a dry place for storage.

3. Cover the switchgear with material that will keep water away from the switchgear.

4. Either put the switchgear in a crate or build a cover around it if there can be something to bump against the switchgear and damage it.

When the switchgear is removed from storage:

1. Remove the cover (material, crate or box).

2. Use a soft cloth and wipe any water (moisture) from the inside of the panel and from the parts and wires.

3. Inspect all of the wires for broken or missing insulation and tighten all loose connections.