Murphy MC-900 User Manual

SERIES MC-900 MURPHYMATIC

®

MANUAL GENERATOR

ENGINE CONTROL SYSTEM

DESIGN, INSTALLATION

AND OPERATING MANUAL

MC-9142N

Revised 12-00

Section 40

(00-02-0202)

Table of Contents

Section 1: Introduction page 1

1-1 System ............................................................................................................................................... 1

1-2 Models ............................................................................................................................................... 1

1-3 Purpose .............................................................................................................................................. 1

1-4 Definitions ......................................................................................................................................... 1

1-5 How To Use This Manual ............................................................................................................... 1

Section 2: Specifications 1

2-1 Enclosure Type ................................................................................................................................. 1

2-2 Power Requirements ........................................................................................................................ 1

2-3 Input Ratings .................................................................................................................................... 1

2-4 Output Ratings ................................................................................................................................. 1

2-5 Field Wiring Connections ................................................................................................................ 1

2-6 Operating Temperature ................................................................................................................... 1

Section 3: Model Identification 1

3-1 Model Numbers ................................................................................................................................ 1

3-2 MC-900 .............................................................................................................................................. 2

3-3 MC-900-2 .......................................................................................................................................... 3

Section 4: Installation 3

4-1 Location ............................................................................................................................................ 3

4-2 Wiring ............................................................................................................................................... 3

4-3 Overspeed Switch ............................................................................................................................. 7

4-4 Pre-Operational Check-Out ............................................................................................................ 7

Section 5: Operation 8

5-1 Operator Controls ............................................................................................................................ 8

5-2 Operating Modes .............................................................................................................................. 8

Section 6: Routine Maintenance and Operational Tests 8

6-1 Routine Maintenance ....................................................................................................................... 8

6-2 Operational Tests ............................................................................................................................ 8

Section 7: Troubleshooting and Repair ...................................................................................... 8

7-1 Tools Required .................................................................................................................................. 8

7-2 MC-900 SELECTRONIC®Control Operation and Shutdown ................................................... 9

Section 8: Replacement Parts 11

8-1 Replacement Parts ........................................................................................................................... 11

8-2 Replacement Parts Detroit Diesel Modules ................................................................................... 11

Section 1: Introduction

1-1 System.
1-1.1 The MURPHYMATIC®Manual Generator Engine

Control System, Series MC-900 is designed to meet the
requirements of the engine control and shutdown for manual
start generator engines.
By combining one of the MC-900 series controls with generator
instruments, a complete engine generator control panel can be
provided.

1-2 Models.
1-2.1 The Series MC-900 is available in two basic

configurations:
1-2.1.1 Model MC-900 for manual start and stop generator sets
with four cycle engines which includes the minimum normal
shutdowns.
1-2.1.2 Model MC-900-2 for manual start and stop generator
sets with two cycle engines which includes the minimum normal
shutdowns and an “Overspeed Relay” to operate the air shutoff
solenoid for overspeed shutdown.

1-2.2 Both models are available for 12 or 24 volt operation.
1-2.3 Both models include four unlabeled shutdown circuits for

additional customer specified shutdowns.
1-2.4 Each model is made up of two parts, a Control/Display
module and a Relay module.

1-3 Purpose.
1-3.1 This manual is directed to the installation, maintenance

and operating personnel who will be in day to day contact with
the MC-900 system.
1-3.2 No manual can cover all aspects of a product. However
the basic knowledge gained with this material will allow those
personnel to easily adjust to special circumstances.

1-4 Definitions.
1-4.1 Throughout this manual, reference is made to

organizations, trade names and trademarks which may not be
familiar to the reader. Some of these are:

1-4.1.1 NFPA: National Fire Protection Association.
1-4.1.2 NFPA-70: The National Electrical Code.
1-4.1.3 Several terms used in this manual are registered

trademarks of Frank W. Murphy Mfr.

(a) MURPHYMATIC®: Refers to all Murphy automatic

controls.

(b) SELECTRONIC®: A name that is applied to all electronic

controls manufactured by Murphy.

(c) SWICHGAGE®: A combination indicating gauge and

switch.

(d) TATTLETALE®: A term that refers to a shutdown

indicating device or circuit in the control panel.

1-5 How to use this manual.
1-5.1 Section 1, 2, 4, 5, 6 and 7 contain general information that

applies to all MC-900 models.
1-5.2 Section 3, Model Identification, is broken into three sub
sections. Section 3-1 allows you to chose the model that best
fits your requirements and Section 3-2 and 3-3 explain each
models features in detail.

Section 2: Specifications

2-1 Enclosure Type.
2-1.1 The MC-900 Series enclosure is designed to be mounted

in a standard electrical enclosure for indoor use.
2-1.2 The MC-900 Series shares the same enclosure as the A­900 automatic start controller so they can be used
interchangeably in a generator control panel.

2-2 Power Requirements.
2-2.1 The engine controls, shutdown circuits and shut-down

indicators are powered from the engine starting battery. The
MC-900 series is available in either 12 or 24 volt, negative
ground.

2-2.2 The MC-900 is fused for 3 amp. maximum current.

2-3 Input Ratings.
2-3.1 All input switches should be dry contact type, maximum

current is 2 ma, 8 VDC or less.
2-3.2 Frequency signal for the speed sensing circuit requires a
minimum input of 2 volts RMS from a magnetic pickup
(preferred) or from the tachometer terminal of the battery
charging alternator.
2-3.2.1 Frequency range of the speed sensing circuit is 300 Hz
to 10,000 Hz.

2-4 Output Ratings.
2-4.1 The MC-900 Control / Display Module has outputs for

remote indication of shutdowns. These outputs are transistors
that close to the negative supply (sink) and are rated at 1 amp,
30 VDC maximum.
2-4.2 The Control / Display Module also has an output for an
auxiliary starter contactor which is rated 1 amp, 30 VDC
maximum. This is a transistor that closes to the positive supply
(source).
2-4.3 The Relay Module includes 3 engine control relays with
contact ratings of 7 amp, 30 VDC inductive. These powered
contacts must be suppied from an 8 amp. fuse or circuit breaker
(customer supplied).

2-5 Field Wiring Connections.
2-5.1 All field wiring connections are barrier terminal blocks,

UL rated for 15 amp, 300 volt.

2-6 Operating Temperature.
2-6.1 The operating temperature range of the MC-900 is -4°F to

158°F / -20°C to 70°C.

Section 3: Model Identification

3-1 Model Numbers.
3-1.1 MC-900-12 and MC-900-24: These models are designed

for a manual start four cycle engine driven generator, and
include the minimum shutdown points normally supplied on
such installations. The suffix numbers -12 and -24 indicate the
engine starting battery voltage.
3-1.2 MC-900-2-12 and MC-900-2-24: These models are
designed for a manual start two cycle engine driven generator,
and include the minimum shutdown points normally supplied on
such installations. The suffix numbers -12 and -24 indicate the
engine starting battery voltage.
3-1.2.1 The MC-900-2 series control includes an “Overspeed
Relay” to trip the air shut-off solenoid on overspeed of a two
cycle engine.

1

3-2 MC-900.
3-2.1 Control / Display Module. The Control / Display

Module, figure 3-2.1, includes the control and test switches,
the solid state logic elements and shutdown TATTLETALE

®

lights that make up the generator engine control for a four
cycle engine.

3-2.1.1 Mode Selector Switch, OFF-RUN-START:

(a) OFF; turns off the control system and resets any

shutdown circuits.

(b) RUN; turns on the engine controls and shutdown

circuits. System is on, waiting for the engine to start.
Switch returns to run position from START after starting
engine.

(c) START; turns on the engine start circuit. A start signal is

applied to the auxiliary start solenoid and the engine
starter engages. Releasing the start switch disconnects
cranking.

3-2.1.2 Lamp Test Pushbutton: Tests the lights on the MC-900
module when the Mode Selector Switch is in the RUN
position.
3-2.1.3 The MC-900 SELECTRONIC

®

Control Module

includes the following engine control features:

(a) Overcrank circuit; will stop manual cranking and

indicate overcrank if start switch remains closed longer
than the overcrank time setting. The crank time is
selectable for 10, 15, 20, 25 or 30 seconds before
shutdown.

(b) Shutdown Time Delay Bypass; this delay prevents the

oil pressure and water temperature shutdown circuits
from operating for 30 seconds after the engine starts as
detected by the Mode Selector Switch returning to RUN

position. This same delay can also lock out all other
shutdown circuits except Overspeed and Overcrank.
The user may select which circuits are locked out by the
time delay bypass.

(c) Overspeed Speed Switch;

1. Provides a signal to the overspeed shutdown circuit
if the engine exceeds the preset speed. The factory
setting is approximately 3894 Hz, or 1980 RPM on
an engine with 118 teeth on the flywheel ring gear.
The adjustment range is 300 Hz to 10,000 Hz.

2. A push to test switch is provided to allow testing of
the overspeed circuit without overspeeding the
engine. When switch is depressed, the set point of
the speed switch is lowered approximately 10%.

3. The push to test switch can also be used to set the
overspeed switch at approximately 110% of running
speed. Hold the switch depressed while adjusting the
setting until the overspeed trips. When switch is
released, the set point will be 10% above normal
running speed. This is the method used to make the
factory setting. With engine speed at 1800 RPM or
3540 Hz.

3-2.1.4 Eight (8) First-out Shutdown Circuits; provide first­out indication of cause of shutdown. These circuits deactivate
the fuel relay and lockout the MC-900 until reset. Shutdown
circuits are activated by the Mode Selector Switch and or
Shutdown Time Delay Bypass. Eight (8) Red Shutdown
Indicating Lights are provided.

(a) Overcrank; tripped by the overcrank timing circuit

which times as long as the START switch is closed.

(b) Overspeed; tripped by overspeed switch when engine

exceeds a preset speed.

(c) Oil Pressure; tripped by the oil pressure SWICHGAGE

®

if pressure drops below preset point while the engine is
running.

(d) Water Temperature; tripped by the water temperature

SWICHGAGE®if engine coolant temperature exceeds
the switch setting.

(e) Spare Shutdowns; tripped by an external switch. These

circuits are provided for additional shutdowns that may
be recommended by the engine supplier or required by
the user.

3-2.2 Relay Module. The Relay Module, figure 3-2.2,
includes all of the control and shutdown relays that are
required to make up the generator engine control. Relays are
available for operation on either 12 or 24 volt battery systems.
Two (2) relays are included for:
3-2.2.1 Fuel Relay; this relay provides two outputs, one to
energize the engine fuel solenoid and a separate circuit to
energize the battery charging alternator field.
3-2.2.2 Shutdown Relay; this relay is operated by the
shutdown circuits of the Control / Display Module and
provides an output that can be used to trip the generator circuit
breaker on an emergency shutdown.
3-2.3 Status Signal; The relay module also includes an output
that can be used with external circuits for signaling or control
functions.
3-2.3.1 The Run signal at terminal 17 is on (closed to
negative) as long as the Mode Selector Switch is in either Run

2

Figure 3-2.1

6-15/32 in.

(164 mm)

Oil Pressure

Water

Temperature

9-3/4 in.

(248 mm)

Overcrank

Overspeed

Lamp Test

OFF

RUN

START

or Start and no shutdown TATTLETALE®circuit is latched on.
This can be used to signal that the generator engine is ready to
start or is running.

3-3 MC-900-2.
3-3.1 Control / Display Module. The Control / Display

Module, figure 3-2.1, is also used as on the Model MC-900-2.
3-3.2 Relay Module. The Relay Module, figure 3-3.2,
includes all of the control and shutdown relays that are
required to make up the generator engine control. Relays are
available for operation on either 12 or 24 volt battery systems.

Three (3) relays are included for:
3-3.2.1 Fuel Relay; this relay provides two outputs, one to
energize the engine fuel solenoid and a separate circuit to
energize the battery charging alternator field.
3-3.2.2 Shutdown Relay; this relay is operated by the
shutdown circuits of the Control / Display Module and
provides an output that can be used to trip the generator circuit
breaker on an emergency shutdown.
3-3.2.3 Overspeed Relay; operates only on an Overspeed

shutdown. This relay provides an output to trip an air shut off
solenoid to close the air damper on a two cycle engine.
3-2.3 Status Signal; The relay module also includes an output
that can be used with external circuits for signaling or control
functions.

3-2.3.1 The Run signal at terminal 17 is on (closed to
negative) as long as the Mode Selector Switch is in either Run
or Start and no shutdown TATTLETALE

®

circuit is latched on.
This can be used to signal that the generator engine is ready to
start or is running.

Section 4: Installation

4-1 Location.
4-1.1 The MC-900 series is designed to mount in a

MURPHYMATIC®Generator Control panel with the Control /
Display module on the front panel and the Relay module on
the inside bottom surface. Other types of installation is
possible as long as the relationship of the two modules are
maintained.
4-1.2 Clearance for Installation and Service; The modules
must be accessible for wiring to the terminal blocks and
adjustment of the user controls on the back of the Control /
Display module. Figure 4-1.2 shows the mounting dimensions
and the minimum clearances recommended for installation.
4-1.3 Wiring Terminals; Terminal blocks are provided on
both sides of the Control / Display enclosure and the Relay
Module. Torque all terminal screws to 12 inch pound
maximum.

4-2 Wiring.
4-2.1 After the MC-900 has been located and installed, the

wiring connections can be made. This work should be done
with all electrical power disconnected from the engine. BE
SURE THAT THE BATTERY IS DISCONNECTED.
4-2.2 All electrical installation work should be done in
accordance with the National Electrical Code, NFPA-70, and
all applicable local codes.
4-2.3 In general, the following connections will be made:

(a) Battery positive and negative.
(b) Engine run device, such as a fuel shutoff solenoid.
(c) Engine speed sensor, such as a magnetic pickup or the

tachometer output of a battery charging alternator.

(d) Engine starter circuit; an auxiliary starter solenoid is

required to handle most starter solenoid requirements.

(e) Shutdown sensing switches as required.

4-2.3.1 The complete wiring of a Model MC-900 control is
shown in figure 4-2.3.1. Provision is made in the MC-900
series to operate remote lights for all of the shutdown circuits
however these circuits do not have to be wired for the MC-900
to function.
4-2.3.2 Figure 4-2.3.2 is for wiring of the MC-900-2 control.
The same provisions as for the MC-900 are made.
4-2.3.3 Wire Termination; the terminal blocks that are
supplied requires that all wires be terminated with #6 stud size
forked spade solderless wire connectors or stripped and
inserted under the captive terminal plates. Torque all terminal
screws to 12 inch pound maximum.
4-2.3.4 All inductive loads (relays-soleniods-coils-etc.) that
are connected to the MC-900 must have reverse diodes wired

3

Figure 3-3.2

TB1

Figure 3-2.2

Torque

Terminal

12 lbs

J1

For continued protection against
fire & shock hazard, replace only
with same type fuse & rating.

1

4

5

6

RH2V2

7

DC12V

8

9

10

11

12

13

14

WARNING

3AMP Fuse

-U

4-1/2 in.

(114 mm)

RH2V2

-U

DC12V

J2

TB2

15

4

16

17

18

19

20

21

22

23

24

25

Torque

Terminal

12 lbs

6-1/4 in.

(159 mm)

TB1

Torque

Terminal

12 lbs

J1

For continued protection against
fire & shock hazard, replace only
with same type fuse & rating.

1

4

5

6

7

8

9

10

11

12

13

14

WARNING

3AMP Fuse

RH2V2

-U

DC12V

4-1/2 in.

(114 mm)

RH2V2

-U

DC12V

RH2V2

-U

DC12V

J2

TB2

15

4

16

17

18

19

20

21

22

23

24

25

Torque

Terminal

12 lbs

6-1/4 in.

(159 mm)

4

Mounting

Figure 4-1.2: Dimensions

Holes
1/8 in.
(3 mm)
diameter

1-1/2 in.

(38 mm)

clearance

4-15/32 in.

(114 mm)

6 in.

(152 mm)

3 in.

(76 mm)

2-13/16 in.

5-5/8 in.

(143 mm)

(71 mm)

1-1/2 in.
(38 mm)

clearance

6-3/4 in.

(171 mm)

3-3/8 in.
(86 mm)

9-3/8 in.

(238 mm)

NOTE:

Clearance
required for
wire run.

5 in. (127 mm) maximum

between MC-900 and relay module

3/16 in.

(5 mm) dia.

4 places

5-1/2 in.

(140 mm)

1-7/8 in.
(48 mm)

clearance

3-3/4 in.

1-7/8 in.

(95 mm)

(48 mm)

clearance

5

Figure 4-2.3.1: MC-900 wiring

Hourmeter Voltmeter

+– –+

Input
Barrier
Terminal
Blocks

MANUAL START

15

FUSE B+ OUT
B– TO HOURMETER

26

B GROUND

4

27

MAGNETIC PICKUP
LOW OIL PRESS.

28

GROUND

4

29

HIGH WATER TEMP.

30

SPARE #1 SHUTDOWN INPUT

31

SPARE #2 SHUTDOWN INPUT

32

SPARE #3 SHUTDOWN INPUT

33

SPARE #4 SHUTDOWN INPUT

34

MODULE

OVERCRANK LIGHT OUTPUT

OVERSPEED LIGHT OUTPUT

LOW OIL PRESS. LIGHT OUTPUT

HIGH WATER TEMP. LIGHT O/P

SPARE #1 LIGHT OUTPUT
SPARE #2 LIGHT OUTPUT

SPARE #3 LIGHT OUTPUT
SPARE #4 LIGHT OUTPUT

35
36
37
38
39
40
41
42
43
44
45
46

Output

Barrier

Terminal

Blocks

B+

Battery

Starter

Auxiliary Starter

Solenoid

B+

B– Ground

(FR) Energize to Stop solenoid

(FR) Energize to Run solenoid

Fuel relay N.C. dry contact

Fuel relay Com. dry contact

Fuel relay N.O. dry contact

(SDR) Circuit breaker shunt trip

TB1

1
4
5
6
7
8

9
10
11
12
13
14

B+

B–

A BABC D E

J1

Fuel
Relay

3A Fuse

J2

A

Over
Speed
Relay

FUEL RELAY

SHUTDOWN RELAY

OVERSPEED RELAY

CRANK SIGNAL

RUN SIGNAL

J2

Shut
Down
Relay

J2

B

J2

C

TB2

Lamp

15

4

B+ to aux. starter solenoid

16

Run signal switched B–

17

Shutdown relay N.C. dry contact

18

Shutdown relay COM. dry contact

19

Shutdown relay N.O. dry contact

20

Overspeed relay N.C. dry contact

21

Overspeed relay COM. dry contact

22

Overspeed relay N.O. dry contact

23
24
25

6

Figure 4-2.3.2: MC-900-2 wiring

Hourmeter Voltmeter

+– –+

Input
Barrier
Terminal
Blocks

MANUAL START

15

FUSE B+ OUT
B– TO HOURMETER

26

B GROUND

4

27

MAGNETIC PICKUP
LOW OIL PRESS.

28

GROUND

4

29

HIGH WATER TEMP.

30

SPARE #1 SHUTDOWN INPUT

31

SPARE #2 SHUTDOWN INPUT

32

SPARE #3 SHUTDOWN INPUT

33

SPARE #4 SHUTDOWN INPUT

34

MODULE

OVERCRANK LIGHT OUTPUT

OVERSPEED LIGHT OUTPUT

LOW OIL PRESS. LIGHT OUTPUT

HIGH WATER TEMP. LIGHT O/P

SPARE #1 LIGHT OUTPUT
SPARE #2 LIGHT OUTPUT

SPARE #3 LIGHT OUTPUT
SPARE #4 LIGHT OUTPUT

35
36
37
38
39
40
41
42
43
44
45
46

Output
Barrier

Terminal

Blocks

B+

Battery

Starter

Pressure

Fuel

Auxiliary Starter

Solenoid

B+

B– Ground

(FR) Energize to Stop solenoid

(FR) Energize to Run solenoid

Fuel relay N.C. dry contact

Fuel relay Com. dry contact

Fuel relay N.O. dry contact

(SDR) Circuit breaker shunt trip

(OSR) Air damper solenoid

TB1

1
4
5
6
7
8

9
10
11
12
13
14

B+

B–

FUEL RELAY

A BABC D E

J1

3A Fuse

Fuel
Relay

Over
Speed
Relay

J2

A

SHUTDOWN RELAY

OVERSPEED RELAY

CRANK SIGNAL

RUN SIGNAL

J2

Shut
Down
Relay

J2

B

J2

C

TB2

Lamp

15

4

B+ to aux. starter solenoid

16

Run signal switched B–

17

Shutdown relay N.C. dry contact

18
19

Shutdown relay COM. dry contact

Shutdown relay N.O. dry contact

20

Overspeed relay N.C. dry contact

21

Overspeed relay COM. dry contact

22

Overspeed relay N.O. dry contact

23
24
25

7

across the coil to suppress reverse voltage that is generated
whenever the inductive load is de-energized. This will protect
the electronic components in the MC-900 and should prevent
operating malfunction due to noise. The “rule of thumb” for
sizing the reverse diode is to use one with a PIV (Peak Inverse
Voltage) rating equal to the operating voltage or at least 100
volts and a current rating that is equal to or greater than the
forward current that the coil draws to operate. For example, a
relay less than 1 A, use a 1 A diode since they are readily
available. The wiring shown in figures 4-2.3.1 and 4-2.3.2 have
examples of the places that a reverse diode is required.

4-3 Overspeed Switch.
4-3.1 A magnetic pickup is recommended to supply the speed

signal for the MC-900 series overspeed switch. This pickup
will be mounted in the flywheel housing in line with the ring
gear on the flywheel and wired to the MC-900 using either a
twisted pair or a shielded cable to reduce the possibility of
electrical noise pickup in the wiring.
4-3.2 The tachometer terminal, of the battery charging
alternator, may be used for the speed signal but a broken drive
belt will disable this source and some alternators have
electrical noise which will cause the speed switches to operate
at speeds well below the desired RPM.

4-4 Pre-operational Check-out.
4-4.1 After installation is complete, it is necessary to make

some adjustments to the MC-900 SELECTRONIC®Control
before the system is operational. All shutdown circuits also
should be tested. Table 4-4.1 lists the standard factory setting
of the adjustable functions on the MC-900 series control. To
determine if the frequency of the speed switch must be
changed, calculate the required setting using the following
formulas:

Refer to Table 4-4.1 to determine if the speed switch setting is
below the factory setting listed. If required frequency will be
higher than the standard, increase the setting before
proceeding. Turn the Overspeed Set pot clockwise to increase
setting. The adjustment is a 20 turn control without stops at
either end.

4-4.1.1 Be sure to have a fully charged battery to do these
tests. Low battery voltage can cause improper results during
the tests.

4-4.1.2 All of the adjustments and controls shown in Table 4-

4.1 are located on the rear of the control/display module. See
Figure 4-4.1.2. Each light and switch is labeled for ease of
identification. The LED’s are supplied as an aid in installation
and troubleshooting of the MC-900.

4-4.2 Start and Stop Engine; to test the start and stop function,
proceed as follows:

(a) Double check all wiring to be sure it is connected.
(b) Turn Mode Selector switch to the START position.
(c) Engine should crank and start. Return switch to RUN

position.

(d) When engine has come up to speed and governor has

Figure 4-4.1.2

No. of Gear Teeth x RPM set points

60

Set point

frequency in HZ

Pulley ratio x No. of Alternator Poles x RPM set points

60

Set point

frequency in HZ

=

=

OR

Function

Standard

Setting

Adjustment

Range

Adjustment

Type

Crank Time

15

seconds

10, 15, 20, 25

and 30 Seconds

Switch

Overspeed

3894 Hz

300 to 10 KHz

Pot. 500 Hz per

turn CW to increase

Lockout
for Start

SW1, SW2

Closed

SW3, 4, 5, 6

Open

Switch–

Table 4-4.1

Fuel Relay

Torque
Scews to
12 In./lb.

15

26

04

27

28

04

29

30

31

32

33

34

Crank

SW1 = 10 s.
SW2 = 15 s.
SW3 = 20 s.
SW4 = 25 s.
SW5 = 30 s.

Close Only One

Overspeed Overspeed

Time

Crank Relay

CLOSE

PUSH

OPEN

Pickup

Present

Test

Shutdown

Relay

Lockout

for start T.D.

102N34567102N345

Overspeed

Set

SW1 = Oil Pr
SW2 = Wt Tem
SW3 = Spare #1
SW4 = Spare #2
SW5 = Spare #3
SW6 = Spare #4

Overspeed

Relay

Torque

Scews to

12 In./lb.

35

36

37

38

39

40

41

42

43

44

45

46

40-05-0416

8

been adjusted for proper running speed, turn Mode
Selector switch OFF.

(e) All lights on the back of the MC-900 should go off and

the engine stop. If engine does not stop, check run
solenoid to be sure it has returned to the stop position.

4-4.3 Overspeed Switch Setting; To set the speed switch,
proceed as follows:

(a) Turn Mode Selector switch to the START position.
(b) Engine should crank and start. Return switch to RUN

position.

(c) With engine running, adjust governor to bring engine

speed to normal RPM.
(d) Depress and hold the Overspeed Test pushbutton.
(e) Slowly turn the Overspeed Set adjustment counter-

clockwise until the “Overspeed” and “Overspeed Relay”

lights on the MC-900 come on and the engine shuts

down.
(f) Release pushbutton; check “Overspeed” light on front

panel to be sure it is on.
(g) Turn Mode Selector switch OFF to reset shutdown

circuits.
(h) Restart engine, when engine starts, increase governor

speed setting slowly until engine shuts down on

overspeed. This should occur about 10% above

governor speed.
(i) Turn Mode Selector switch OFF.

4-4.4 Overcrank setting; to test the time before system shuts
down on overcrank;

(a) Disconnect the run solenoid wire from terminal 6 of the

Relay Module.
(b) Check time set on the “Crank Time” switch on MC-900

back panel. It is factory set at 15.
(c) Turn Mode Selector switch to START.

1. Engine will crank for 15 seconds.

2. After 15 seconds the “Overcrank” light on the MC­900 will come on and engine will stop cranking.

(d) Turn Mode Selector switch OFF.
(e) Reconnect the run solenoid wire at terminal 6 of the

Relay Module.

4-4.5 Oil Pressure; to test oil pressure shutdown circuit:

(a) Turn Mode Selector switch to START. When engine

starts, wait 30 seconds then,
(b) Use a jumper wire and short from terminal 28 to 4.
(c) ”Oil Pressure” light will come on and engine will stop.
(d) Turn Mode Selector switch OFF.

4-4.6 Water Temperature; to test the water temperature
shutdown circuit:

(a) Turn Mode Selector switch to START. When engine

starts, wait 30 seconds then,
(b) Use a jumper wire and short from terminal 29 to 4.
(c) “Water Temperature” light will come on and engine will

stop.
(d) Turn Mode Selector switch OFF.

4-4.7 All other Shutdowns; all other shutdowns would be
tested in the same manner.

(a) For shutdown circuits which are locked out by the

Shutdown Time Delay Bypass, you must wait 30

seconds before running the test.
(b) Circuits that are not locked out may be tested as soon as

the engine is running or may be tested without starting

the engine by turning the Mode Selector switch to RUN
position.

(c) To test other shutdowns, a jumper wire can be used to short

the input terminal for that circuit, to ground, terminal 4.

Section 5: Operation

5-1 Operator Controls.
5-1.1 Mode Selector Switch; allows the operator to start the

engine (START), run the engine (RUN), or stop the engine
(OFF).
5-1.2 The OFF position on the mode selector also provides a
reset function for the shutdown circuits. If the engine is shut
down by the automatic control, the operator must turn selector
off and back on to reactivate the system.
5-1.3 Push to Test Lamps; this pushbutton tests the shutdown
indicator lights.

5-2 Operating Modes.
5-2.1 The MC-900 Generator Engine Control has only one

operating mode: manual start and automatic shutdown on a
sensed failure of one of the monitored inputs.
5-2.2 Manual electric start is provided for operation of the
generator set.
5-2.2.1 To initiate Manual start, place the Mode Selector
switch in the START position. This provides a start signal to
the engine starter.
5-2.2.2 When engine starts, return selector switch to RUN.
This removes start signal and the engine will run.
5-2.3 OFF or Not Operating; to prevent operation of the
engine, turn selector switch OFF.
5-2.3.1 The OFF position is used as a reset for any automatic
shutdown that occurs.

Section 6: Routine Maintenance

and Operational Tests

6-1 Routine Maintenance.
6-1.1 Due to the design and types of components used, very

little maintenance is required to the MC-900 Control.
6-1.2 Visual inspection of the internal wiring of the control
panel, along with checking wire connections for tightness,
should be done on a semiannual schedule for stand- by systems
or quarterly for prime power. Check wire bundles for chafing
and wear to the insulation of the wires where they contact the
panel or engine.
6-1.4 Shutdown Circuits should be tested on a monthly basis
for prime power and quarterly for stand-by sets. The same
tests run during pre-operation check out, Section 4-4, should
be included.

6-2 Operational Tests.
6-2.1 No special operational tests are required. The routine

operational tests for the generator set will exercise the control.

Section 7: Troubleshooting and Repair

7-1 Tools Required.
7-1.1 Some of the tools necessary for troubleshooting are built

into the MC-900 Series controls.
7-1.1.1 By observing the lights on the front and rear of the
control panel, clues to a problem and the possible source can
be seen.

7-1.2 Other tools which may be required are:
7-1.2.l AC/DC Voltmeter for taking voltage readings and an

Ohmmeter for testing resistance of wires and connections.
7-1.2.2 Jumper wires with alligator clips to bypass or simulate
circuit closures.
DO NOT USE THESE JUMPER WIRES TO CHECK IF
VOLTAGE IS PRESENT AT A TERMINAL BY DRAWING
AN ARC TO GROUND. THIS WILL DAMAGE OR
DESTROY EQUIPMENT IN THE MC-900 CONTROL
PANEL.

7-2 MC-900 SELECTRONIC®Control Operation and

Shutdown.

7-2.1 The first step in troubleshooting any equipment is to

understand its normal operation. Table 7-2.1 contains normal
voltage readings taken at the terminals of the MC-900 with all
equipment shown on the standard drawing, connected.

(a) All voltage readings are DC, except at terminal 27, and

were taken with the negative lead of the meter connected
to ground at terminal 4. Voltage reading at terminal 27
was taken with negative lead grounded and the meter on
AC scale.

(b) The battery voltage, at the time readings were recorded,

was 13.8V and 27.6V. All readings will vary depending
on battery voltage, equipment supplied in the panel and
external devices connected to the MC-900 control. See
notes to the table for examples.

(c) Voltages less than battery also may vary due to

tolerances of the electronic components in the MC-900.
Minor variations, 1 or 2 volts, normally will have no
effect on the MC-900 operation.

(d) The AC voltage at terminal 27 must be a minimum of 2

VAC to drive the speed sensing circuits of the MC-900.

7-2.2 With power applied and the Mode Selector switch in
OFF, the following occurs when the switch is moved to the
START position.
7-2.2.1 The fuel relay is energized, which opens the circuits at
terminal 5 and 7, and closes the circuits at terminal 6 and 9.
This applies battery power to the run solenoid and to the
exciter terminal of the alternator (if used).
7-2.2.2 At the same time, the crank relay driver provides
battery voltage at terminal 16 to the auxiliary starter solenoid.
This output is controlled by the Mode Selector switch and the
Overcrank timer. The output will remain on until the Mode
Selector switch is returned to RUN or the Overcrank time
expires.
7-2.2.3 If the engine does not start during the Overcrank time,
the overcrank shutdown circuit trips and removes the output to
the starter solenoid. The Mode Selector switch must be turned
OFF to reset the shutdown circuit.
7-2.2.4 When the engine starts and the Mode Selector switch
is returned to the RUN position,

(a) Cranking is terminated.
(b) A time delay starts timing during which the oil pressure

and water temperature shutdown circuits are locked out.
(c) The overcrank timer is reset to zero.
(d) The overspeed shutdown circuit is activated.

7-2.2.5 An engine run signal closes to ground at terminal 17
when the Mode Selector switch is in the RUN position and the
engine is not shutdown by the MC-900 shutdown circuits.

7-2.3 With the Mode Selector switch in the RUN position, six of
the eight shutdown TATTLETALE®circuits are activated and
will operate anytime a switch closes from ground to their inputs.

Circuit Input Output

(a) Oil Pressure Terminal 28 Terminal 37
(b) Water Temp Terminal 29 Terminal 38
(c) Overspeed* Int. Speed Switch Terminal 36
(d) Overcrank** Int. Circuit Terminal 35
(e) Spare Shutdown #1 Terminal 30 Terminal 39
(f) Spare Shutdown #2 Terminal 31 Terminal 40
(g) Spare Shutdown #3 Terminal 32 Terminal 43
(h) Spare Shutdown #4 Terminal 30 Terminal 44

*Engine must be running to operate speed switch

**Circuit operates only while cranking

7-2.3.1 Each circuit has a indicating light and a transistor
output that closes to ground to operate an individual remote
indicating light.
7-2.3.2 When any of the eight shutdown functions trip, the
shutdown relay K-2, pulls in and applies battery power to
terminal 10. At the same time, the fuel relay, K-1 drops out
and if the shutdown was due to overspeed, the overspeed relay,
K-3 pulls in to signal an air shut off solenoid, terminal 11 to
close.
7-2.3.3 The eight shutdown circuits, paragraph 7-2.3, are first
out latching type TATTLETALES®. That is, only one of the
eight may trip at one time and it must be reset before the MC­900 will operate again.
7-2.3.4 If one of the TATTLETALE®circuits trip, the
following occurs to shutdown the engine and generator.

(a) The TATTLETALE®light for that function turns on.
(b) Shutdown relay K-2 is energized, closing its contacts at

terminal 10. These contacts can be wired to a shunt trip
solenoid in the generator circuit breaker if required.

(c) The fuel relay drops out, removing battery voltage from

the run solenoid, terminal 6. The circuit at terminal 5
will close to reconnect the battery positive to this

terminal.
(d) The run signal, terminal 17 turns off.
(e) If the shutdown is due to overspeed, the overspeed relay

operates and applies battery positive to terminal 11 to

close an air shutoff solenoid if the engine is so equipped.

7-2.3.5 The dry contacts of relay K-1, at terminals 7, 8 and 9;
relay K-2, at terminals 18, 19 and 20; and relay K-3, at
terminals 20, 21 and 22; change state when the relays operate.
7-2.3.6 To reset the circuits, the Mode Selector switch must be
turned OFF.

7-2.4 Normally, the engine will run until the Mode Selector
switch is turned OFF.
7-2.4.1 When this happens, the following occurs to stop the
engine;

(a) The fuel relay drops out, removing battery voltage from

the run solenoid. The circuit at terminal 5 will close to

reconnect the battery positive to this terminal.
(b) The run signal, terminal 17 turns off.
(c) The TATTLETALE®circuits are locked out as soon as

the switch is turned OFF. This prevents any

TATTLETALE®from tripping while the engine coasts to

a stop.

9

Input

13.8

Voltage

27.6

Input

13.8

Voltage

27.6

Input

13.8

Voltage

27.6

Input

13.8

Voltage

27.6

10

1 13.8 27.6 13.8 27.6 13.8 27.6 13.8 27.6
4 00000 0 00
5 13.8 27.6 0 0 0 0 13.8 27.6
6 0 0 13.8 27.6 13.8 27.6 0 0
7 00000 0 00
8 00000 0 00
9 00000 0 00
10 0 0 0 0 0 0 13.8 27.6
11 00000000
12 00000000
13 00000000
14 00000000
15 13.8 27.6 13.8 27.6 13.8 27.6 13.8 27.6
16 0 0 13.8 27.6 0 0 0 0
17 00000000
18 00000000
19 00000000
20 00000000
21 00000000
22 00000000
23 00000000
24 00000000
25 00000000
26 13.8 27.6 0 0 0 0 13.8 27.6
27 (1) 0 0 4 4 4 4 0 0
28 (2) 0 0 0 0 7.5 7.5 0 0
29 0 0 7.5 7.5 7.5 7.5 7.5 7.5
30 0 0 7.5 7.5 7.5 7.5 7.5 7.5
31 0 0 7.5 7.5 7.5 7.5 7.5 7.5
32 0 0 7.5 7.5 7.5 7.5 7.5 7.5
33 0 0 7.5 7.5 7.5 7.5 7.5 7.5
34 00000000
35 13.8 27.6 13.8 27.6 13.8 27.6 13.8 27.6
36 13.8 27.6 13.8 27.6 13.8 27.6 13.8 27.6
37 (2) 13.8 27.6 13.8 27.6 13.8 27.6 0 0
38 13.8 27.6 13.8 27.6 13.8 27.6 13.8 27.6
39 13.8 27.6 13.8 27.6 13.8 27.6 13.8 27.6
40 13.8 27.6 13.8 27.6 13.8 27.6 13.8 27.6
41 00000000
42 00000000
43 13.8 27.6 13.8 27.6 13.8 27.6 13.8 27.6
44 13.8 27.6 13.8 27.6 13.8 27.6 13.8 27.6
45 00000000
46 00000000

NOTES

Note 1: AC voltage measured on AC scale of volt-ohmmeter.
Note 2: Low Oil Pressure shutdown circuit.

Oil pressure was the cause of shutdown on column 4.

Table 7-2.1

Mode

Selector

OFF

Mode Selector

START

Cranking

Mode Selector

RUN

Running

Mode Selector

RUN

Shutdown

Terminal

Number

Section 8: Replacement Parts

8-1 Replacement Parts
8-1.1 Table 8-1 covers all of the replaceable components of

the MC-900 Series Generator Engine Controls. The part
numbers shown are Frank W. Murphy Mfr. part numbers and
may not appear on the individual parts.
8-1.2 Each complete control is made up of a Control / Display
Module, a Relay Module and a number of Relays.
8-1.3 There are no field replaceable parts in the Control /
Display Module, the complete module must be replaced if it
fails. All relays are individually replaceable in the Relay
Module but the module must be replaced if a failure of the
circuit board occurs.

8-2 Replacement Parts Waukesha Modules
8-2.1 Table 8-2 part numbers are Murphy part numbers for

MC-900 controls manufactured for Waukesha Corporation.
These OEM parts are available only to Waukesha and their
distributors.
8-2.2 The MC-900 parts are the same as the Murphy MC-900
series that has been covered through out this manual.

11

Model Number

MC-900-12
MC-900-24
MC-900-2-24

Part Number

40-70-0130
40-70-0177
40-70-0173

Control / Display

40-00-0023
40-00-0023
40-00-0023

Relay Module

40-00-0091
40-00-0091
40-00-0091

Relay Part

00-00-2952
00-00-2953
00-00-2953

Relay Qty. Module

2
2
3

Model Number

MC-900-2-24
Waukesha

Part Number

40-35-0047

Control / Display

40-00-0223

Relay Module

40-00-0224

Relay Part

00-00-2953

Relay Qty. Module

2

Table 8-1

Table 8-2

CONTROL SYSTEMS & SERVICES DIVISION

P.O. Box 1819; Rosenberg, Texas 77471; USA
[phone] fax [phone]

e-mail [e-mail]

MURPHY DE MEXICO, S.A. DE C.V.

Blvd. Antonio Rocha Cordero 300, Fracción del Aguaje
San Luis Potosí, S.L.P.; México 78384
[phone] fax [phone]
Villahermosa Office [phone]
e-mail [e-mail]
www.murphymex.com.mx

FRANK W. MURPHY, LTD.

Church Rd.; Laverstock, Salisbury SP1 1QZ; U.K.
[phone] fax [phone]
e-mail [e-mail]
www.fwmurphy.co.uk

MURPHY SWITCH OF CALIFORNIA

41343 12th Street West
Palmdale, California 93551-1442; USA
[phone] fax [phone]
e-mail [e-mail]
www.murcal.com

In order to consistently bring you the highest quality, full featured products, we reserve the right to change our specifications and designs at any time.

MACQUARRIE CORPORATION

1620 Hume Highway
Campbellfield, Vic 3061; Australia
[phone] fax [phone]
e-mail [e-mail]

FW Murphy

P.O. Box 470248
Tulsa, Oklahoma 74147 USA
[phone]

fax [phone]
e-mail [e-mail]

www.fwmurphy.com

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