Guardian 4721 Operating instructions

PO BOX 297
WHITEWATER, WI 53190
www.guardiangenerators.com
P/N 0F7698 Rev. 0 / Printed in the USA / 8.05
Models: 4721, 4722, 4723, 4724, 4725, 4726
1.5L HOME STANDBY GENERATORS www.guardiangenerators.com
LIQUID-COOLED
DIAGNOSTIC
REPAIR MANUAL

Page ii
Study these SAFETY RULES carefully before installing, operating or servicing this equipment. Become famil-
iar with the Owner’s Manual and with the unit. The generator can operate safely, efficiently and reliably only
if it is properly installed, operated and maintained. Many accidents are caused by failing to follow simple and
fundamental rules or precautions.
Generac cannot anticipate every possible circumstance that might involve a hazard. The warnings in this
manual, and on tags and decals affixed to the unit are, therefore, not all-inclusive. If using a procedure,
work method or operating technique that Generac does not specifically recommend, ensure that it is safe
for others. Also make sure the procedure, work method or operating technique utilized does not render
the generator unsafe.
Despite the safe design of this generator, operating this equipment imprudently, neglecting its main-
tenance or being careless can cause possible injury or death. Permit only responsible and capable
persons to install, operate or maintain this equipment.
Potentially lethal voltages are generated by these machines. Ensure all steps are taken to render the
machine safe before attempting to work on the generator.
Parts of the generator are rotating and/or hot during operation. Exercise care near running genera-
tors.
!
!
DANGER
SAVE THESE INSTRUCTIONS – The manufacturer suggests that these rules for safe opera-
tion be copied and posted in potential hazard areas. Safety should be stressed to all opera-
tors and potential operators of this equipment.
!
Important Safety Notice
Proper service and repair is important to the safe, economical and reliable operation of all
standby electric power systems. The troubleshooting, testing and servicing procedures recom-
mended by Generac and described in this manual are effective methods of performing such
operations. Some of these operations or procedures may require the use of specialized equip-
ment. Such equipment should be used when and as recommended.
It is important to note that this manual contains various DANGER, CAUTION, and NOTE blocks.
These should be read carefully in order to minimize the risk of personal injury or to prevent
improper methods or practices from being used. Use of improper or unauthorized practices
may damage equipment or render it unsafe. The DANGER, CAUTION and NOTE blocks are not
exhaustive. Generac could not possibly know, evaluate and advise the service trade of all con-
ceivable ways in which operations described in this manual might be accomplished or of the
possible hazardous consequences of each way. Consequently, Generac has not taken any such
broad evaluation. Accordingly, anyone who uses any troubleshooting, testing or service proce-
dure that is not recommended by Generac must first satisfy himself that neither his safety nor
the equipment's safety will be jeopardized by the procedure or the method he selects.

Page iii
GENERAL HAZARDS
• For safety reasons, Generac recommends that this equipment be installed, serviced and repaired by an
authorized service dealer or other competent, qualified electrician or installation technician who is
familiar with applicable codes, standards and regulations. The operator also must comply with all
such codes, standards and regulations.
• Installation, operation, servicing and repair of this (and related) equipment must always comply with
applicable codes, standards, laws and regulations. Adhere strictly to local, state and national electrical
and building codes. Comply with regulations the Occupational Safety and Health Administration
(OSHA) has established. Also, ensure that the generator is installed, operated and serviced in accor-
dance with the manufacturer’s instructions and recommendations. Following installation, do nothing
that might render the unit unsafe or in noncompliance with the aforementioned codes, standards, laws
and regulations.
• The engine exhaust fumes contain carbon monoxide gas, which can be DEADLY. This dangerous gas, if
breathed in sufficient concentrations, can cause unconsciousness or even death. For that reason, ade-
quate ventilation must be provided. Exhaust gases must be piped safely away from any building or
enclosure that houses the generator to an area where people, animals, etc., will not be harmed. This
exhaust system must be installed properly, in strict compliance with applicable codes and standards.
• Keep hands, feet, clothing, etc., away from drive belts, fans, and other moving or hot parts. Never
remove any drive belt or fan guard while the unit is operating.
• Adequate, unobstructed flow of cooling and ventilating air is critical to prevent buildup of explosive
gases and to ensure correct generator operation. Do not alter the installation or permit even partial
blockage of ventilation provisions, as this can seriously affect safe operation of the generator.
• Keep the area around the generator clean and uncluttered. Remove any materials that could become
hazardous.
• When working on this equipment, remain alert at all times. Never work on the equipment when physi-
cally or mentally fatigued.
• Inspect the generator regularly, and promptly repair or replace all worn, damaged or defective parts
using only factory-approved parts.
• Before performing any maintenance on the generator, disconnect its battery cables to prevent acciden-
tal start-up. Disconnect the cable from the battery post indicated by a NEGATIVE, NEG or (–) first.
Reconnect that cable last.
• Never use the generator or any of its parts as a step. Stepping on the unit can stress and break parts,
and may result in dangerous operating conditions from leaking exhaust gases, fuel leakage, oil leakage,
etc.
ELECTRICAL HAZARDS
• All generators covered by this manual produce dangerous electrical voltages and can cause fatal electri-
cal shock. Utility power delivers extremely high and dangerous voltages to the transfer switch as well as
the standby generator. Avoid contact with bare wires, terminals, connections, etc., on the generator as
well as the transfer switch, if applicable. Ensure all appropriate covers, guards and barriers are in place
before operating the generator. If work must be done around an operating unit, stand on an insulated,
dry surface to reduce shock hazard.
• Do not handle any kind of electrical device while standing in water, while barefoot, or while hands or
feet are wet. DANGEROUS ELECTRICAL SHOCK MAY RESULT.
• If people must stand on metal or concrete while installing, operating, servicing, adjusting or repairing
this equipment, place insulative mats over a dry wooden platform. Work on the equipment only while
standing on such insulative mats.
!!

Page iv
• The National Electrical Code (NEC), Article 250 requires the frame and external electrically conductive
parts of the generator to be connected to an approved earth ground and/or grounding rods. This
grounding will help prevent dangerous electrical shock that might be caused by a ground fault condi-
tion in the generator set or by static electricity. Never disconnect the ground wire.
• Wire gauge sizes of electrical wiring, cables and cord sets must be adequate to handle the maximum
electrical current (ampacity) to which they will be subjected.
• Before installing or servicing this (and related) equipment, make sure that all power voltage supplies
are positively turned off at their source. Failure to do so will result in hazardous and possibly fatal
electrical shock.
• Connecting this unit to an electrical system normally supplied by an electric utility shall be by means of
a transfer switch so as to isolate the generator electric system from the electric utility distribution sys-
tem when the generator is operating. Failure to isolate the two electric system power sources from each
other by such means will result in damage to the generator and may also result in injury or death to
utility power workers due to backfeed of electrical energy.
• Generators installed with an automatic transfer switch will crank and start automatically when NOR-
MAL (UTILITY) source voltage is removed or is below an acceptable preset level. To prevent such auto-
matic start-up and possible injury to personnel, disable the generator’s automatic start circuit (battery
cables, etc.) before working on or around the unit. Then, place a “Do Not Operate” tag on the generator
control panel and on the transfer switch.
• In case of accident caused by electric shock, immediately shut down the source of electrical power. If
this is not possible, attempt to free the victim from the live conductor. AVOID DIRECT CONTACT
WITH THE VICTIM. Use a nonconducting implement, such as a dry rope or board, to free the victim
from the live conductor. If the victim is unconscious, apply first aid and get immediate medical help.
• Never wear jewelry when working on this equipment. Jewelry can conduct electricity resulting in elec-
tric shock, or may get caught in moving components causing injury.
FIRE HAZARDS
• Keep a fire extinguisher near the generator at all times. Do NOT use any carbon tetra-chloride type
extinguisher. Its fumes are toxic, and the liquid can deteriorate wiring insulation. Keep the extinguisher
properly charged and be familiar with its use. If there are any questions pertaining to fire extinguish-
ers, consult the local fire department.
EXPLOSION HAZARDS
• Properly ventilate any room or building housing the generator to prevent build-up of explosive gas.
• Do not smoke around the generator. Wipe up any fuel or oil spills immediately. Ensure that no com-
bustible materials are left in the generator compartment, or on or near the generator, as FIRE or
EXPLOSION may result. Keep the area surrounding the generator clean and free from debris.
• Generac generator sets may operate using one of several types of fuels. All fuel types are potentially
FLAMMABLE and/or EXPLOSIVE and should be handled with care. Comply with all laws regulating
the storage and handling of fuels. Inspect the unit’s fuel system frequently and correct any leaks imme-
diately. Fuel supply lines must be properly installed, purged and leak tested according to applicable
fuel-gas codes before placing this equipment into service.
• Diesel fuels are highly FLAMMABLE. Gaseous fluids such as natural gas and liquid propane (LP) gas
are extremely EXPLOSIVE. Natural gas is lighter than air, and LP gas is heavier than air; install leak
detectors accordingly.

Page 1
PART TITLE PAGE
SPECIFICATIONS 2
1 General Information 3
2 Prepackaged Liquid Cooled AC Generators 19
3 V-Type Prepackaged Transfer Switches 39
4 DC Control- Units with Liquid-Cooled Engine 57
5 Operational Tests and Adjustments 95
6 Electrical Data 101
TABLE OF CONTENTS
1.5 LITER PREPACKAGED
HOME STANDBY
GENERATORS
DIAGNOSTIC
REPAIR MANUAL

Page 2
GENERATOR SPECIFICATIONS
Phase ............................................................ Single
Rated Max. Cont. AC Power Output (kW) ......... 15*
Rated Voltage (volts) ................................. 120/240
No. of Rotor Poles - 15 kW ................................... 2
No. of Rotor Poles - 20/25 kW .............................. 4
Driven Speed of Rotor - 15 kW ....................... 1800
Driven Speed of Rotor - 20/25 kW .................. 3600
Rotor Excitation System .. Direct excited brush type
Rotor/Stator Insulation ................................ Class F
* Rated power of generator is subject to and limited
by such factors as ambient temperature, altitude,
engine condition, and other factors. Engine power
will decrease about 3% for each 1000 feet above
600 feet and will decrease an additional 1.65% for
each 10°F above 77°F. Maximum output power of
the generator is limited by maximum engine power.
ENGINE SPECIFICATIONS
Make .........................................................Mitsubishi
Displacement.............................................92 inches
(1.5 liters)
Cylinder Arrangement .................................4, in-line
Valve Arrangement...........................Overhead Cam
Firing Order ...................................................1-3-4-2
Number of Main Bearings .......................................5
Compression Ratio ..........................................9 to 1
No. of Teeth on Flywheel....................................104
Ignition Timing
at 1800 rpm..................................35 degrees BTDC
Spark Plug Gap..............................0.020-0.025 inch
Recommended Spark Plugs
Champion .................................................RN11YC4
Oil Pressure ...............................................30-50 psi
Crankcase Oil Capacity ...3.0 U.S. quarts (2.8 liters)
Recommended Engine Oil ...................SAE 15W-40
Type of Cooling SystemPressurized, closed recovery
Cooling Fan ..........................................Pusher Type
Cooling System Capacity ..2 U.S. gallons (7.6 liters)
Recommended Coolant........Use a 50-50 mixture of
ethylene glycol base.
FUEL CONSUMPTION
25 kW Models
Using Natural Gas .................... 441 cu. ft. per hour
Using LP Gas.......... 175 cubic ft. (4.8 gal.) per hour
20 kW Models
Using Natural Gas .................... 359 cu. ft. per hour
Using LP Gas ......... 143 cubic ft. (4.0 gal.) per hour
15 kW Models
Using Natural Gas .................... 277 cu. ft. per hour
Using LP Gas .......... 110 cubic ft.(3.1 gal.) per hour
NOTE: Fuel consumption is given at rated maxi-
mum continuous power output when using natural
gas rated at 1000 Btu per cubic foot and LP gas
rated 2520 Btu per cubic foot. Actual fuel con-
sumption obtained may vary depending on such
variables as applied load, ambient temperature,
engine conditions and other environmental factors.
Fuel pressure for a natural gas set up should be five
inches to 14 inches of water column (0.18 to 0.5 psi)
at all load ranges.
Fuel pressure for an LP vapor set up should be 11
inches to 14 inches of water column (0.4 to 0.5 psi) at
all load ranges.
ENGINE OIL RECOMMENDATIONS
The unit has been filled with 15W-40 engine oil at the
factory. Use a high-quality detergent oil classified “For
Service SJ or latest available.” Detergent oils keep
the engine cleaner and reduce carbon deposits. Use
oil having the following SAE viscosity rating, based on
the ambient temperature range anticipated before the
next oil change:
NOTE: Synthetic oil is highly recommended when
the generator will be operating in ambient temper-
atures which regularly exceed 90° F and/or fall
below 30° F.
ANY ATTEMPT TO CRANK OR START THE
ENGINE BEFORE IT HAS BEEN PROPERLY
SERVICED WITH THE RECOMMENDED OIL
MAY RESULT IN AN ENGINE FAILURE.
COOLANT RECOMMENDATIONS
Use a mixture of half low silicate ethylene glycol base
anti-freeze and deionized water. Cooling system
capacity is about 8 U.S. quarts (7.6 liters). Use only
deionized water and only low silicate anti-freeze. If
desired, add a high quality rust inhibitor to the recom-
mended coolant mixture. When adding coolant,
always add the recommended 50-50 mixture.
DO NOT USE ANY CHROMATE BASE RUST
INHIBITOR WITH ETHYLENE GLYCOL BASE
ANTI-FREEZE OR CHROMIUMHYDROXIDE
(“GREEN SLIME”) FORMS AND WILL CAUSE
OVERHEATING. ENGINES THAT HAVE BEEN
OPERATED WITH A CHROMATE BASE RUST
INHIBITOR MUST BE CHEMICALLY CLEANED
BEFORE ADDING ETHYLENE GLYCOL BASE
ANTI-FREEZE. USING ANY HIGH SILICATE
ANTI-FREEZE BOOSTERS OR ADDITIVES WILL
ALSO CAUSE OVERHEATING. IT IS ALSO REC-
OMMENDED THAT ANY SOLUBLE OIL
INHIBITOR IS NOT USED FOR THIS EQUIPMENT.
!
!
SPECIFICATIONS
Temperature Oil Grade (Recommended)
Above 80° F (27° C) SAE 30W or 15W-40
32° to 80° F (-1° to 27° C) SAE 20W-20 or 15W-40
Below 32° F (0° C) SAE 10W or 15W-40

Page 3
PART TITLE PAGE
1.1 Generator Identification 4
1.2 Prepackaged Installation Basics 6
1.3 Preparation Before Use 9
1.4 Testing, Cleaning and Drying 10
1.5 Engine-Generator Protective Devices 13
1.6 Operating Instructions 15
1.7 Automatic Operating Parameters 17
TABLE OF CONTENTS
1.5 LITER PREPACKAGED
HOME STANDBY
GENERATORS
PART 1
GENERAL
INFORMATION

FUSE
15-A
AGC
FAULT
INDICATOR
AUTO
OFF
ON
SET
EXERCISE
TIME
MANUAL
STARTER
DATA PLATE
HOURMETER
15 AMP FUSE
FAULT INDICATOR
CIRCUIT BREAKER
SET EXERCISE SWITCH
AUTO-OFF-MANUAL SWITCH
ALTERNATOR
CARBURETOR MUFFLER
RADIATOR
ENGINE
FUEL REGULATOR
BATTERY
DISTRIBUTOR
CONTROL PANEL
HOURMETER
PART 1 GENERAL INFORMATION
SECTION 1.1
GENERATOR IDENTIFICATION
Page 4

PART 1
GENERAL INFORMATION SECTION 1.1
GENERATOR IDENTIFICATION
INTRODUCTION
This Diagnostic Repair Manual has been prepared
especially for the purpose of familiarizing service per-
sonnel with the testing, troubleshooting and repair of
prepackaged home standby generator systems.
Every effort has been expended to ensure that infor-
mation and instructions in the manual are both accu-
rate and current. However, the manufacturer reserves
the right to change, after or otherwise improve the
product at any time without prior notification.
The manual has been divided into several PARTS.
Each PART has been divided into SECTIONS. Each
SECTION consists of two or more SUBSECTIONS.
It is not the manufacturers intent to provide detailed
disassembly and reassembly instructions in this man-
ual. It is the manufacturers 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.
UNITS WITH LIQUID COOLED ENGINE
A typical prepackaged generator with liquid cooled
engine is shown on Page 4 at front of this manual.
A DATA PLATE, affixed to the unit, contains impor-
tant information pertaining to the unit, including its
Model Number, Serial Number, kW rating, rated rpm,
rated voltage, etc. The information from this data
plate may be required when requesting information,
ordering parts, etc.
Figure 1. A Typical Data Plate
Page 5

INTRODUCTION
Information in this section is provided so that the ser-
vice technician will have a basic knowledge of instal-
lation 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, below. Installation of such a sys-
tem includes the following:
• Selecting a Location
• Mounting of the generator.
• Grounding the generator.
• Providing a fuel supply.
• Mounting the transfer switch.
• 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.
MOUNTING THE GENERATOR
Mount the generator set to a concrete slab. The slab
should extend past the generator and to a distance of at
least twelve (12) inches on all sides. The unit can be
retained to the concrete slab with masonry anchor bolts.
GROUNDING THE GENERATOR
The National Electric Code requires that the frame
and external electrically conductive parts of the gen-
erator be property connected to an approved earth
ground. Local electrical codes may also require prop-
er grounding of the unit. For that purpose, a ground-
ing lug is attached to the unit. Grounding may be
accomplished by attaching a stranded copper wire of
the proper size to the generator’s grounding lug and
to an earth-driven copper or brass grounding-rod
(electrode). Consult with a local electrician for ground-
ing requirements in your area.
THE FUEL SUPPLY
Units with liquid cooled engines are shipped from the
factory to run on natural gas (Figure 2). Units that will
use LP (propane) gas fuel (Figure 3) must be convert-
ed in the field per instructions located in the
Installation Manual.
LP (propane) gas is usually supplied as a liquid in
pressure tanks. 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 gen-
erator’s fuel solenoid valve may vary considerably,
depending on ambient temperatures. In cold weather,
supply pressures may drop to "zero". In warm weath-
er, extremely high gas pressures may be encoun-
tered. A primary/secondary supply regulator is
required to maintain correct gas supply pressure to
the generator demand regulator.
Minimum recommended gaseous fuel pressure at
the inlet side of the generator’s fuel solenoid valve is
Figure 1. Typical Prepackaged Installation
PART 1
Page 6
GENERAL INFORMATION
SECTION 1.2
PREPACKAGED INSTALLATION BASICS

GENERAL INFORMATION SECTION 1.2
PREPACKAGED INSTALLATION BASICS
PART 1
Page 7
11 inches water column for LP gas (6.38 ounces per
square inch), and 5 inches water column for natural
gas (2.89 ounces per square inch). The maximum
recommended pressure is 14 inches water column
(8.09 ounces per square inch). A primary regulator
may be 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 EQUIP-
MENT IS PLACED INTO SERVICE AND PERI-
ODICALLY THEREAFTER. PROCEDURES
USED IN GASEOUS FUEL LEAKAGE TESTS
MUST COMPLY STRICTLY WITH APPLICA-
BLE 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 genera-
tor 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 set-
tles. The flexible fuel line must be approved for use
with gaseous fuels.
!
VAPOR
LIQUID
LP PRIMARY/SECONDARY
SUPPLY REGULATOR
APPROVED FLEX LINE
(CAUTION! — KEEP FLEX FUEL LINE STRAIGHT)
11-14 INCHESWATER
COLUMN OPTIMUM
GENERATOR
DEMAND
REGULATOR
MANUAL SHUTOFF VALVE
GENERATOR BASE
GASCARBURETOR
Figure 3. Typical LP Gas Fuel System (Liquid Cooled Units)
NATURAL GAS
PRIMARY
REGULATOR
5-14 INCHESWATER COLUMN OPTIMUM
GENERATOR
DEMAND
REGULATOR
MANUAL SHUTOFF VALVE
GENERATOR BASE
GASCARBURETOR
APPROVED FLEX LINE
(CAUTION! — KEEP FLEX FUEL LINE STRAIGHT)
Figure 2. Typical Natural Gas Fuel System (Liquid Cooled Units)

THE TRANSFER SWITCH
A transfer switch is required by electrical code, to pre-
vent electrical feedback between the utility and stand-
by 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.
POWER SOURCE AND LOAD LINES
The utility power supply lines, the standby (generator)
supply lines, and electrical load lines must all be con-
nected to the proper terminal lugs in the transfer
switch. The following rules apply:
In 1-phase systems with a 2-pole transfer switch, con-
nect 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/T2 to the elec-
trical 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 ter-
minals: (a) utility 1, (b) utility 2, (c) load 1, (d) load 2,
(e) 23, and (f) 194. Prepackaged transfer switches
house an identically marked terminal board. Suitable,
approved wiring must be interconnected between
identically numbered terminals in the generator and
transfer switch. When these six terminals are properly
interconnected, dropout of utility source voltage below
a preset value will result in automatic generator start-
up 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. System control wiring must
be routed through its own separate conduit.
A control board, mounted on the standby generator
set, provides a "7-day exercise" feature. This feature
allows the standby generator to start and run once
every 7 days, on a day and at a time of day selected.
The timer clock that controls this automatic exercise
of the unit must be powered by voltage from the
transfer switch Load 1/Load 2 terminals. If the exer-
cise function is to be made available, connect suitable
wiring from the ATS transfer switch load terminal lugs,
to the "Load 1/Load 2" terminals in the generator.
The control board in the generator also provides a
battery "trickle charge" circuit. This circuit, when pow-
ered by utility source voltage, will deliver a charging
voltage to the battery during non-operating periods to
keep the battery charged. To use the trickle charge
feature, connect suitable wiring to the generator’s
"Utility 1/Utility 2" terminals and to the appropriate ter-
minals in the "ATS" transfer switch.
PART 1
Page 8
GENERAL INFORMATION
SECTION 1.2
PREPACKAGED INSTALLATION BASICS
- OPEN SWITCH TO TEST -
2A @ 250Vac MIN.
SWITCH TYPE, SPST
ELECTRICAL RATINGS,
UTILITY 1 (N1)
UTILITY 2 (N2)
LOAD 2 (T2)
23
194
CB1
NEUTRAL
CONNECTION
N1 N2
T1 T2
E1 E2
NEUTRAL
LUG
TRANSFER
SWITCH
UTILITY SUPPLY WITH
SERVICE DISCONNECT
LOAD
CUSTOMER
194
23
LOAD 2
UTILITY 2
UTILITY 1
AC GENERATOR
CONTROL PANEL
NOTE:
POWER LEADS AND
TRANSFER SWITCH
LEADS MUST BE
RUN IN TWO
DIFFERENT CONDUITS.
LOAD 1 (T1)
22
LOAD 1
REMOTE TEST
SWITCH (OPTIONAL)
11
44
33
Figure 4. Prepackaged Interconnection Diagram

GENERAL INFORMATION SECTION 1.3
PREPARATION BEFORE USE
PART 1
Page 9
GENERAL
The installer must ensure that the home standby gen-
erator has been properly installed. The system must
be inspected carefully following installation. All applic-
able 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 rec-
ommended oil.
• The engine cooling system must be properly ser-
viced with the recommended coolant.
FUEL REQUIREMENTS
Liquid cooled engine units are shipped from the facto-
ry to run on natural gas. The installer must ensure
that the correct fuel supply system has been installed
and is compatible with engine-generator require-
ments. Read "The Fuel Supply" in Section 1.3 careful-
ly.
ALL UNITS:
• 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
For prepackaged generators with liquid cooled
engine, use a high quality detergent oil that meets or
exceeds API Service SC, SD, SE or SF. Detergent
oils keep the engine cleaner and reduce carbon
deposits. Use oil having the following SAE viscosity
rating, based on the anticipated ambient temperature
range before the next oil change:
Engine crankcase oil capacities for the 1.5 Liter
engine covered in this manual can be found in the
specifications section at the beginning of the book.
RECOMMENDED ENGINE COOLANT
Use a mixture of 50 percent soft water and 50 percent
ethylene glycol base anti-freeze in the engine cooling
system. Use only SOFT WATER and LOW SILICATE
anti-freeze. If so equipped, a coolant recovery bottle
must also be properly serviced with the recommend-
ed 50-50 mixture. When adding coolant to the radiator
or to the coolant recovery bottle, use only the recom-
mended mixture.
If desired, a high quality rust inhibitor may be added
to the recommended coolant mixture.
CAUTION: Do NOT use any chromate base
rust inhibitor with ethylene glycol base anti-
freeze, or the formation of chromium hydrox-
ide (called "green slime") may result and
cause overheating of the engine. The use of
high silicate antifreeze boosters or additives
may also cause overheating. In addition, use
of any soluble oil type rust Inhibitor Is NOT
recommended.
!
AMBIENT TEMPERATURE
RANGE RECOMMENDED OIL
Above 80° F (27° C) SAE 30W or 15W-40
32° to 80° F (-1° to 27° C) SAE 20W-20 or 15W-40
Below 32° F (0° C) SAE 10W or 15W-40

VISUAL INSPECTION
When it becomes necessary to test or troubleshoot a
generator, it is a good practice to complete a thor-
ough 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 con-
nections.
• 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.
MEASURING VOLTAGES
When troubleshooting and testing the generator set,
the technician will be required to measure both AC
and DC voltages. Measurement of voltage requires
that the user be thoroughly familiar with the meter
being used for such tests. Consult the instruction
manual for the meter being used.
When measuring voltage, it is best to connect the
meter test leads to the terminals being tested while
the generator is shut down or while power to those
terminals is turned off.
DANGER: POWER VOLTAGES GENERATED
BY THIS EQUIPMENT ARE EXTREMELY HIGH
AND DANGEROUS. USE EXTREME CARE
WHEN MEASURING POWER VOLTAGES
SUCH AS GENERATOR AC OUTPUT VOLT-
AGE. CONTACT WITH LIVE TERMINALS AND
CONDUCTORS MAY RESULT IN HARMFUL
AND POSSIBLY LETHAL ELECTRICAL
SHOCK. DO NOT ATTEMPT TO READ
POWER VOLTAGES WHILE STANDING ON
WET OR DAMP GROUND, OR WHILE HANDS
OR FEET ARE WET. STAY WELL CLEAR OF
HIGH VOLTAGE POWER TERMINALS. CON-
NECT METER TEST LEADS TO TERMINALS
AND LEADS WHILE THE GENERATOR IS
SHUT DOWN OR WHEN THE POWER SUP-
PLY TO SUCH LEADS AND TERMINALS IS
TURNED OFF. THE USE OF INSULATIVE
RUBBER MATS IS RECOMMENDED. TAKE
POWER VOLTAGE READINGS ONLY WHILE
STANDING ON SUCH INSULATIVE MATS.
MEASURING CURRENT
Alternating current (AC) can be measured with a
clamp-on ammeter. Most clamp-on ammeters will not
measure direct current (DC). Load current readings
should never exceed the generator’s data plate rating
for continuous operation. However, momentary
surges in load current may be encountered when
starting electric motors.
On 1-phase generators, the data plate generally lists
rated line-to-line and line-to-neutral current.
MEASURING RESISTANCE
The resistance (in ohms) of generator stator and rotor
windings can be measured using an ohmmeter or an
accurate volt-ohm-milliammeter (VOM).
The resistance of some windings is extremely low.
Some readings are so low that a meter capable of
reading in the "milliohms" range would be required.
Many meters will simply read CONTINUITY.
However, a standard volt-ohm-milliammeter (VOM)
may be used to test for continuity, or for a shorted or
grounded condition.
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’s 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 mois-
ture that collects while the generator is shut down.
When problems are caused by moisture buildup on
the windings, they can usually be corrected by dry-
ing the windings. Cleaning and drying the windings
can usually eliminate dirt and moisture built up in the
generator windings.
!
PART 1 GENERAL INFORMATION
SECTION 1.4
TESTING, CLEANING AND DRYING
Page 10

GENERAL INFORMATION SECTION 1.4
TESTING, CLEANING AND DRYING
PART 1
Page 11
MEGGERS:
The normal resistance of generator winding insulation
is on the order of millions of ohms. This high resis-
tance can be measured with a device called a "meg-
ger". The megger is a megohm meter ("meg" stands
for million) and a power supply. The power supply
voltage varies between megger models and is selec-
table on some models. The most common power sup-
ply voltage is 500 volts. Use of power supplies
greater than 500 volts are not recommended on
prepackaged generators.
CAUTION: Before attempting to measure
Insulation resistance, first disconnect and
Isolate all leads of the winding to be tested.
Electronic components, diodes, surge pro-
tectors, 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 volt-
age 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 TESTS
GENERAL:
Units with liquid cooled engine and 1 -phase stator
windings are equipped with (a) dual stator AC power
windings, and (b) an excitation or DPE winding.
These units are not equipped with a battery charge
winding. Stator winding insulation tests consist of (a)
testing all windings to ground, (b) testing between iso-
lated windings, and (c) testing between parallel wind-
ings. Figure 3 represents the various stator AC output
leads on 1 -phase units with liquid-cooled engine.
TEST ALL WINDINGS TO GROUND:
1.Disconnect and isolate Stator Leads 11, 22, 33, 44,
2 and 6.
2.Connect terminal ends of all stator leads together.
Make sure all wire terminal ends are completely
isolated from frame ground.
3.Connect the red test probe of the Hi-Pot tester to
the terminal ends of all stator leads. Connect the
black tester probe to a clean frame ground on the
stator can. Then, proceed as follows:
a.Turn the Hi- Pot tester switch OFF
b.Plug the tester cord into a 120 volts AC wall
socket and set its voltage selector switch to
"500 volts".
c.Turn the tester switch ON and observe the
breakdown lamp. After one (1) second, turn the
tester switch OFF.
If the breakdown lamp turned on during the one (1)
second test, clean and dry the stator. Then, repeat
the test. If breakdown lamp comes on during the sec-
ond test, replace the stator assembly.
Figure 3. Stator Winding Leads (Liquid Cooled Units)
TEST BETWEEN ISOLATED WINDINGS:
1.Connect the red test probe to stator lead 2, the
black probe to stator lead 11.
2.Set the tester switch to "500 volts".
3.Turn the tester switch ON and check that the pilot
lamp is lighted.
4.Wait one (1) second while observing the tester
breakdown lamp. DO NOT EXCEED ONE SEC-
OND. After one (1) second, turn the tester switch
OFF.
5.Connect the red test probe to stator lead 2, the
black probe to stator lead 33. Then, repeat Steps 2,
3 and 4.
2
6
11
22
33
44
!

If the breakdown lamp turned on during any one (1)
second test, the stator should be cleaned and dried.
After cleaning and drying, repeat the test. If the break-
down lamp turns on during the second test, replace
the stator assembly.
TEST BETWEEN PARALLEL WINDINGS:
1 Set the tester’s voltage switch to "500 volts".
2.Connect the red tester probe to stator lead 11, the
black probe to stator lead 33.
3.Turn the tester switch ON and check that the pilot
lamp is on.
4.Waft one (1) second while observing the break-
down lamp. Then, turn the tester switch OFF.
If the breakdown lamp came on during the one (1)
second test, clean and dry the stator. Then, repeat
the test. If breakdown lamp comes on during second
test, replace the stator assembly.
TESTING ROTOR INSULATION
Before attempting to test rotor insulation, either the
brush leads must be completely removed from the
brushes or the brush holders must be completely
removed. The rotor must be completely isolated from
other components before starting the test.
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.
3.Turn the tester switch OFF.
4.Plug the tester into a 120 volts AC wall socket and
set the voltage switch to "500 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 insu-
lation breakdown test. If breakdown lamp comes on
during the second test, replace the rotor assembly.
Figure 6. 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 maxi-
mum).
CAUTION: Do not use sprayed water to clean
the generator. Some of the water will be
retained on generator windings and termi-
nals, and may cause very serious problems.
DRYING THE GENERATOR
To dry a generator, proceed as follows:
1.Open the generator main circuit breaker. NO ELEC-
TRICAL LOADS MUST BE APPLIED TO THE
GENERATOR WHILE DRYING.
2.Disconnect all wires No. 4 from the voltage regula-
tor.
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.
!
RED TEST LEAD
BLACK TEST LEAD
PART 1
Page 12
GENERAL INFORMATION
SECTION 1.4
TESTING, CLEANING AND DRYING

GENERAL INFORMATION SECTION 1.5
ENGINE-GENERATOR PROTECTIVE DEVICES
PART 1
Page 13
GENERAL
Standby electric power generators will often run unat-
tended for long periods of time. Such operating para-
meters as (a) engine oil pressure, (b) engine temper-
ature, (c) engine operating speed, and (d) engine
cranking and startup are not monitored by an operator
during automatic operation. Because engine opera-
tion 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 control 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, control board action will effect an
engine shutdown.
LOW OIL PRESSURE SHUTDOWN:
See Figure 1. Prepackaged generators with liquid
cooled engine are equipped with an oil pressure
switch having a closing pressure of about 10 psi.
Should oil pressure drop below that value, an auto-
matic engine shutdown will occur. Circuit operation is
similar to that of air-cooled units.
LOW COOLANT
LEVEL SWITCH
LOW OIL
PRESSURE
SWITCH
HIGH COOLANT
TEMPERATURE
SWITCH
OVERCRANK AND OVERSPEED
SHUTDOWN ARE CONTROLLED
BY THE CIRCUIT BOARD
Figure 1. Protective Devices on Liquid Cooled Engine

PART 1
Page 14
GENERAL INFORMATION
SECTION 1.5
ENGINE-GENERATOR PROTECTIVE DEVICES
HIGH COOLANT TEMPERATURE SHUTDOWN:
The engine is equipped with a coolant temperature
switch. Should engine coolant temperature exceed
approximately 284° F. (140° C.), the engine will be
shut down automatically by control board action.
LOW COOLANT LEVEL SENSOR:
It is possible that engine coolant level might drop low
enough so that the high temperature switch is no
longer immersed in the liquid coolant. If this happens
engine temperatures could increase rapidly but the
temperature switch would not sense the high temper-
ature condition and the engine would continue to run.
To prevent this occurrence, a low coolant level sensor
is provided. The sensor is immersed in cooling sys-
tem liquid. If coolant level drops below the level of the
low coolant level sensor, the device will complete a
Wire 85 circuit to ground. Engine shutdown will occur.
OVERSPEED SHUTDOWN:
The control board on liquid cooled units receives AC
frequency (rpm) signals directly from the stator AC
power windings, via sensing leads S15 and S16.
Should AC frequency exceed approximately 72 Hz,
circuit board action will initiate an automatic engine
shutdown.
NOTE: For units rated 1800 rpm, 72 Hz is equal to
2160 rpm.
NOTE: The control board also uses the sensing
lead signals (S15, S16) (a) to terminate cranking
at about 50% of rated frequency, and (b) as an
“engine running” signal. The circuit board will not
initiate transfer of electrical loads to the
"Standby" source until sensing voltage and fre-
quency is greater than 50 % of the unit’s rated
values.
OVERCRANK SHUTDOWN:
Automatic engine cranking and startup normally
occurs when the control 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 six (6) seconds. At the end
of six (6) seconds, control board action will energize a
crank relay and a run relay (both relays are on the
control board). On closure of the crank relay contacts,
control board action will deliver 12 volts DC to a con-
trol contactor (CC). The control contactor will ener-
gize and battery power will be delivered across its
closed contacts 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 imme-
diately when the switch is set to "Manual".
Control board action (during both a manual and an
automatic start) will hold the crank relay energized for
about 7-9 seconds. The relay will then de-energize for
about 7-9 seconds, and then energize again. In this
manner, the engine will be cranked for 7-9 seconds,
will rest for 7-9 seconds, and will crank again, and so
on until the engine starts.
If the engine has not started after approximately 90 sec-
onds of these crank-rest cycles, cranking will automati-
cally terminate and shutdown will occur. The control
board uses AC signals from the stator battery charge
windings as an indication that the engine has started.

Page 15
CONTROL PANEL
GENERAL:
See Figure 1 (Page 16). A typical prepackaged control
panel on units with liquid cooled engine includes: (a)
an auto-off-manual switch, (b) a fault indicator lamp,
(c) a 15 amp fuse, and (d) a set exercise switch.
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 moni-
tor 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.
FAULT INDICATOR LAMP:
The fault indicator lamp will turn on in the event that
any one or more of the following engine fault condi-
tions should occur: (a) low oil pressure, (b) high
coolant temperature, (c) low coolant level, (d) over-
speed, and (e) overcrank.
15 AMP FUSE:
This fuse protects the DC control system, including
the control board, against overload. If the fuse has
blown, engine cranking and running will not be possi-
ble. Should fuse replacement become necessary, use
only an identical 15 amp replacement fuse.
THE SET EXERCISE SWITCH:
Use this switch to select the time and day for system
exercise.
TO SELECT AUTOMATIC OPERATION
The following procedure applies to those installations
in which the prepackaged home standby generator is
installed in conjunction with a prepackaged transfer
switch. Prepackaged transfer switches do not have an
intelligence circuit of their own. Instead, automatic
operation on prepackaged transfer switch and gener-
ator combinations is controlled by a control circuit
board housed in the generator.
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 con-
tacts are at their “Utility” position, i.e., the load is connect-
ed to the utility power supply. If necessary, manually actu-
ate the switch main contacts to their “Utility” source side.
See Part 3 of this manual 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’s AUTO-OFF-MANUAL switch to its
AUTO position.
4. Actuate the generator’s 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" (genera-
tor) source and start the generator manually, proceed
!
GENERAL INFORMATION SECTION 1.6
OPERATING INSTRUCTIONS
PART 1

PART 1
Page 16
GENERAL INFORMATION
SECTION 1.6
OPERATING INSTRUCTIONS
as follows:
1.On the generator panel, set the AUTO-OFF-MANU-
AL 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.
5.On the generator panel, set the AUTO-OFF-MANU-
AL 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.
7.Set the generator’s 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’s 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’s 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” power source side, i.e., “Load” con-
nected to the “Utility” source.
6.Turn ON the “Utility” power supply to the transfer
switch, using whatever means provided.
7.Set the generator’s AUTO-OFF-MANUAL switch to
AUTO.
THE SET EXERCISE TIME SWITCH
The prepackaged home 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 opera-
tor. The set exercise time switch is provided to select
the day and time of day for system exercise.
See Part 5, Section 5.2 ("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 INSTRUC-
TIONS IN SECTION 1.6.
!
FUSE
15-A
AGC
FAULT
INDICATOR
AUTO
OFF
ON
SET
EXERCISE
TIME
MANUAL
HOURMETER
Figure 1. Control Panel