Guardian Technologies 4759, 4758, 4760, 4390, 4389 User Manual

Models:
4389, 4758 (6 kW NG, 7 kW LP)
4456, 4759 (12 kW NG, 12 kW LP)
4390, 4760 (13 kW, 15 kW LP)

DIAGNOSTIC
REPAIR MANUAL

AUTOMATIC HOME STANDBY GENERATORS

Visit us online at

www.guardiangenerators.com

DIAGNOSTIC
REPAIR MANUAL

AIR-COOLED

PART TITLE

Specifications
1 General Information
2 AC Generators
3 V-Type Prepackaged Transfer Switches
4 DC Control
5 Operational Tests and Adjustments
6 Disassembly
7 Electrical Data

DIAGNOSTIC

REPAIR MANUAL

Air-cooled, Prepackaged

Automatic Standby

Generators

Models:

04389, 04758 (6 kW NG, 7 kW LP)
04456, 04759 (12 kW NG, 12 kW LP)
04390, 04760 (13 kW NG, 15 kW LP)

TABLE OF CONTENTS

TO FIND KNOWN VALUES 1-PHASE 3-PHASE

KILOWATTS (kW) Volts, Current, Power Factor E x I

E x I x 1.73 x PF

1000 1000

KVA Volts, Current E x I E x I x 1.73

1000 1000

AMPERES kW, Volts, Power Factor kW x 1000 kW x 1000

E E x 1.73 x PF

WATTS Volts, Amps, Power Factor Volts x Amps E x I x 1.73 x PF

NO. OF ROTOR Frequency, RPM 2 x 60 x Frequency 2 x 60 x frequency
POLES RPM RPM

FREQUENCY RPM, No. of Rotor Poles RPM x Poles RPM x Poles

2 x 60 2 x 60

RPM Frequency, No. of Rotor Poles 2 x 60 x Frequency

2 x 60 x Frequency

Rotor Poles Rotor Poles

kW (required for Motor Horsepower, Efficiency HP x 0.746 HP x 0.746
Motor) Efficiency Efficiency

RESISTANCE Volts, Amperes E E

II

VOLTS Ohm, Amperes I x R I x R

AMPERES Ohms, Volts E E

RR

E = VOLTS I = AMPERES R = RESISTANCE (OHMS) PF = POWER FACTOR

ELECTRICAL FORMULAS

Page 1

SPECIFICATIONS

Page 2

GENERATOR

Models 04389, 04758 Models 04456, 04759 Model 04390, 04760

Rated Max. Continuous Power Capacity (Watts*) 6,000 NG/7,000 LP 12,000 NG/12,000 LP 13,000 NG/15,000 LP
Rated Voltage 120/240 120/240 120/240
Rated Max. Continuous Load Current (Amps)

120 Volts** 50.0 NG/58.3 LP 100.0 NG/100.0 LP 108.3 NG/125.0 LP

240 Volts 25.0 NG/29.2 LP 50.0 NG/50.0 LP 54.2 NG/62.5 LP
Main Line Circuit Breaker 30 Amp 50 Amp 60 Amp/70 Amp
Phase 1 1 1
Number of Rotor Poles 2 2 2
Rated AC Frequency 60 Hz 60 Hz 60 Hz
Power Factor 1 1 1
Battery Requirement Group 26/26R Group 26/26R Group 26/26R

12 Volts and 12 Volts and 12 Volts and

350 Cold-cranking 550 Cold-cranking 550 Cold-cranking

Amperes Minimum Amperes Minimum Amperes Minimum
Weight 452 Pounds 470 Pounds 487 Pounds
Output Sound Level @ 23 ft (7m) at full load 68 db (A) 70.5db (A) 71.5 db (A)
Normal Operating Range -20 F (-28.8 C) to 104 F (40 C)

* Maximum wattage and current are subject to and limited by such factors as fuel Btu content, ambient temperature, altitude, engine power and condition, etc. Maximum power

decreases about 3.5 percent for each 1,000 feet above sea level; and also will decrease about 1 percent for each 6 C (10 F) above 16 C (60 F) ambient temperature.

** Load current values shown for 120 volts are maximum TOTAL values for two separate circuits. The maximum current in each circuit must not exceed the value stated for 240 volts.

15,000 watt with upgrade kit 04578-0. Kit includes power harnesses and 70 amp 2-pole circuit breaker.

ENGINE

Models 04389, 04758 Models 04456, 04759 Models 04390, 04760

Type of Engine GH-410 GT-990 GT-990
Number of Cylinders 1 2 2
Rated Horsepower 14.5 @ 3,600 rpm 26 @ 3,600 rpm 30 @ 3,600 rpm
Displacement 410cc 992cc 992cc
Cylinder Block Aluminum w/Cast Aluminum w/Cast Aluminum w/Cast

Iron Sleeve Iron Sleeve Iron Sleeve
Valve Arrangement Overhead Valves Overhead Valves Overhead Valves
Ignition System Solid-state w/Magneto Solid-state w/Magneto Solid-state w/Magneto
Recommended Spark Plug RC12YC RC12YC RC12YC
Spark Plug Gap 0.76 mm (0.030 inch) 0.5 mm (0.020 inch) 0.5 mm (0.020 inch)
Compression Ratio 8.6:1 9.5:1 9.5:1
Starter 12 Vdc 12 Vdc 12Vdc
Oil Capacity Including Filter Approx. 1.5 Qts Approx. 1.7 Qts Approx. 1.7 Qts
Recommended Oil Filter Generac Part # 070185 Generac Part # 070185 Generac Part # 070185
Recommended Air Filter Generac Part # 0C8127 Generac Part # 0C8127 Generac Part # 0C8127
Operating RPM 3,600 3,600 3,600

FUEL CONSUMPTION

Model # Natural Gas* LP Vapor**

1/2 Load Full Load 1/2 Load Full Load

04389, 04758 74 105 0.91/33 1.21/44.1
04556, 04759 114 185 1.34/48.9 2.17/79.0
04390, 04760 148.5 240 1.73/63.2 2.80/102.3

* Natural gass is in cubic feet per hour. **LP is in gallons per hour/cubic feet per hour.

STATOR WINDING RESISTANCE VALUES / ROTOR RESISTANCE

Model 04692 Models 04389 Models 04456 Models 04390

04679, 04758 04759 04760

Power Winding: Across 11 & 22 0.190-0.208 ohms 0.223-0.259 ohms 0.115 ohms 0.08/0.08 ohms
Power Winding: Across 33 & 44 0.190-0.208 ohms 0.223-0.259 ohms 0.115 ohms 0.08/0.08 ohms
Excitation Winding: Across 2 & 6 1.442-1.670 ohms 1.53-1.77 ohms 0.745 ohms 0.705 ohms
Engine Run Winding: Across 55 & 66A 0.104-0.120 ohms 0.100-0.169 ohms 0.109 ohms 0.087 ohms
Battery Charge Winding: Across 66 & 77 0.137-0.158 ohms 0.146-0.169 ohms 0.164 ohms 0.130 ohms
Rotor Resistance 15.42-17-85 ohms 11.88-13.76 ohms 15.9 ohms 19.8 ohms

Page 3

SPECIFICATIONS

MOUNTING DIMENSIONS

Page 4

SPECIFICATIONS

MOUNTING DIMENSIONS

SPECIFICATIONS

Page 5

MAJOR FEATURES

12 kW and 15 kW, V-twin GT-990 Engine

7 kW, Single Cylinder GH-410 Engine

PART TITLE

1.1 Generator Identification

1.2 Prepackaged Installation Basics

1.3 Preparation Before Use

1.4 Testing, Cleaning and Drying

1.5 Engine-Generator Protective Devices

1.6 Operating Instructions

1.7 Automatic Operating Parameters

PART 1

GENERAL

INFORMATION

Air-cooled, Prepackaged

Automatic Standby Generators

Models:

04389, 04758 (6 kW NG, 7 kW LP)
04456, 04759 (12 kW NG, 12 kW LP)
04390, 04760 (13 kW NG, 15 kW LP)

TABLE OF CONTENTS

SECTION 1.1

GENERATOR IDENTIFICATION

GENERAL INFORMATION

PART 1

Page 1.1-1

INTRODUCTION

This Diagnostic Repair Manual has been prepared
especially for the purpose of familiarizing service
personnel with the testing, troubleshooting and repair
of air-cooled, prepackaged automatic standby
generators. Every effort has been expended to
ensure that information and instructions in the manual
are both accurate and current. However, Generac
reserves the right to change, alter or otherwise
improve the product at any time without prior
notification.

The manual has been divided into ten PARTS. Each
PART has been divided into SECTIONS. Each
SECTION consists of two or more SUBSECTIONS.

It is not our intent to provide detailed disassembly and
reassemble instructions in this manual. It is our intent
to (a) provide the service technician with an
understanding of how the various assemblies and
systems work, (b) assist the technician in finding the
cause of malfunctions, and (c) effect the expeditious
repair of the equipment.

ITEM NUMBER:

Many home standby generators are manufactured to
the unique specifications of the buyer. The Model
Number identifies the specific generator set and its
unique design specifications.

SERIAL NUMBER:

Used for warranty tracking purposes.

Figure 1. A Typical Data Plate

SECTION 1.2

PREPACKAGED INSTALLATION BASICS

GENERAL INFORMATION

INTRODUCTION

Information in this section is provided so that the
service technician will have a basic knowledge of
installation requirements for prepackaged home
standby systems. Problems that arise are often
related to poor or unauthorized installation practices.

A typical prepackaged home standby electric system
is shown in Figure 1 (next page). Installation of such a
system includes the following:

❏Selecting a Location
❏Grounding the generator.
❏Providing a fuel supply.
❏Mounting the load center.
❏Connecting power source and load lines.
❏Connecting system control wiring.
❏Post installation tests and adjustments.

SELECTING A LOCATION

Install the generator set as close as possible to the
electrical load distribution panel(s) that will be powered
by the unit, ensuring that there is proper ventilation for
cooling air and exhaust gases. This will reduce wiring
and conduit lengths. Wiring and conduit not only add to
the cost of the installation, but excessively long wiring
runs can result in a voltage drop.

GROUNDING THE GENERATOR

The National Electric Code requires that the frame
and external electrically conductive parts of the
generator be property connected to an approved
earth ground. Local electrical codes may also require
proper grounding of the unit. For that purpose, a
grounding lug is attached to the unit. Grounding may
be accomplished by attaching a stranded copper wire
of the proper size to the generator grounding lug and
to an earth-driven copper or brass grounding-rod
(electrode). Consult with a local electrician for
grounding requirements in your area.

THE FUEL SUPPLY

Prepackaged units with air-cooled engine were
operated, tested and adjusted at the factory using
natural gas as a fuel. These air-cooled engine units can be

converted to use LP (propane) gas by making a few
adjustments for best operation and power.

LP (propane) gas is usually supplied as a liquid in
pressure tanks. Both the air-cooled and the liquid
cooled units require a "vapor withdrawal" type of fuel
supply system when LP (propane) gas is used. The
vapor withdrawal system utilizes the gaseous fuel
vapors that form at the top of the supply tank.

The pressure at which LP gas is delivered to the
generator fuel solenoid valve may vary considerably,
depending on ambient temperatures. In cold weather,
supply pressures may drop to "zero". In warm
weather, extremely high gas pressures may be
encountered. A primary regulator is required to
maintain correct gas supply pressures.

Recommended gaseous fuel pressure at the inlet side
of the generator fuel solenoid valve is (a) a minimum
of 11 inches water column (6.38 ounces per square
inch), and (b) a maximum of 14 inches water column
(8 ounces per square inch). A primary regulator is
required to ensure that proper fuel supply pressures
are maintained.

DANGER: LP AND NATURAL GAS ARE BOTH
HIGHLY EXPLOSIVE. GASEOUS FUEL LINES
MUST BE PROPERLY PURGED AND TESTED
FOR LEAKS BEFORE THIS EQUIPMENT IS
PLACED INTO SERVICE AND PERIODICALLY
THEREAFTER. PROCEDURES USED IN
GASEOUS FUEL LEAKAGE TESTS MUST
COMPLY STRICTLY WITH APPLICABLE FUEL
GAS CODES. DO NOT USE FLAME OR ANY
SOURCE OF HEAT TO TEST FOR GAS
LEAKS. NO GAS LEAKAGE IS PERMITTED.
LP GAS IS HEAVIER THAN AIR AND TENDS
TO SETTLE IN LOW AREAS. NATURAL GAS
IS LIGHTER THAN AIR AND TENDS TO
SETTLE IN HIGH PLACES. EVEN THE
SLIGHTEST SPARK CAN IGNITE THESE
FUELS AND CAUSE AN EXPLOSION.

Use of a flexible length of hose between the
generator fuel line connection and rigid fuel lines is
required. This will help prevent line breakage that
might be caused by vibration or if the generator shifts
or settles. The flexible fuel line must be approved for
use with gaseous fuels.

Flexible fuel line should be kept as straight as
possible between connections. The bend radius for
flexible fuel line is nine (9) inches. Exceeding the
bend radius can cause the fittings to crack.

THE TRANSFER SWITCH / LOAD CENTER

A transfer switch is required by electrical code, to
prevent electrical feedback between the UTILITY and
STANDBY power sources, and to transfer electrical
loads from one power supply to another safely.

PREPACKAGED TRANSFER SWITCHES:
Instructions and information on prepackaged transfer

switches may be found in Part 3 of this manual.

PART 1

Page 1-2.1

PART 1

GENERAL INFORMATION

SECTION 1.2

PREPACKAGED INSTALLATION BASICS

Page 1.2-2

Figure 1. Typical Prepackaged Installation

SECTION 1.2

PREPACKAGED INSTALLATION BASICS

GENERAL INFORMATION

POWER SOURCE AND LOAD LINES

The utility power supply lines, the standby (generator)
supply lines, and electrical load lines must all be
connected to the proper terminal lugs in the transfer
switch. The following rules apply:In 1-phase systems
with a 2-pole transfer switch, connect the two utility
source hot lines to Transfer Switch Terminal Lugs N1
and N2. Connect the standby source hot lines (E1,
E2) to Transfer Switch Terminal Lugs E1 and E2.
Connect the load lines from Transfer Switch Terminal
Lugs T1 and T2 to the electrical load circuit. Connect
UTILITY, STANDBY and LOAD neutral lines to the

neutral block in the transfer switch.

SYSTEM CONTROL INTERCONNECTIONS

Prepackaged home standby generators are equipped
with a terminal board identified with the following
terminals: (a) UTILITY 1, (b) UTILITY 2, (c) 23, and (d)

194. Prepackaged load centers house an identically
marked terminal board. When these four terminals are
properly interconnected, dropout of utility source
voltage below a preset value will result in automatic
generator startup and transfer of electrical loads to the
"Standby" source. On restoration of utility source
voltage above a preset value will result in retransfer
back to that source and generator shutdown.

PART 1

Figure 2. Proper Fuel Installation

Page 1-2.3

PART 1

GENERAL INFORMATION

SECTION 1.3

PREPARATION BEFORE USE

GENERAL

The installer must ensure that the home standby
generator has been properly installed. The system
must be inspected carefully following installation. All
applicable codes, standards and regulations
pertaining to such installations must be strictly
complied with. In addition, regulations established by
the Occupational Safety and Health Administration
(OSHA) must be complied with.

Prior to initial startup of the unit, the installer must
ensure that the engine-generator has been properly
prepared for use. This includes the following:

❏An adequate supply of the correct fuel must be

available for generator operation.

❏The engine must be properly serviced with the

recommended oil.

FUEL REQUIREMENTS

Generators with air-cooled engine have been factory
tested and adjusted using natural gas as a fuel. If LP
(propane) gas is to be used at the installation site,
adjustment of the generator fuel regulator will be
required for best performance. Refer to Test 63,
"Check Fuel Regulator" on Page 4.4-16 for fuel
regulator adjustment procedures.

❏When natural gas is used as a fuel, it should be

rated at least 1000 BTU’s per cubic foot.

❏When LP (propane) gas is used as a fuel, it should

be rated at 2520 BTU’s per cubic foot.

ENGINE OIL RECOMMENDATIONS

The primary recommended oil for units with air-cooled,
single cylinder or V-Twin engines is synthetic oil.
Synthetic oil provides easier starts in cold weather and
maximum engine protection in hot weather. Use high
quality detergent oil that meets or exceeds API
(American Petroleum Institute) Service class SG, SH,
or SJ requirements for gasoline engines. The following
chart lists recommended viscosity ranges for the lowest
anticipated ambient temperatures.

Engine crankcase oil capacities for the engines
covered in this manual can be found in the
specifications section at the beginning of the book.

LOWEST ANTICIPATED AIR COOLED ENGINE
AMBIENT TEMPERATURE RECOMMENDED OIL

Above 60 F. (16 C.) Use SAE 30 oil
20 -59 F. (-7 to 15 C.) Use SAE 10W-30 oil
Below 20 F. (-7 C.) SAE 5W-20/5W-30 oil
For all seasons Use SAE 5W-30

Synthetic oil

Page 1.3-1

SECTION 1.4

TESTING, CLEANING AND DRYING

GENERAL INFORMATION

VISUAL INSPECTION

When it becomes necessary to test or troubleshoot a
generator, it is a good practice to complete a
thorough visual inspection. Remove the access
covers and look closely for any obvious problems.
Look for the following:

❏Burned or broken wires, broken wire connectors,

damaged mounting brackets, etc.

❏Loose or frayed wiring insulation, loose or dirty

connections.

❏Check that all wiring is well clear of rotating parts.
❏Verify that the Generator properly connected for the

correct rated voltage. This is especially important
on new installations. See Section 1.2, "AC
Connection Systems".

❏Look for foreign objects, loose nuts, bolts and other

fasteners.

❏Clean the area around the Generator. Clear away

paper, leaves, snow, and other objects that might
blow against the generator and obstruct its air
openings.

METERS

Devices used to measure electrical properties are
called meters. Meters are available that allow one to
measure (a) AC voltage, (b) DC voltage, (c) AC
frequency, and (d) resistance In ohms. The following
apply:

❏To measure AC voltage, use an AC voltmeter.
❏To measure DC voltage, use a DC voltmeter.
❏Use a frequency meter to measure AC frequency In

"Hertz" or "cycles per second".

❏Use an ohmmeter to read circuit resistance, in "ohms".

THE VOM

A meter that will permit both voltage and resistance to
be read is the "volt-ohm-milliammeter" or "VOM".

Some VOM’s are of the analog type (not shown).
These meters display the value being measured by
physically deflecting a needle across a graduated
scale. The scale used must be interpreted by the user.

Digital VOM’s (Figure 1) are also available and are
generally very accurate. Digital meters display the
measured values directly by converting the values to
numbers.

NOTE: Standard AC voltmeters react to the
AVERAGE value of alternating current. When working
with AC, the effective value is used. For that reason a
different scale is used on an AC voltmeter. The scale
is marked with the effective or "rms" value even
though the meter actually reacts to the average value.
That is why the AC voltmeter will give an Incorrect
reading if used to measure direct current (DC).

Figure 1. Digital VOM

MEASURING AC VOLTAGE

An accurate AC voltmeter or a VOM may be used to
read the generator AC output voltage. The following
apply:

1. Always read the generator AC output voltage only at the
unit's rated operating speed and AC frequency.

2. The generator voltage regulator can be adjusted for
correct output voltage only while the unit is operating at
its correct rated speed and frequency.

3. Only an AC voltmeter may be used to measure AC
voltage. DO NOT USE A DC VOLTMETER FOR THIS
PURPOSE.

DANGER!: GENERATORS PRODUCE HIGH
AND DANGEROUS VOLTAGES. CONTACT
WITH HIGH VOLTAGE TERMINALS WILL
RESULT IN DANGEROUS AND POSSIBLY
LETHAL ELECTRICAL SHOCK.

MEASURING DC VOLTAGE

A DC voltmeter or a VOM may be used to measure
DC voltages. Always observe the following rules:

1. Always observe correct DC polarity.

a. Some VOM’s may be equipped with a

polarity switch.

b. On meters that do not have a polarity

switch, DC polarity must be reversed by
reversing the test leads.

PART 1

Page 1.4-1

SECTION 1.4

TESTING, CLEANING AND DRYING

PART 1

GENERAL INFORMATION

2. Before reading a DC voltage, always set the meter to a
higher voltage scale than the anticipated reading. if in
doubt, start at the highest scale and adjust the scale
downward until correct readings are obtained.

3. The design of some meters is based on the "current flow"

theory while others are based on the "electron flow" theory.

a. The "current flow" theory assumes that

direct current flows from the positive (+) to
the negative (-).

b. The "electron flow" theory assumes that

current flows from negative (-) to positive
(+).

NOTE: When testing generators, the "current flow"
theory is applied. That is, current is assumed to flow
from positive (+) to negative (-)).

MEASURING AC FREQUENCY

The generator AC output frequency is proportional to
rotor speed. Generators equipped with a 2-pole rotor
must operate at 3600 rpm to supply a frequency of 60
Hertz. Units with 4-pole rotor must run at 1800 rpm to
deliver 60 Hertz.

Correct engine and rotor speed is maintained by an
engine speed governor. For models rated 60 Hertz,
the governor is generally set to maintain a no-load
frequency of about 62 Hertz with a corresponding
output voltage of about 124 volts AC line-to-neutral.
Engine speed and frequency at no-load are set
slightly high to prevent excessive rpm and frequency
droop under heavy electrical loading.

MEASURING CURRENT

To read the current flow, in AMPERES, a clamp-on
ammeter may be used. This type of meter indicates
current flow through a conductor by measuring the
strength of the magnetic field around that conductor.
The meter consists essentially of a current
transformer with a split core and a rectifier type
instrument connected to the secondary. The primary
of the current transformer is the conductor through
which the current to be measured flows. The split
core allows the Instrument to be clamped around the
conductor without disconnecting it.

Current flowing through a conductor may be
measured safely and easily. A line-splitter can be
used to measure current in a cord without separating
the conductors.

Figure 2. Clamp-On Ammeter

Figure 3. A Line-Splitter

NOTE: If the physical size of the conductor or
ammeter capacity does not permit all lines to be
measured simultaneously, measure current flow in
each individual line. Then, add the Individual
readings.

MEASURING RESISTANCE

The volt-ohm-milliammeter may be used to measure
the resistance in a circuit. Resistance values can be
very valuable when testing coils or windings, such as
the stator and rotor windings.

When testing stator windings, keep in mind that the
resistance of these windings is very low. Some
meters are not capable of reading such a low
resistance and will simply read CONTINUITY.

Page 1.4-2

SECTION 1.4

TESTING, CLEANING AND DRYING

GENERAL INFORMATION

If proper procedures are used, the following
conditions can be detected using a VOM:

❏A "short-to-ground" condition in any stator or rotor

winding.

❏Shorting together of any two parallel stator windings.
❏Shorting together of any two isolated stator windings.
❏An open condition in any stator or rotor winding.

Component testing may require a specific resistance
value or a test for INFINITY or CONTINUITY.
INFINITY is an OPEN condition between two
electrical points, which would read as no resistance
on a VOM. CONTINUITY is a CLOSED condition
between two electrical points, which would be
indicated as very low resistance or ZERO on a VOM.

ELECTRICAL UNITS

AMPERE:
The rate of electron flow in a circuit is represented by

the AMPERE. The ampere is the number of electrons
flowing past a given point at a given time. One
AMPERE is equal to just slightly more than six
thousand million billion electrons per second.

With alternating current (AC), the electrons flow first
in one direction, then reverse and move in the
opposite direction. They will repeat this cycle at
regular intervals. A wave diagram, called a "sine
wave" shows that current goes from zero to maximum
positive value, then reverses and goes from zero to
maximum negative value. Two reversals of current
flow is called a cycle. The number of cycles per
second is called frequency and is usually stated in
"Hertz".

VOLT:
The VOLT is the unit used to measure electrical

PRESSURE, or the difference in electrical potential
that causes electrons to flow. Very few electrons will
flow when voltage is weak. More electrons will flow as
voltage becomes stronger. VOLTAGE may be
considered to be a state of unbalance and current
flow as an attempt to regain balance. One volt is the
amount of EMF that will cause a current of 1 ampere
to flow through 1 ohm of resistance.

OHM:
The OHM is the unit of RESISTANCE. In every circuit

there is a natural resistance or opposition to the flow
of electrons. When an EMF is applied to a complete
circuit, the electrons are forced to flow in a single
direction rather than their free or orbiting pattern. The
resistance of a conductor depends on (a) its physical
makeup, (b) its cross-sectional area, (c) its length,
and (d) its temperature. As the conductor’s
temperature increases, its resistance increases in
direct proportion. One (1) ohm of resistance will
permit one (1) ampere of current to flow when one (1)
volt of electromotive force (EMF) is applied.

Figure 4. Electrical Units

OHM'S LAW

A definite and exact relationship exists between
VOLTS, OHMS and AMPERES. The value of one can
be calculated when the value of the other two are
known. Ohm’s Law states that in any circuit the current
will increase when voltage increases but resistance
remains the same, and current will decrease when
resistance Increases and voltage remains the same.

Figure 5.

If AMPERES is unknown while VOLTS and OHMS
are known, use the following formula:

AMPERES =

VOLTS

OHMS

If VOLTS is unknown while AMPERES and OHMS
are known, use the following formula:

VOLTS = AMPERES x OHMS

If OHMS is unknown but VOLTS and AMPERES are
known, use the following:

OHMS

=

VOLTS

AMPERES

PART 1

Page 1.4-3

SECTION 1.4

TESTING, CLEANING AND DRYING

PART 1

GENERAL INFORMATION

INSULATION RESISTANCE

The insulation resistance of stator and rotor windings
is a measurement of the integrity of the insulating
materials that separate the electrical windings from the
generator steel core. This resistance can degrade over
time or due to such contaminants as dust, dirt, oil,
grease and especially moisture. In most cases, failures
of stator and rotor windings is due to a breakdown in
the insulation. And, in many cases, a low insulation
resistance is caused by moisture that collects while the
generator is shut down. When problems are caused by
moisture buildup on the windings, they can usually be
corrected by drying the windings. Cleaning and drying
the windings can usually eliminate dirt and moisture
built up in the generator windings.

THE MEGOHMMETER

GENERAL:
A megohmmeter, often called a "megger", consists of

a meter calibrated in megohms and a power supply.
Use a power supply of 500 volts when testing stators
or rotors. DO NOT APPLY VOLTAGE LONGER
THAN ONE (1) SECOND.

TESTING STATOR INSULATION:
All parts that might be damaged by the high megger

voltages must be disconnected before testing. Isolate
all stator leads (Figure 2) and connect all of the stator
leads together. FOLLOW THE MEGGER
MANUFACTURER’S INSTRUCTIONS CAREFULLY.

Use a megger power setting of 500 volts. Connect
one megger test lead to the junction of all stator
leads, the other test lead to frame ground on the
stator can. Read the number of megohms on the
meter.

The MINIMUM acceptable megger reading for stators

may be calculated using the following formula:

EXAMPLE: Generator is rated at 120 volts AC. Divide
"120" by "1000" to obtain "0.12". Then add "1" to
obtain "1.12" megohms. Minimum Insulation
resistance for a 120 VAC stator is 1.12 megohms.

If the stator insulation resistance is less than the
calculated minimum resistance, clean and dry the
stator. Then, repeat the test. If resistance is still low,
replace the stator.

Use the Megger to test for shorts between isolated
windings as outlined "Stator Insulation Tests .

Also test between parallel windings. See "Test
Between Parallel Windings" on this page.

TESTING ROTOR INSULATION:
Apply a voltage of 500 volts across the rotor positive

(+) slip ring (nearest the rotor bearing), and a clean
frame ground (i.e. the rotor shaft). DO NOT EXCEED
500 VOLTS AND DO NOT APPLY VOLTAGE
LONGER THAN 1 SECOND. FOLLOW THE
MEGGER MANUFACTURER’S INSTRUCTIONS
CAREFULLY.

ROTOR MINIMUM INSULATION RESISTANCE:

1.5 megohms

CAUTION: Before attempting to measure
Insulation resistance, first disconnect and
Isolate all leads of the winding to be tested.
Electronic components, diodes, surge
protectors, relays, voltage regulators, etc., can
be destroyed if subjected to high megger
voltages.

HI-POT TESTER:
A "Hi-Pot" tester is shown in Figure 1. The model

shown is only one of many that are commercially
available. The tester shown is equipped with a
voltage selector switch that permits the power supply
voltage to be selected. It also mounts a breakdown
lamp that will illuminate to indicate an insulation
breakdown during the test.

Figure 1. One Type of Hi-Pot Tester

STATOR INSULATION RESISTANCE TEST

GENERAL:
Units with air-cooled engines are equipped with (a)

dual stator AC power windings, (b) an excitation or
DPE winding, (c) a battery charge winding and (d) an
engine run winding. Insulation tests of the stator
consist of (a) testing all windings to ground, (b) testing
between isolated windings, and (c) testing between
parallel windings. Figure 2 is a pictorial representation
of the various stator leads on units with air-cooled
engine.

Page 1.4-4

MINIMUM INSULATION

GENERATOR RATED VOLTS

RESISTANCE =

__________________________

+1

(in "Megohms")

1000

SECTION 1.4

TESTING, CLEANING AND DRYING

GENERAL INFORMATION

PART 1

TESTING ALL STATOR WINDINGS TO GROUND:

1. Disconnect stator output leads 11 and 44 from the
generator main line circuit breaker.

2. Remove stator output leads 22 and 33 from the neutral
connection and separate the two leads.

3. Disconnect C2 connector from the side of the control
panel. The C2 connector is the closest to the back
panel.

Figure 2. Stator Winding Leads

4. Connect the terminal ends of Wires 11, 22, 33 and 44
together. Make sure the wire ends are not touching any
part of the generator frame or any terminal.

5. Connect the red test probe of the Hi-Pot tester to the
joined terminal ends of stator leads 11, 22, 33 and 44.
Connect the black tester lead to a clean frame ground
on the stator can. With tester leads connected in this
manner, proceed as follows:

a.Turn the Hi-Pot tester switch OFF.
b.Plug the tester cord into a 120 volt AC wall

socket and set its voltage selector switch to
"1500 volts".

c.Turn the tester switch "On" and observe the

breakdown lamp on tester. DO NOT APPLY
VOLTAGE LONGER THAN 1 SECOND. After
one (1) second, turn the tester switch OFF.

If the breakdown lamp comes on during the one­second test, the stator should be cleaned and dried.
After cleaning and drying, repeat the insulation test. If,
after cleaning and drying, the stator fails the second
test, the stator assembly should be replaced.

6. Now proceed to the C2 connector. Each winding will be
individually tested for a short to ground. Insert a large
paper clip (or similar item) into the C2 connector at the
following pin locations:

Pin Wire Winding

Location Number

1 77 Battery Charge
2 66 Battery Charge
3 66A Engine Run
4 55 Engine Run
5 22 Sense Lead Power
6 11 Sense Lead Power
7 6 Excitation
8 2 Excitation

Next refer to Steps 5a through 5c of the Hi-Pot procedure.

Example: Insert paper clip into Pin 1, Hi-PPot from Pin
1 (Wire 77) to ground. Proceed to Pin 2, Pin 3, etc.
through Pin 8.

Figure 3. C2 Connector Pin Location Numbers

(Female Side)

TEST BETWEEN WINDINGS:

1. Insert a large paper clip into Pin Location 1 (Wire 77).
Connect the red tester probe to the paper clip. Connect
the black tester probe to Stator Lead 11. Refer to Steps
5a through 5c of “TESTING ALL STATOR WINDINGS
TO GROUND” on the previous page.

2. Repeat Step 1 at Pin Location 3 (Wire 66A) and Stator
Lead 11.

3. Repeat Step 1 at Pin Location 7 (Wire 6). and Stator
Lead 11.

4. Connect the red test probe to Stator Lead 33. Connect
the black test probe to Stator Lead 11. Refer to Steps
5a through 5c of “TESTING ALL STATOR WINDINGS
TO GROUND” on the previous page.

Page 1.4-5

SECTION 1.4

TESTING, CLEANING AND DRYING

PART 1

GENERAL INFORMATION

5. Insert a large paper clip into Pin Location No. 1 (Wire

77). Connect the red tester probe to the paper clip.
Connect the black tester probe to Stator Lead 33. Refer
to Steps 5a through 5c of “TESTING ALL STATOR
WINDINGS TO GROUND” on the previous page.

6. Repeat Step 5 at Pin Location 3 (Wire 66A) and Stator
Lead 33.

7. Repeat Step 5 at Pin Location 7 (Wire 6) and Stator
Lead 33.

For the following steps (8 through 10) an additional
large paper clip (or similar item) will be needed:

8. Insert a large paper clip into Pin Location 1 (Wire 77).
Connect the red tester probe to the paper clip. Insert the
additional large paper clip into Pin Location 3 (Wire
66A). Connect the black tester probe to this paper clip.
Refer to Steps 5a through 5c of “TESTING ALL
STATOR WINDINGS TO GROUND” on the previous
page.

9. Insert a large paper clip into Pin Location 1 (Wire 77).
Connect the red tester probe to the paper clip. Insert the
additional large paper clip into Pin Location 7 (Wire 6).
Connect the black tester probe to this paper clip. Refer
to Steps 5a through 5c of “TESTING ALL STATOR
WINDINGS TO GROUND” on the previous page.

10.Insert a large paper clip into Pin Location 3 (Wire 66A).
Connect the red tester probe to the paper clip. Insert the
additional large paper clip into Pin Location 7 (Wire 6).
Connect the black tester probe to this paper clip. Refer
to Steps 5a through 5c of “TESTING ALL STATOR
WINDINGS TO GROUND” on the previous page.

ROTOR INSULATION RESISTANCE TEST

Before attempting to test rotor insulation, the brush
holder must be completely removed. The rotor must
be completely isolated from other components before
starting the test. Attach all leads of all stator windings
to ground.

1. Connect the red tester lead to the positive (+) slip ring
(nearest the rotor bearing).

2. Connect the black tester probe to a clean frame ground,
such as a clean metal part of the rotor shaft.

3. Turn the tester switch OFF.

4. Plug the tester into a 120 volts AC wall socket and set
the voltage switch to "1500 volts".

5. Turn the tester switch "On" and make sure the pilot light
has turned on.

6. Observe the breakdown lamp, then turn the tester
switch OFF. DO NOT APPLY VOLTAGE LONGER
THAN ONE (1) SECOND.

If the breakdown lamp came on during the one (1)
second test, cleaning and drying of the rotor may be
necessary. After cleaning and drying, repeat the
insulation breakdown test. If breakdown lamp comes
on during the second test, replace the rotor assembly.

Figure 4. Testing Rotor Insulation

CLEANING THE GENERATOR

Caked or greasy dirt may be loosened with a soft
brush or a damp cloth. A vacuum system may be
used to clean up loosened dirt. Dust and dirt may also
be removed using dry, low-pressure air (25 psi
maximum).

CAUTION: Do not use sprayed water to clean
the generator. Some of the water will be
retained on generator windings and terminals,
and may cause very serious problems.

DRYING THE GENERATOR

To dry a generator, proceed as follows:

1. Open the generator main circuit breaker. NO
ELECTRICAL LOADS MUST BE APPLIED TO THE
GENERATOR WHILE DRYING.

2. Disconnect all Wires 4 from the voltage regulator.

3. Provide an external source to blow warm, dry air
through the generator interior (around the rotor and
stator windings. DO NOT EXCEED 185° F. (85° C.).

4. Start the generator and let it run for 2 or 3 hours.

5. Shut the generator down and repeat the stator and rotor
insulation resistance tests.

Page 1.4-6

SECTION 1.5

ENGINE-GENERATOR PROTECTIVE DEVICES

GENERAL INFORMATION

GENERAL

Standby electric power generators will often run
unattended for long periods of time. Such operating
parameters as (a) engine oil pressure, (b) engine
temperature, (c) engine operating speed, and (d)
engine cranking and startup are not monitored by an
operator during automatic operation. Because engine
operation will not be monitored, the use of engine
protective safety devices is required to prevent engine
damage in the event of a problem.

Prepackaged generator engines mount several engine
protective devices. These devices work in conjunction
with a circuit board, to protect the engine against such
operating faults as (a) low engine oil pressure, (b) high
temperature, (c) overspeed, and (d) overcrank. On
occurrence of any one or more of those operating faults,
circuit board action will effect an engine shutdown.

LOW OIL PRESSURE SHUTDOWN:

See Figure 1. An oil pressure switch is mounted on
the engine oil filter adapter. This switch has normally
closed contacts that are held open by engine oil
pressure during cranking and startup. Should oil
pressure drop below approximately 10 psi, the switch
contacts will close. On closure of the switch contacts,
a Wire 86 circuit from the circuit board will be
connected to ground. Circuit board action will then de­energize a "run relay" (on the circuit board). The run
relay’s normally open contacts will then open and a
12 volts DC power supply to a Wire 14 circuit will then
be terminated. This will result in closure of a fuel
shutoff solenoid and loss of engine ignition.

HIGH OIL TEMPERATURE SHUTDOWN:

An oil temperature switch (Figure 1) is mounted on
the engine block. The thermal switch has normally
open contacts that will close if oil temperature should
exceed approximately 284 F (140 C). This will result
in the same action as a low oil pressure shutdown.

OVERSPEED SHUTDOWN:

During engine cranking and operation, the circuit board
receives AC voltage and frequency signals from the
generator engine run windings, via Wire 66A. Should the
AC frequency exceed approximately 72Hz (4320 rpm),
circuit board action will de-energize a "run relay"
(mounted on the circuit board). The relay’s contacts will
open, to terminate engine ignition and close a fuel shutoff
solenoid. The engine will then shut down. This feature
protects the engine-generator against damaging
overspeeds.

NOTE: The circuit board also uses engine run
winding output to terminate engine cranking at
approximately 30 Hz (1800 rpm). In addition, the
engine run winding output is used by the circuit board
as an "engine running" signal The circuit board will
not initiate transfer of electrical loads to the "Standby"
source unless the engine is running at 30 Hz or

above.

Figure 1. Engine Protective Switches on an

Air-Cooled Engine

OVERCRANK SHUTDOWN:

Automatic engine cranking and startup normally
occurs when the circuit board senses that utility
source voltage has dropped below approximately 60
percent of its nominal rated voltage and remains at
that low level longer than fifteen (15) seconds. At the
end of fifteen (15) seconds, circuit board action will
energize a crank relay and a run relay (both relays
are on the circuit board). On closure of the crank relay
contacts, circuit board action will deliver 12 volts DC
to a starter contactor relay (SCR, for v-twin models)
or a starter contactor (SC, for single cylinder models).
The control contactor will energize and battery power
will be delivered to the starter motor (SM). The engine
will then crank.

During a manual startup (AUTO-OFF-MANUAL
switch at MANUAL), action is the same as during an
automatic start, except that cranking will begin
immediately when the switch is set to MANUAL.

Circuit board action (during both a manual and an
automatic start) will hold the crank relay energized for
15 seconds on. The relay will then de-energize for 15
seconds off. It will then energize for seven (7)
seconds on and de-energize for seven (7) seconds
off. It will repeat this same cycle for another 45
seconds.

If the engine has not started after approximately 90
seconds of these crank-rest cycles, cranking will
automatically terminate and shutdown will occur. The
circuit board uses AC signals from the stator engine
run winding as an indication that the engine has
started.

PART 1

Page 1.5-1

CONTROL PANEL

GENERAL:
See Figure 1. The front face of this panel mounts (a)

an hourmeter, (b) an AUTO-OFF-MANUAL switch ,(c)
a 15 amp fuse, (d) a 5 amp fuse, (e) a set exercise
switch and (f) the protection systems.

HOURMETER:

Equipped on some models only. The hourmeter
indicates engine-generator operating-time, in hours
and tenths of hours. Use the meter in conjunction with
the periodic maintenance schedule for the applicable
generator set. circuit board action turns the hourmeter
on at startup, via the same (Wire 14) circuit that
powers the engine ignition system and the fuel shutoff
solenoid.

Figure 1. Control Panel

AUTO-OFF-MANUAL SWITCH:

Use this switch to (a) select fully automatic operation,
(b) to crank and start the engine manually, and (c) to
shut the unit down or to prevent automatic startup.

1. AUTO position:

a.Select AUTO for fully automatic operation.

b.When AUTO is selected, circuit board will

monitor utility power source voltage.

c. Should utility voltage drop below a preset level

and remain at such a low level for a preset time,

circuit board action will initiate engine cranking
and startup.

d.Following engine startup, circuit board action

will initiate transfer of electrical loads to the
"Standby" source side.

e.On restoration of utility source voltage above a

preset level, circuit board action will initiate
retransfer back to the "Utility Source" side.

f. Following retransfer, circuit board will shut the

engine down and will then continue to monitor
utility source voltage.

2. OFF Position:

a.Set the switch to OFF to stop an operating

engine.

b.To prevent an automatic startup from occurring,

set the switch to OFF.

3. MANUAL Position:

a.Set switch to MANUAL to crank and start unit

manually.

b.Engine will crank cyclically and start (same as

automatic startup, but without transfer). The unit
WILL transfer if utility voltage is not available.

DANGER: WHEN THE GENERATOR IS
INSTALLED IN CONJUNCTION WITH AN
AUTOMATIC TRANSFER SWITCH, ENGINE
CRANKING AND STARTUP CAN OCCUR AT
ANY TIME WITHOUT WARNING (PROVIDING
THE AUTO-OFF-MANUAL SWITCH IS SET TO
AUTO). TO PREVENT AUTOMATIC STARTUP
AND POSSIBLE INJURY THAT MIGHT BE
CAUSED BY SUCH STARTUP, ALWAYS SET
THE AUTO-OFF-MANUAL SWITCH TO ITS
OFF POSITION BEFORE WORKING ON OR
AROUND THIS EQUIPMENT.

15 AMP FUSE:

This fuse protects the DC control circuit (including the
circuit board) against overload. If the fuse element
has melted open due to an overload, engine cranking
or running will not be possible. Should fuse
replacement become necessary, use only an identical
15 amp replacement fuse.

5 AMP FUSE:

This fuse protects the battery charge circuit against
overload. If the fuse element has melted open due to
an overload, battery charge will not occur. Should
fuse replacement become necessary, use only an
identical 5 amp replacement fuse.

PART 1

GENERAL INFORMATION

SECTION 1.6

OPERATING INSTRUCTIONS

Page 1.6-1

SECTION 1.6

OPERATING INSTRUCTIONS

THE SET EXERCISE SWITCH:

The air-cooled, prepackaged automatic standby
generator will start and exercise once every seven (7)
days, on a day and at a time of day selected by the
owner or operator. The set exercise time switch is
provided to select the day and time of day for system
exercise.

See Page 5.1-3 ("The 7-Day Exercise Cycle") for
instructions on how to set exercise time.

DANGER: THE GENERATOR WILL CRANK
AND START WHEN THE SET EXERCISE TIME
SWITCH IS SET TO "ON". DO NOT ACTUATE
THE SWITCH TO "ON" UNTIL AFTER YOU
HAVE READ THE INSTRUCTIONS IN PART 5.

PROTECTION SYSTEMS:

Unlike an automobile engine, the generator may have
to run for long periods of time with no operator
present to monitor engine conditions. For that reason,
the engine is equipped with the following systems that
protect it against potentially damaging conditions:

❏ Low Oil Pressure Sensor
❏ High Temperature Sensor
❏ Overcrank
❏ Overspeed

There are LED readouts on the control panel to notify
you that one of these faults has occurred. There is
also a System Set LED that is lit when all of the
following conditions are true:

1. The AUTO-OFF-MANUAL switch is set to the AUTO
position.

2. The NOT IN AUTO dip switch is set to the OFF position
on the control board.

3. No alarms are present.

TO SELECT AUTOMATIC OPERATION

The following procedure applies only to those
installations in which the air-cooled, prepackaged
automatic standby generator is installed in
conjunction with a prepackaged transfer switch.
Prepackaged transfer switches do not have an
intelligence circuit of their own, as do Generac "GTS"
type transfer switches. Instead, automatic operation
on prepackaged transfer switch and generator
combinations is controlled by circuit board action.

To select automatic operation when a prepackaged
transfer switch is installed along with a prepackaged
home standby generator, proceed as follows:

1. Check that the prepackaged transfer switch main
contacts are at their UTILITY position, i.e., the load is
connected to the utility power supply. If necessary,
manually actuate the switch main contacts to their
UTILITY source side. See Part 5 of this manual, as
appropriate, for instructions.

2. Check that utility source voltage is available to transfer
switch terminal lugs N1 and N2 (2-pole, 1-phase
transfer switches).

3. Set the generator AUTO-OFF-MANUAL switch to its
AUTO position.

4. Actuate the generator main line circuit breaker to its "On"
or "Closed" position. With the preceding Steps 1 through
4 completed, a dropout in utility supply voltage below a
preset level will result in automatic generator cranking
and start-up. Following startup, the prepackaged transfer
switch will be actuated to its "Standby" source side, i.e.,
loads powered by the standby generator.

MANUAL TRANSFER TO "STANDBY" AND

MANUAL STARTUP

To transfer electrical loads to the "Standby"
(generator) source and start the generator manually,
proceed as follows:

1. On the generator panel, set the AUTO-OFF-MANUAL
switch to OFF.

2. On the generator, set the main line circuit breaker to it's
OFF or "Open" position.

3. Turn OFF the utility power supply to the transfer switch,
using whatever means provided (such as a utility source
line circuit breaker).

4. Manually actuate the transfer switch main contacts to
their “Standby” position, i.e., loads connected to the
“Standby” power source side.

NOTE: For instructions on manual operation of
prepackaged transfer switches, see Part 5.

5. On the generator panel, set the AUTO-OFF-MANUAL
switch to MANUAL. The engine should crank and start.

6. Let the engine warm up and stabilize for a minute or two
at no-load.

GENERAL INFORMATION

PART 1

Page 1.6-2

SECTION 1.6

OPERATING INSTRUCTIONS

7. Set the generator main line circuit breaker to its "On" or
"Closed" position. The generator now powers the
electrical loads.

MANUAL SHUTDOWN AND RETRANSFER

BACK TO "UTILITY"

To shut the generator down and retransfer electrical
loads back to the UTILITY position, proceed as
follows:

1. Set the generator main line circuit breaker to its OFF or
"Open" position.

2. Let the generator run at no-load for a few minutes, to cool.

3. Set the generator AUTO-OFF-MANUAL switch to OFF.
Wait for the engine to come to a complete stop.

4. Turn off the utility power supply to the transfer switch
using whatever means provided (such as a utility source
main line circuit breaker)

5. Manually actuate the prepackaged transfer switch to its
UTILITY source side, i.e., load connected to the utility
source.

6. Turn on the utility power supply to the transfer switch,
using whatever means provided.

7. Set the generator AUTO-OFF-MANUAL switch to
AUTO.

PART 1

GENERAL INFORMATION

Page 1.6-3

GENERAL INFORMATION

SECTION 1.7

AUTOMATIC OPERATING PARAMETERS

INTRODUCTION

When the prepackaged generator is installed in
conjunction with a prepackaged transfer switch, either
manual or automatic operation is possible. Manual
transfer and engine startup, as well as manual
shutdown and retransfer are covered in Section 1.6.
Selection of fully automatic operation is also
discussed in that section. This section will provide a
step-by-step description of the sequence of events
that will occur during automatic operation of the
system.

AUTOMATIC OPERATING SEQUENCES

PHASE 1 - UTILITY VOLTAGE AVAILABLE:

With utility source voltage available to the transfer
switch, that source voltage is sensed by a circuit
board in the generator panel and the circuit board
takes no action.

Electrical loads are powered by the

utility source and

the AUTO-OFF-MANUAL switch is set to AUTO.

PHASE 2- UTILITY VOLTAGE DROPOUT:

If a dropout in utility source voltage should occur
below about 60 percent of the nominal utility source
voltage, a 15 second timer on the circuit board will
start timing. This timer is required to prevent false
generator starts that might be caused by transient
utility voltage dips.

PHASE 3- ENGINE CRANKING:

When the circuit board’s 15 second timer has finished
timing and if utility source voltage is still below 60
percent of the nominal source voltage, circuit board
action will energize a crank relay and a run relay.
Both of these relays are mounted on the circuit board.

If the engine starts, cranking will terminate when
generator AC output frequency reaches
approximately 30 Hz.

PHASE 4-ENGINE STARTUP AND RUNNING:

The circuit board senses that the engine is running by
receiving a voltage/frequency signal from the engine
run windings.

When generator AC frequency reaches approximately
30 Hz, an engine warm-up timer on the circuit board
turns on. That timer will run for about ten (10)
seconds.

The engine warm-up timer lets the engine warm-up
and stabilize before transfer to the "Standby" source
can occur.

NOTE: The engine can be shut down manually at any
time, by setting the AUTO-OOFF-MMANUAL switch to
OFF.

PHASE 5- TRANSFER TO "STANDBY":

When the circuit board’s engine warm-up timer has
timed out and AC voltage has reached 50 percent of
the nominal rated voltage, circuit board action
completes a transfer relay circuit to ground. The
transfer relay is housed in the prepackaged transfer
switch enclosure.

The transfer relay energizes and transfer of loads to
the "Standby" power source occurs. Loads are now
powered by standby generator AC output.

PHASE 6- "UTILITY" POWER RESTORED:

When utility source voltage is restored above about
80 percent of the nominal supply voltage, a 15
second timer on the circuit board starts timing. If utility
voltage remains sufficiently high at the end of 15
seconds, retransfer can occur.

PHASE 7- RETRANSFER BACK TO "UTILITY":

At the end of the 15 second delay, circuit board action
will open a circuit to a transfer relay (housed in the
transfer switch). The transfer relay will then de­energize and retransfer back to the utility source will
occur. Loads are now powered by utility source
power. On retransfer, an engine cool-down timer
starts timing and will run for about one (1) minute.

PHASE 8- GENERATOR SHUTDOWN:

When the engine cool-down timer has finished timing,
and if the minimum run timer has timed out, engine
shutdown will occur.

PART 1

Page 1.7-1

SECTION 1.7

AUTOMATIC OPERATING PARAMETERS

PART 1

GENERAL INFORMATION

Page 1.7-2

AUTOMATIC OPERATING SEQUENCES CHART

SEQ. CONDITION ACTION SENSOR, TIMER OR OTHER

1 Utility source voltage is No action Voltage Dropout Sensor on circuit

available. circuit board.

2 Utility voltage dropout below A 15-second timer on circuit Voltage Dropout Sensor and 15

60% of rated voltage occurs. board turns on. second timer on circuit board.

3 Utility voltage is still below 15-second timer runs for 15 Voltage Dropout Sensor and 15

60% of rated voltage. seconds, then stops. second timer.

4 Utility voltage is still low after Circuit board action energizes a Circuit board crank and run

15 seconds. crank relay and a run relay. relays.

See NOTE 1.

5 Utility voltage still low and Circuit board s engine warmup Engine Warmup Timer (10 seconds)

the engine has started. timer runs for 10 seconds.

6 Engine running and engine Circuit board action energizes a Circuit board transfer relay circuit

warmup timer times out. transfer relay in transfer switch Transfer switch transfer relay.
AC output voltage above and transfer to Standby occurs.
50% nominal voltage.

7 Engine running and load is No further action Circuit board voltage pickup

powered by Standby power. sensor continues to seek an

acceptable Utility voltage.

8 Utility source voltage is Circuit board voltage pickup Voltage Pickup Sensor (80%)

restored above 80% of rated sensor reacts and a re-transfer Return to Utility Timer (15 seconds)

time delay turns on.

9 Utility voltage still high after 15 Return to Utility Timer times out Return to Utility Timer

seconds.

10 Utility voltage still high. Circuit board action opens the Circuit board transfer relay circuit

transfer relay circuit to ground. Transfer switch transfer relay.
Transfer relay de-energizes and
retransfer to Utility occurs.

11 Engine still running, loads are Circuit board engine cool down Circuit board Engine Cool down

powered by Utility source. timer starts running. Timer (1 minute)

12 After 1 minute, engine cool down Engine Cool down Timer

timer stops and circuit board s Circuit board Run Relay.
run relay de-energizes. Engine
shuts down.

13 Engine is shut down, loads are No action. Voltage Dropout Sensor on circuit

powered by Utility source. circuit board.
Return to Sequence 1.

PART 2

AC GENERATORS

TABLE OF CONTENTS

PART TITLE

2.1 Description and Components

2.2 Operational Analysis

2.3 Troubleshooting Flow Charts

2.4 Diagnostic Tests

Air-cooled, Prepackaged

Automatic Standby Generators

Models:

04389, 04758 (6 kW NG, 7 kW LP)
04456, 04759 (12 kW NG, 12 kW LP)
04390, 04760 (13 kW NG, 15 kW LP)

SECTION 2.1

DESCRIPTION & COMPONENTS

PART 2

Page 2.1-1

AC GENERATORS

INTRODUCTION

The air-cooled, pre-packaged automatic standby
system is an easy to install, fully enclosed and self­sufficient electric power system. It is designed
especially for homeowners, but may be used in other
applications as well. On occurrence of a utility power
failure, this high performance system will (a) crank
and start automatically, and (b) automatically transfer
electrical loads to generator AC output.

The generator revolving field (rotor) is driven by an
air-cooled engine at about 3600 rpm.

The generator may be used to supply electrical power
for the operation of 120 and/or 240 volts, 1phase, 60
Hz, AC loads.

A 2-pole, "V-Type", prepackaged transfer switch is
shipped with the unit (see Part 3). Prepackaged
transfer switches do not include an "intelligence
circuit" of their own. Instead, automatic startup,
transfer, running, retransfer and shutdown operations
are controlled by a solid state circuit board in the
generator control panel.

ENGINE-GGENERATOR DRIVE SYSTEM

The generator revolving field is driven by an air­cooled, horizontal crankshaft engine. The generator is

directly coupled to the engine crankshaft (see Figure

1), and mounted in an enclosure. Both the engine and
generator rotor are driven at approximately 3600 rpm,
to provide a 60 Hz AC output.

THE AC GENERATOR

Figure 1 shows the major components of the AC
generator.

ROTOR ASSEMBLY

The 2-pole rotor must be operated at 3600 rpm to
supply a 60 Hertz AC frequency. The term "2-pole"
means the rotor has a single north magnetic pole and
a single south magnetic pole. As the rotor rotates, its
lines of magnetic flux cut across the stator assembly
windings and a voltage is induced into the stator
windings. The rotor shaft mounts a positive (+) and a
negative (-) slip ring, with the positive (+) slip ring
nearest the rear bearing carrier. The rotor bearing is
pressed onto the end of the rotor shaft. The tapered
rotor shaft is mounted to a tapered crankshaft and is
held in place with a single through bolt.

Figure 1. AC Generator Exploded View

SECTION 2.1

DESCRIPTION & COMPONENTS

AC GENERATORS

PART 2

Page 2.1-2

Figure 2. The 2-Pole Rotor Assembly

STATOR ASSEMBLY

The stator can houses and retains (a) dual AC power
windings, (b) excitation winding, (c) battery charge
winding and (d) engine run winding. A total of twelve
(12) stator leads are brought out of the stator can as
shown in Figure 3.

The stator can is sandwiched between an engine
adapter and a rear bearing carrier. It is retained in
that position by four stator studs.

Figure 3 Stator Assembly Leads

BRUSH HOLDER AND BRUSHES

The brush holder is retained to the rear bearing carrier
by means of two #10-32 x 9/16 Taptite screws. A
positive (+) and a negative (-) brush are retained in the
brush holder, with the positive (+) brush riding on the
slip ring nearest the rotor bearing.

Wire 4 connects to the positive (+) brush and Wire 0 to
the negative (-) brush. Wire 0 connects to frame
ground. Rectified and regulated excitation current, as
well as current from a field boost circuit, are delivered
to the rotor windings via Wire 4, and the positive (+)
brush and slip ring. The excitation and field boost
current passes through the windings and to frame
ground via the negative (-) slip ring and brush, and
Wire 0. This current flow creates a magnetic field
around the rotor having a flux concentration that is
proportional to the amount of current flow.

Figure 4. Brush Holder and Brushes

OTHER AC GENERATOR COMPONENTS

Some AC generator components are housed in the
generator control panel enclosure, and are not shown
in Figure 1. These are (a) an excitation circuit breaker,
(b) a voltage regulator, and (c) a main line circuit
breaker.

EXCITATION CIRCUIT BREAKER:

The excitation circuit breaker (CB2) is housed in the
generator panel enclosure and electrically connected
in series with the excitation (DPE) winding output to
the voltage regulator. The breaker is self-resetting, i.e.;
its contacts will close again when excitation current
drops to a safe value.

If the circuit breaker has failed open, excitation current
flow to the voltage regulator and, subsequently, to the
rotor windings will be lost. Without excitation current
flow, AC voltage induced into the stator AC power
windings will drop to a value that is commensurate with
the rotor residual magnetism (see Figure 5).

SECTION 2.1

DESCRIPTION & COMPONENTS

PART 2

AC GENERATORS

Figure 5. Excitation Circuit Breaker

VOLTAGE REGULATOR:

A typical voltage regulator is shown in Figure 6.
Unregulated AC output from the stator excitation
winding is delivered to the regulator’s DPE terminals,
via Wire 2, the excitation circuit breaker, Wire 162,
and Wire 6. The voltage regulator rectifies that
current and, based on stator AC power winding
sensing, regulates it. The rectified and regulated
excitation current is then delivered to the rotor
windings from the positive (+) and negative (-)
regulator terminals, via Wire 4 and Wire 1. Stator AC
power winding sensing is delivered to the regulator
"SEN" terminals via Wires 11 and 22.

The regulator provides "over-voltage" protection, but
does not protect against "under-voltage". On
occurrence of an "over-voltage’ condition, the
regulator will "shut down" and complete loss Of
excitation current to the rotor will occur. Without
excitation current, the generator AC output voltage
will drop to approximately one-half (or lower) of the
unit’s rated voltage.

Figure 6. Typical Voltage Regulator

A single red lamp (LED) glows during normal
operation. The lamp will become dim if excitation
winding AC output diminishes. It will go out on
occurrence of an open condition in the sensing AC
output circuit.

An adjustment potentiometer permits the stator AC
power winding voltage to be adjusted. Perform this
adjustment with the generator running at no-load, and
with a 62 Hz AC frequency (62 Hz equals 3720 rpm).
At the stated no-load frequency, adjust to obtain a
line-to-line AC voltage of about 252 volts.

MAIN LINE CIRCUIT BREAKER:

The main line circuit breaker protects the generator
against electrical overload. See Specifications on
Page 1 for amp ratings.

Page 2.1-3

SECTION 2.2

OPERATIONAL ANALYSIS

AC GENERATORS

ROTOR RESIDUAL MAGNETISM

The generator revolving field (rotor) may be
considered to be a permanent magnet. Some
’residual" magnetism is always present in the rotor.
This residual magnetism is sufficient to induce a
voltage into the stator AC power windings that is
approximately 2-12 volts AC.

FIELD BOOST

FIELD BOOST CIRCUIT:
When the engine is cranking, direct current flow is

delivered from a circuit board to the generator rotor
windings, via Wire 4.

The field boost system is shown schematically in
Figure 2. Manual and automatic engine cranking is
initiated by circuit board action, when that circuit
board energizes a crank relay (K1). Battery voltage is
then delivered to field boost Wire 4 (and to the rotor),
via a field boost resistor and diode. The crank relay,
field boost resistor and diode are all located on the
circuit board.

Notice that field boost current is available only while
the crank relay (K1) is energized, i.e., while the
engine is cranking.

Field boost voltage is reduced from that of battery
voltage by the resistor action and, when read with a
DC voltmeter, will be approximately 9 or 10 volts DC.

Figure 2. Field Boost Circuit Schematic

PART 2

Page 2.2-1

Figure 1. Operating Diagram of AC Generator