Generac Power Systems Guardian 004373-3 User manual

POWER SYSTEMS, INC.
®
®
Owner’s Manual
Liquid-cooled, Prepackaged
Standby Generators
Models:
004373-3 (40 kW/Single-phase w/ 200 Amp
Transfer Switch)
004626-2 (40 kW/Single-phase w/ 200 Amp
Transfer Switch California
Emissions)
ONLY QUALIFIED ELECTRICIANS OR CONTRACTORS
SHOULD ATTEMPT INSTALLATION!!
DANGER
*This manual should remain with the unit.

Generac®Power Systems, Inc.
INTRODUCTION
Thank you for purchasing the Guardian product line
by Generac Power Systems. This model is a compact,
high performance, liquid-cooled, engine-driven gen-
erator designed to automatically supply electrical
power to operate critical loads during a utility power
failure.
This unit is factory installed in an all-weather, metal
enclosure that is intended exclusively for outdoor
installation.
READ THIS MANUAL THOROUGHLY
If you do not understand any portion of this manual,
contact Generac or the nearest Generac/Guardian
Authorized Dealer for starting, operating and servicing
procedures.
Throughout this publication, and on tags and
decals affixed to the generator, DANGER, WARNING,
CAUTION and NOTE blocks are used to alert you to
special instruction about a particular operation that
may be hazardous if performed incorrectly or care-
lessly. Observe them carefully. Their definitions are as
follows:
After this heading, read instructions that, if not
strictly complied with, will result in personal injury
or property damage.
After this heading, read instructions that, if not
strictly complied with, may result in personal injury
or property damage.
After this heading, read instructions that, if not
strictly complied with, could result in damage to
equipment and/or property.
NOTE:
After this heading, read explanatory statements
that require special emphasis.
These safety warnings cannot eliminate the hazards
that they indicate. Common sense and strict compli-
ance with the special instructions while performing
the service are essential to preventing accidents.
Four commonly used safety symbols accompany the
DANGER, WARNING and CAUTION blocks. The type
of information each indicates is as follows:
This symbol points out important safety informa-
tion that, if not followed, could endanger personal
safety and/or property.
This symbol points out potential explosion hazard.
This symbol points out potential fire hazard.
This symbol points out potential electrical shock
hazard.
The operator is responsible for proper and safe use
of the equipment. Generac strongly recommends that
the operator read this Owner's Manual and thor-
oughly understand all instructions before using this
equipment. Generac also strongly recommends
instructing other users to properly start and operate
the unit. This prepares them if they need to operate
the equipment in an emergency.
CONTENTS
This manual contains pertinent owner’s information,
including warranty, electrical diagrams, exploded
views and lists of repair parts, for Guardian models:
004373-1 & 004626-0.
OPERATION AND MAINTENANCE
It is the operator's responsibility to perform all safety
checks, to make sure that all maintenance for safe
operation is performed promptly, and to have the
equipment checked periodically by a Generac/
Guardian Authorized Dealer. Normal maintenance
service and replacement of maintenance parts are the
responsibility of the owner/operator and, as such, are
not considered defects in materials or workmanship
within the terms of the warranty. Individual operating
habits and usage contribute to the need for mainte-
nance service.
Proper maintenance and care of the generator ensure a
minimum number of problems and keep operating
expenses at a minimum. See a Generac/Guardian
Authorized Dealer for service aids and accessories.
HOW TO OBTAIN SERVICE
When the generator requires servicing or repairs,
simply contact a Generac/Guardian Authorized
Dealer for assistance. Service technicians are factory-
trained and are capable of handling all service needs.
When contacting a Generac/Guardian Authorized
Dealer or the factory about parts and service, always
supply the complete model number and serial num-
ber of the unit as given on its data decal, which is
located on the generator.
Model No. ____________ Serial No. ______________
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AUTHORIZED
DEALER LOCATION
To locate the GENERAC/GUARDIAN AUTHORIZED
DEALER nearest you, please call this number:
1-800-333-1322
DEALER LOCATION INFORMATION
CAN BE OBTAINED AT THIS NUMBER.

Table of Contents
Guardian Liquid-cooled 40 kW Generator
Generac®Power Systems, Inc. 1
Introduction ......................Inside Front Cover
Read This Manual Thoroughly ......................IFC
Contents ........................................................IFC
Operation and Maintenance............................IFC
How to Obtain Service ....................................IFC
Authorized Dealer Locator Number ..................IFC
Safety Rules ......................................................2
Section 1 – General Information..................4
1.1 Unpacking/Inspection ..................................4
1.1.1 Lifting the Generator ........................4
1.2 The Generator..............................................4
1.3 Generator AC Connection Systems ..............4
1.4 Prepackaged Transfer Switch ......................4
1.5 Automatic System Operation........................4
1.6 Main Circuit Breaker ..................................5
1.7 Engine Protective Devices ............................5
1.7.1 Low Oil Pressure Switch ..................5
1.7.2 High Coolant
Temperature Switch ........................5
1.7.3 Low Coolant Level Switch ................5
1.7.4 Overspeed Shutdown ......................5
1.7.5 Overcrank Shutdown ......................5
1.7.6 DC Fuse............................................5
1.8 Specifications ..............................................5
1.8.1 Generator ........................................5
1.8.2 Engine ..............................................6
1.9 Fuel Requirements
and Recommendations ............................6
1.9.1 Conversion to LP Gas Vapor ............6
1.10 Engine Oil Recommendations ......................7
1.11 Coolant ........................................................7
1.12 Emission Control System ............................7
Section 2 – Installation ..................................8
2.1 Basic Standby Electric System ....................8
2.2 Emergency Circuit Isolation Method ............9
2.3 Total Circuit Isolation Method......................9
2.4 Grounding the Generator ............................9
2.5 Generator AC Neutral Connections ..............9
2.6 Transfer Switch Start Signal Connections....9
2.6.1 Pre-Packaged Type Switch ................9
2.6.2 “GTS” Type Switch ..........................9
2.7 Battery Installation ....................................10
2.7.1 Vented Batteries ............................10
2.8 Preparation Before Start-up ......................10
2.8.1 Prior to Initial Start-up ..................11
2.8.2 Transfer Switch..............................11
2.8.3 Fuel System ....................................11
2.8.4 Generator Set Lubrication..............11
2.8.5 Engine Coolant ..............................11
2.8.6 Belt Tension ..................................11
2.8.7 Electrical System............................11
2.8.8 Rodent Protection ..........................11
Section 3 – Operation ..................................12
3.1 Control Console Components ......................12
3.1.1 AC Voltmeter ..................................12
3.1.2 AC Ammeter ..................................12
3.1.3 AC Frequency Meter ......................12
3.1.4 DC Voltmeter..................................12
3.1.5 Hourmeter......................................12
3.1.6 Auto/Off/Manual Switch ..................12
3.1.7 Fault Indicator Lamp......................12
3.1.8 15-amp Fuse ..................................12
3.1.9 7.5 Amp Inline Fuse ......................12
3.1.10 Voltage-phase Selector Switch ........12
3.1.11 Set Exercise Time Switch ..............12
3.2 Using the Auto/Off/Manual Switch ..............12
3.2.1 “Auto” Position................................12
3.2.2 “Off” Position..................................13
3.2.3 “Manual” Position ..........................13
3.3 Automatic Transfer Operation....................13
3.4 Sequence of Automatic Operation ..............13
3.5 Engine Heater ..............................................13
3.6 Weekly Exercise Cycle ................................14
Section 4 – Maintenance ............................14
4.1 Checking the Engine Oil Level....................14
4.2 Changing the Engine Oil and Filter ............15
4.2.1 Engine Oil Recommendations ........15
4.2.2 Oil and Filter Change Procedure ......15
4.3 Changing the Engine Air Cleaner................15
4.4 Spark Plugs................................................16
4.5 Battery Maintenance ..................................16
4.5.1 Battery Replacement ......................16
4.6 Cooling System ..........................................17
4.7 Overload Protection for
Engine DC Electrical System......................17
4.8 DC Fuse ....................................................17
4.9 Engine Coolant ..........................................17
4.10 Miscellaneous Maintenance ........................17
4.10.1 Cleaning the Generator ..................17
4.10.2 Rodent Protection ..........................17
4.11 Out of Service Procedure ..........................18
4.11.1 Removal From Service....................18
4.11.2 Return to Service............................18
4.12 Service Schedule ........................................19
Section 5 – Troubleshooting ......................20
Section 6 – Electrical Data ..........................21
Section 7 – Exploded Views and
Parts Lists ..................................30
Section 8 – Notes ..........................................59
Section 9 – Warranty ....................................60

2 Generac®Power Systems, Inc.
Study these SAFETY RULES carefully before installing,
operating or servicing this equipment. Become familiar
with this Owner’s Manual and with the unit. The gen-
erator 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 fun-
damental rules or precautions.
Generac cannot possibly anticipate every possible
circumstance that might involve a hazard. The warn-
ings in this manual, and on tags and decals
affixed to the unit are, therefore, not all-inclusive. If you
use a procedure, work method or operating technique
Generac does not specifically recommend, you must
satisfy yourself that it is safe for you and others. You
also must make sure the procedure, work method or
operating technique that is chosen does not render the
generator unsafe.
Despite the safe design of this generator,
operating this equipment imprudently, neglecting its
maintenance or being careless can cause possible
injury or death. Permit only responsible and capable
persons to 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 gen-
erators.
GENERAL HAZARDS
• For safety reasons, Generac recommends that the
installation, initial start-up and maintenance of this
equipment is carried out by a Generac/Guardian
Authorized Dealer.
• 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 gener-
ator is installed, operated and serviced in accordance
with the manufacturer’s instructions and recommen-
dations. Following installation, do not do anything
that might render the unit unsafe or in noncompli-
ance with the aforementioned codes, standards, laws
and regulations.
• The engine exhaust fumes contain carbon monoxide,
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 in any room or building housing the gen-
erator to prevent buildup of explosive gases and to
ensure correct generator operation. Do not alter the
installation or permit even partial blockage of ventila-
tion provisions, as this can seriously affect safe oper-
ation of the generator.
• Keep the area around the generator clean and unclut-
tered. Remove any materials that could become haz-
ardous.
• When working on this equipment, remain alert at all
times. Never work on the equipment when you are
physically or mentally fatigued.
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DANGER
Important Safety Instructions
Guardian Liquid-cooled 40 kW Generator
SAVE THESE INSTRUCTIONS – The manufacturer suggests that these rules for safe
operation be copied and posted in potential hazard areas. Safety should be stressed to all
operators and potential operators of this equipment.
!
The engine exhaust from this product
contains chemicals known to the state
of California to cause cancer, birth
defects or other reproductive harm.
WARNING:
!!
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SAVE THESE INSTRUCTIONS – This manual contains important instructions that should be
followed during installation and maintenance of the generator and batteries.
!
!
This product contains or emits chemicals
known to the state of California to cause
cancer, birth defects or other reproductive harm.
WARNING:
!!

Generac®Power Systems, Inc. 3
• 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 accidental
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 dan-
gerous electrical voltages and can cause fatal electri-
cal shock. Utility power delivers extremely high and
dangerous voltages to the transfer switch as does the
standby generator when it is in operation. Avoid con-
tact with bare wires, terminals, connections, etc.,
while the unit is running. Ensure all appropriate cov-
ers, guards and barriers are in place before operating
the generator. If work must be done around an oper-
ating 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.
• The National Electrical Code (NEC) 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 condition 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 elec-
trical current (ampacity) to which they will be sub-
jected to.
• Before installing or servicing this (and related) equip-
ment, 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 genrator electric
system from the utility electric system while in oper-
ation. 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 automatically 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 automatic
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, immedi-
ately 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
rope or board, to free the victim from the live con-
ductor. 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 electric
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 extinguishers,
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 combustible
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 sev-
eral types of fuels. All fuel types are potentially FLAM-
MABLE and/orEXPLOSIVE and should be handled
with care. Comply with all laws regulating the stor-
age and handling of fuels. Inspect the unit’s fuel sys-
tem frequently and correct any leaks immediately.
uel 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.
Important Safety Instructions
Guardian Liquid-cooled 40 kW Generator

4 Generac®Power Systems, Inc.
1.1 UNPACKING/INSPECTION
After unpacking, carefully inspect the contents for dam-
age.
• This standby generator set has been factory installed
in an all-weather, metal enclosure that is intended
exclusively for outdoor installation.
If this generator is used to power electrical load
circuits normally powered by a utility power
source, code requires to install a transfer switch.
The transfer switch must effectively isolate the
electrical system from the utility distribution sys-
tem when the generator is operating (NEC 701).
Failure to isolate an electrical system by such
means will result in damage to the generator and
also may result in injury or death to utility power
workers due to backfeed of electrical energy.
If any loss or damage is noted at time of delivery, have
the person(s) making the delivery note all damage on
the freight bill or affix his or her signature under the
consignor's memo of loss or damage.
If there is loss or damage after delivery, separate the
damaged materials and contact the carrier for claim
procedures.
“Concealed damage” is understood to mean damage to
the contents of a package that is not in evidence at the
time of delivery, but is discovered later.
1.1.1 LIFTING THE GENERATOR
When lifting or hoisting equipment is used, be
careful not to touch overhead power lines.
The generator’s weight of more than 2,000
pounds requires proper tools and equipment, and
qualified personnel to be used in all phases of
handling and unpacking.
1.2 THE GENERATOR
This liquid-cooled, Guardian generator set is designed
to supply electrical power to operate critical electrical
loads during utility power failure. Use this generator as
a source of electrical power for the operation of 120
and/or 240-volt, single-phase loads.
1.3 GENERATOR AC
CONNECTION SYSTEMS
Figure 1.1 represents a single-phase, four-wire genera-
tor AC connection system. The stator assembly in this
system consists of a pair of stationary windings with
two leads brought out of each winding. Each single
winding can supply a 120-volt, 60-Hertz AC output.
When the two windings are connected in series, a 240-
volt, 60-Hertz AC output results. Typically, the two “hot”
leads in the circuit are Wires 11 and 44. The neutral
leads are the junction of Wires 22 and 33.
Figure 1.1 – Single-phase
Generator AC Connection System
1.4 PREPACKAGED TRANSFER SWITCH
The transfer switch shipped with this generator is rated
200 amps maximum at 120/240 volts AC single-phase.
The enclosure of the transfer switch is NEMA 3R. This
type of enclosure is intended for indoor or outdoor use.
Follow these rules:
• Install the transfer switch on a firm, sturdy support-
ing structure.
• To prevent switch distortion, level the switch if nec-
essary. This can be done by placing washers
between the switch enclosure and mounting surface.
• Never install the switch where any corrosive sub-
stance might drop onto the enclosure.
• Where practical, protect the switch against excessive
moisture, dust, dirt, lint, and construction grit.
Always prevent corrosive vapors from coming in con-
tact with enclosure.
1.5 AUTOMATIC SYSTEM OPERATION
When this generator, along with its transfer switch, has
been installed and interconnected, a circuit board in the
generator panel continuously monitors utility power
source voltage. Should that voltage drop below a preset
value, and remain at such a low state for a preset amount
of time, the generator cranks and starts. After the gener-
ator starts, the transfer switch transfers load circuits so
the generator can power them.
When utility source voltage has been restored, the
switch transfers back to the utility source voltage, and
the generator then shuts down after a brief cool-down
time.
Neutral Block
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Section 1 — General Information
Guardian Liquid-cooled 40 kW Generator

1.6 MAIN CIRCUIT BREAKER
The generator’s main circuit breaker is included with the
unit as shipped from the factory. The breaker for each
unit is described as follows:
1.7 ENGINE PROTECTIVE DEVICES
The engine has several safety switches that cause
it to automatically shut down under the following condi-
tions: low oil pressure, high coolant temperature, low
coolant level, engine overspeed and overcrank.
1.7.1 LOW OIL PRESSURE SWITCH
This switch is normally closed (N.C.) but is held open by
engine oil pressure during engine running. Should oper-
ating oil pressure drop below approximately 10 psi (68
kPa), the switch contacts close, and the engine shuts down
automatically (Figure 1.2).
Figure 1.2 – Engine Protective Devices
1.7.2 HIGH COOLANT TEMPERATURE SWITCH
This normally open (N.O.) thermostatic switch has a
sensing tip that is immersed in captive coolant. Should
the coolant temperature exceed approximately 121° C
(250° F), the switch contacts close, which causes the
engine to shut down automatically (Figure 1.2).
1.7.3 LOW COOLANT LEVEL SWITCH
Should the engine coolant level drop below the level of the
high coolant temperature switch, it is possible for the
engine to overheat without automatic shut down. To pre-
vent such overheating without automatic shut down, the
engine has a low coolant level sensor. If the engine coolant
drops too low, the engine automatically shuts down
(Figure 1.2).
1.7.4 OVERSPEED SHUTDOWN
The control module assembly (CMA) circuit board on
liquid-cooled units receives AC frequency (rpm) signals
directly from the stator AC power windings. Should AC
frequency exceed approximately 72 Hertz, circuit board
action will automatically shut down the engine.
1.7.5 OVERCRANK SHUTDOWN
After 90 seconds of crank-rest cycles (about seven sec-
onds cranking/seven seconds at rest), this function ends
cranking if the engine fails to start in that 90-second
span.
1.7.6 DC FUSE
This fuse is located on the front panel of the control sys-
tem. It protects the panel wiring and components from
damaging overload. Always remove this fuse before
commencing work on the generator. The unit will not
start or crank if the fuse is blown. Replace the fuse with
one of the same size, type, and rating. Generac uses an
AGC fuse rated at 15 amps.
1.8 SPECIFICATIONS
1.8.1 GENERATOR
Models ..........................................004373-3 & 004626-2
Rated Maximum Continuous
AC Power Output (kW)*..................................................40
Rated Voltage (volts) ................................................120/240
Rated Maximum Continuous
Current at 240 Volts, Single-phase (amps)................................167
Number of Rotor Poles ........................................................4
Driven Speed of Rotor (rpm) ........................................1,800
Type of Stator ........................................................Four-wire
Rotor Excitation System ..................................Direct Excited
Brush-type System
Stator Insulation ....................................................Class “H”
Rotor Insulation ......................................................Class “F”
*Rated power of generator is subject to and limited by such factors as ambient tempera-
ture, altitude, engine condition and other factors. Engine power will decrease about 3.5
percent for each 1,000 feet above sea level; and also will decrease an additional 1 percent
for each 6° C (10° F) above 15.5° C (60° F) ambient. Maximum output power of the gener-
ator is limited by maximum engine power.
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Section 1 — General Information
Guardian Liquid-cooled 40 kW Generator
Generac®Power Systems, Inc. 5
Model Number Circuit Breaker Rating
004373-3 200-amp breaker
004626-2 200-amp breaker

6 Generac®Power Systems, Inc.
1.8.1 Generator and Load Compatibility
The generator must be fully compatible with the rated
voltage, number of phases and frequency of the con-
nected electrical loads. The generator, connected elec-
trical devices, or both, can be damaged if voltage, num-
ber of phases and frequency are not compatible.
NOTE:
This manual assumes that the standby generator has
been properly selected, installed and interconnected
by a competent, qualified electrician or installation
contractor. Once the installation is complete, do
nothing that may result in noncompatibility between
the generator and connected electrical loads.
1.8.2 ENGINE
Make........................................................General Motors
Displacement ................................4.3 liters (262 cu. in.)
Cylinder Arrangement ................................................V-6
Valve Arrangement..................................Overhead Valves
Firing Order ..................................................1-6-5-4-3-2
Number of Main Bearings ..............................................4
Compression Ratio ..............................................9.4-to-1
No. of Teeth on Flywheel ............................................168
Ignition System ................................................Electronic
Ignition Timing at 1,800 rpm ..............40 degrees BTDC
Rated Horsepower at 1,800 rpm..................................67
Spark Plug Gap ..............................0.045 inch (1.1 mm)
Recommended Spark Plugs ......AC 41-932 or equivalent
Oil Pressure ......................................................30-50 psi
Crankcase Oil Capacity ..............4.5 U.S. quarts (4.25 L)
Recommended Engine Oil ............................SAE 15W-40
Type of Cooling System ......Pressurized, closed recovery
Cooling Fan ..................................................Pusher Type
Cooling System Capacity ..............4.5 U.S. gallons (17 L)
Recommended Coolant ..................Use a 50-50 mixture of
ethylene glycol and soft water.
Fuel Consumption
Natural Gas
004373-3 & 004626-2 ........................................720 cfh
LP Gas
004373-3 & 004626-2..............................288 cfh/7.9gph
1.9 FUEL REQUIREMENTS
AND RECOMMENDATIONS
With LP gas, use only the vapor withdrawal system. This
type of system uses the vapors formed above the liquid
fuel in the storage tank.
Recommended fuels should have a Btu content of at
least 1,000 Btus per cubic foot for natural gas; or at
least 2,520 Btus per cubic foot for LP gas. Ask your fuel
supplier for the Btu content of your fuel.
Fuel pressure for both natural gas and liquid propane
setups should be 11 inches to 14 inches of water column
(0.6 psi) at all load ranges.
Gaseous fuels such as natural gas and liquid
propane (LP) gas are highly explosive. Even the
slightest spark can ignite such fuels and cause an
explosion. No leakage of fuel is permitted. Natural
gas, which is lighter than air, tends to collect in
high areas; LP gas is heavier than air and tends to
settle in low areas – install leak detectors accord-
ingly.
1.9.1 CONVERSION TO LP GAS VAPOR
The generator is shipped from the factory configured for
using natural gas as fuel. To convert the fuel system to LP
gas, proceed as follows (Figure 1.3).
1. Remove end cap from the pressure reducer valve.
2. Turn the tension screw counterclockwise until all ten-
sion is removed from the inner spring.
3. Install and tighten the end cap.
4. Invert the pressure reducer valve. In other words, turn
it upside down (end cap facing downward).
5. Purge and leak test the entire fuel system according to
gaseous fuel codes. NO LEAKS can appear at any point
in the system.
Figure 1.3 – Conversion to LP Gas Vapor
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Section 1 — General Information
Guardian Liquid-cooled 40 kW Generator

1.10 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 CC, SD, SE or SF.” Detergent oils keep the
engine cleaner and reduce carbon deposits. Use oil hav-
ing the following SAE viscosity rating, based on the
ambient temperature range anticipated before the next
oil change:
Any attempt to crank or start the engine before it
has been properly serviced with the recommended
oil may result in an engine failure.
1.11 COOLANT
Use a mixture of half low silicate, ethylene glycol base
antifreeze and half soft water. Use only soft water and
only low silicate antifreeze. If desired, add a high quali-
ty rust inhibitor to the recommended coolant mixture.
When adding coolant, always add the recommended 50-
50 mixture.
Do not remove the radiator pressure cap while
the engine is hot or serious burns from boiling
liquid or steam could result.
Ethylene glycol base antifreeze is poisonous. Do
not use mouth to siphon coolant from the radia-
tor, recovery bottle or any container. Wash
hands thoroughly after handling. Never store
used antifreeze in an open container because
animals are atracted to the smell and taste of
antifreeze even though it is poisonous to them.
Do not use any chromate base rust inhibitor
with ethylene glycol base antifreeze, or chromi-
um hydroxide (“green slime”) will form and
cause overheating. Engines that have been
operated with a chromate base rust inhibitor
must be chemically cleaned before adding ethyl-
ene glycol base antifreeze. Using any high sili-
cate antifreeze boosters or additives also will
cause overheating. Generac also recommends
that any soluble oil inhibitor NOT be used for
this equipment.
1.12 EMISSIONS CONTROL SYSTEM
(MODEL 004626-2)
This model is equipped with an active exhaust emis-
sions control system to comply with certain California
air district regulations for natural gas emergency gener-
ating sets, including the South Coast Air Quality
Management District. Do not tamper with or disable
any part of this system, including the exhaust catalyst,
carburetor, oxygen sensor, air-fuel ratio controller, sole-
noid valve and gas regulator. These items are not sub-
ject to periodic maintenance or adjustment.
This model is of a size (greater than 50 brakehorse-
power) that may require a review by air permitting
authorities prior to installation and operation. Consult
the local air management district for details and spe-
cific requirements.
Figure 1.4 - Emissions Control System
1.12.1 AIR FUEL RATIO CONTROLLER
The air fuel ratio controller is an advanced micro-
processor designed to work with a three-way catalyst
and a feedback (rich bias) carburetor to provide close-
loop fuel management. Its digital adaptive control is
able to compensate for variations in fuel mixtures and
engine tunes. It is time based activated. (For example, it
will activate after 45 seconds from receiving the power
signal.) The part number for the air fuel ratio controller
is 0D4221.
Principle of Operation: The oxygen sensor, installed
on the exhaust pipe, between the engine and the cat-
alytic muffler (closer to the engine), continuously moni-
tors the exhaust gas composition. A feedback signal is
sent from the oxygen sensor to the air fuel ratio con-
troller, which controls the fuel system to maintain the
optimal, stoichiometric air fuel ratio. The air fuel mix-
ture to the engine is controlled by biasing the
diaphragm in the fuel regulator using vacuum (from the
carburetor). This vacuum signal is directed to the fuel
regulator via the control valve. The air fuel ratio con-
troller determines the amount of vacuum signal sent to
the fuel regulator. The more vacuum sent to the regula-
tor, the more restricted the fuel flow will be, therefore
the leaner the air fuel mixture.
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Section 1 — General Information
Guardian Liquid-cooled 40 kW Generator
Generac®Power Systems, Inc. 7
Temperature Oil Grade(Recommended)
Above 80º F (27º C) SAE 30W or 15W-40
32º to 80º F (-1º C to 27º C) SAE 20W-20 or 15W-40
Below 32º F (0º C) SAE 10W or 15W-40

8 Generac®Power Systems, Inc.
If an open bottom is used, the engine-generator is
to be installed over non-combustible materials
and should be located such that combustible
materials are not capable of accumulating under
the generator set.
Only qualified, competent installation contractors or
electricians thoroughly familiar with applicable codes,
standards and regulations should install this standby
electric power system. The installation must comply
strictly with all codes, standards and regulations per-
taining to the installation.
After the system has been installed, you must not do
anything that might render the installation in noncom-
pliance with such codes, standards and regulations.
NOTE:
For more information about the installation of a stand-
by system, you can order Engine-Generator Standby
Electric Power Systems Installer’s Guide and
Reference Manual (part #046622) from a Generac
Authorized Service Dealer.
NFPA STANDARDS
The following published standards booklets pertaining
to standby electric systems are available form the
National Fire Protection Association (NFPA),
Batterymarch Park, Quincy, MA 02269:
• NFPA No. 37, STATIONARY COMBUSTION ENGINES
AND GAS TURBINES.
• NFPA No. 76A, ESSENTIAL ELECTRICAL SYSTEMS
FOR HEALTH CARE FACILITIES.
• NFPA No. 220, STANDARD TYPES OF BUILDING
CONSTRUCTION
• NFPA No. 68, GUIDE FOR EXPLOSION VENTING
• NFPA No. 70, NATIONAL ELECTRICAL CODE.
• NFPA No. 30, FLAMMABLE AND COMBUSTIBLE
LIQUIDS CODE.
• NFPA No. 10, INSTALLATION, MAINTENANCE AND
USE OF PORTABLE FIRE EXTINGUISHERS.
OTHER PUBLISHED STANDARDS
In addition to NFPA standards, the following informa-
tion pertaining to the installation and use of standby
electric systems is available:
• Article X, NATIONAL BUILDING CODE, available
from the American Insurance Association, 85 John
Street, New York, N.Y. 10038.
• AGRICULTURAL WIRING HANDBOOK, obtainable
from the Food and Energy Council, 909 University
Avenue, Columbia, MO, 65201.
• ASAE EP-364.2, INSTALLATION AND MAINTE-
NANCE OF FARM STANDBY ELECTRIC POWER,
available from the American Society of Agricultural
Engineers, 2950 Niles Road, St. Joseph, MI 49085.
• A52.1, AMERICAN NATIONAL STANDARD FOR
CHIMNEYS, FIREPLACES AND VENTING SYS-
TEMS, available from the American National
Standard Institute, 1430 Broadway, New York, N.Y.
10018.
• NEC HANDBOOK available from the National Fire
Protection Association, 1 Batterymarch Park,
PO Box 9146, Quincy, MA 02269-9959.
2.1 BASIC STANDBY ELECTRIC SYSTEM
Figure 2.1 shows a schematic diagram of a basic stand-
by electric system. Both the UTILITY power supply and
the STANDBY (generator) output are connected to an
approved transfer switch. The transfer switch is
required by electrical code and serves the following
functions:
• Permits the LOAD circuits to be connected to only one
power supply at a time.
• Prevents electrical backfeed between STANDBY
power and the UTILITY power circuits.
Notice that both the STANDBY and the UTILITY power
supplies to the transfer switch are protected against
overload by a main line circuit breaker.
NOTE:
Generac recommends the use of a Generac Power
Systems “pre-packaged” type transfer switch (Part
No. 0D4406) in conjunction with this generator.
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Section 2 — Installation
Guardian Liquid-cooled 40 kW Generator
STANDBY GENERATOR INSTALLATION
Connecting this generator to an electrical system normally supplied by an electric utility shall be by
means of a transfer switch (such as the Generac “GTS” type transfer switch), so as to isolate the electric
system from the utility distribution system when the generator is operating. Failure to isolate the
electric system by these means will result in damage to the generator and may also result in injury
or death to utility workers due to backfeed of electrical energy.
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Generac®Power Systems, Inc. 9
Figure 2.1 – Basic Standby Electric System
2.2 EMERGENCY CIRCUIT ISOLATION
METHOD
This prevents overloading the generator by keeping elec-
trical loads below the wattage/amperage capacity of the
generator. If the generator is powering only critical
loads, within its wattage/amperage capacity, during util-
ity power outages, consider using the emergency circuit
isolation method.
Critical electrical loads are grouped together and wired
into a separate “Emergency Distribution Panel.” Load
circuits powered by that panel are within the
wattage/amperage capacity of the generator set. When
this method is used, it is difficult to overload the gener-
ator. The transfer switch must meet the following
requirements:
• It must have an ampere rating equal to or greater
than the total amperage rating of the emergency dis-
tribution panel circuit.
• It must be installed between the building’s main distri-
bution panel and the emergency distribution panel.
2.3 TOTAL CIRCUIT ISOLATION METHOD
When a generator capable of powering all electrical
loads in the circuit is to be installed, use the “Total
Circuit Isolation Method.” It is possible for the genera-
tor to be overloaded when this isolation method is
employed. The following apply to the transfer switch in
this type of system.
• Ampere rating of the transfer switch must be equal to
or greater than the ampere rating of the normal
incoming utility service.
• The transfer switch must be installed between the
utility service entrance and the building distribution
panel.
2.4 GROUNDING THE GENERATOR
The National Electrical Code requires the frame and
external electrically conductive parts of this equipment
to be properly connected to an approved earth ground
and/or grounding rods. For that purpose, a GROUND
LUG (Figure 2.2) is provided on the generator mounting
base. Consult a qualified electrician for grounding
requirements in your area. Grounding procedures must
meet local regulations.
Do not connect the ground wire to any pipe that
carries a flammable or explosive substance – FIRE
or an EXPLOSION may result.
Proper grounding helps protect personnel against electri-
cal shock in the event of a ground fault condition in the
generator or in connected electrical devices. In addition,
grounding helps dissipate static electricity that often
builds up in ungrounded devices.
Figure 2.2 – Generator Grounding Lug (typical)
2.5 GENERATOR AC NEUTRAL
CONNECTIONS
Generac uses an UNGROUNDED AC neutral. Grounding
is recommended only at the main service entrance.
2.6 TRANSFER SWITCH START SIGNAL
CONNECTIONS
2.6.1 PRE-PACKAGED TYPE SWITCH
Connect the six signal wires from the automatic trans-
fer switch to the engine generator control, which is
located on the upper right side and inside the lower
control panel. Match wires 23, 194, N1, N2, T1 and T2
in the transfer switch to the corresponding wires on the
terminal strip in the lower panel. The conductors for
these wires should be in a seperate conduit from the
main AC output wires. If the control wires are run in the
same conduit, the control wires must be a shielded
cable.
2.6.2 “GTS” Type Engineered Switch
Connect the two-wire start signal from the automatic
transfer switch to the automatic start connection, which is
located in the right hand corner inside the lower panel.
Match wires 178 and 183 in the transfer switch to 178
and 183 on the terminal strip in the control panel. The
conductors for the two-wire start circuit must be in their
own conduit. If the control wires are run in the same
conduit, the control wires must be a shielded cable.
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Section 2 — Installation
Guardian Liquid-cooled 40 kW Generator

10 Generac®Power Systems, Inc.
NOTE:
When using a GTS switch, it is necessary to connect
a 240V AC supply to N1 and N2 terminals
of the generator to provide for battery charging.
Wires T1, T2, 23 and 194 should not be
connected.
2.7 BATTERY INSTALLATION
Standby generators installed with automatic trans-
fer switches will crank and start automatically
when normal (utility) source voltage is removed or
is below an acceptable preset level. To prevent
such automatic start-up and possible injury to per-
sonnel, do not connect battery cables until the
normal source voltage at the transfer switch is cor-
rect and the system is ready to be placed into
operation.
Storage batteries give off explosive hydrogen gas.
This gas can form an explosive mixture around
the battery for several hours after charging. The
slightest spark can ignite the gas and cause an
explosion. Such an explosion can shatter the bat-
tery and cause blindness or other injury. Any area
that houses a storage battery must be properly
ventilated. Do not allow smoking, open flame,
sparks or any spark producing tools or equipment
near the battery.
Battery electrolyte fluid is an extremely caustic
sulfuric acid solution that can cause severe burns.
Do not permit fluid to contact eyes, skin, clothing,
painted surfaces, etc. Wear protective goggles,
protective clothing and gloves when handling a
battery. If fluid is spilled, flush the affected area
immediately with clear water.
Do not dispose of the battery in a fire. The
battery is capable of exploding.
Do not open or mutilate the battery. Released
electrolyte can be toxic and harmful to the skin
and eyes.
The battery represents a risk of high short circuit
current. When working on the battery, always
remove watches, rings or other metal objects, and
only use tools that have insulated handles.
2.7.1 VENTED BATTERIES
The electrolyte is a dilute sulfuric acid that is
harmful to the skin and eyes. It is electrically con-
ductive and corrosive. The following procedures
are to be observed:
• Wear full eye protection and protective clothing,
• Where electrolyte contacts the skin, wash it off
immediately with water,
• Where electrolyte contacts the eyes, flush thoroughly
and immediately with water and seek medical atten-
tion, and
• Spilled electrolyte is to be washed down with an acid-
neutralizing agent. A common practice is to use a
solution of one pound (500 grams) bicarbonate of
soda to one gallon (4 liters) of water. The bicarbonate
of soda solution is to be added until the evidence of
reaction (foaming) has ceased. The resulting liquid is
to be flushed with water and the area dried.
Lead acid batteries present a risk of fire because
they generate hydrogen gas. The following proce-
dures are to be followed:
• DO NOT SMOKE when near batteries,
• DO NOT cause flame or spark in battery area, and
• Discharge static electricity from body before touching
batteries by first touching a grounded metal surface.
Servicing of batteries is to be performed or supervised
by personnel knowledgeable of batteries and the
required precautions. Keep unauthorized personnel
away from batteries.
For recommended batteries, see “Battery Maintenance”
page 16. All batteries must be at 100 percent state-of-
charge before they are installed on the generator.
When using maintenance-free batteries, it is not neces-
sary to check the specific gravity or electrolyte level.
Have these procedures performed at the intervals spec-
ified in Section 4, “Maintenance.” A negative ground sys-
tem is used. Battery connections are shown on the
wiring diagrams. Make sure all batteries are correctly
connected and terminals are tight. Observe battery
polarity when connecting batteries to the generator set.
NOTE:
Damage will result if the battery connections are
reversed.
2.8 PREPARATION BEFORE START-UP
The instructions in this section assume that the standby
generator has been properly installed, serviced, tested,
adjusted and otherwise prepared for use by a competent,
qualified installation contractor. Be sure to read the
“Safety Rules” on Pages 2 and 3, as well as all other safe-
ty information in this manual, before attempting to oper-
ate this (and related) equipment.
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Section 2 — Installation
Guardian Liquid-cooled 40 kW Generator

2.8.1 PRIOR TO INITIAL START-UP
Prior to initially starting the generator, it must be
properly prepared for use. Any attempt to crank
or start the engine before it has been properly
serviced with the recommended types and quanti-
ties of engine fluids (oil, coolant, fuel, etc.) may
result in an engine failure.
Before starting the generator for the first time, the
installer must complete the following procedures. For
follow-up maintenance information and/or service inter-
vals, please refer to Section 4, “Maintenance.”
2.8.2 Transfer Switch
If this generator is used to supply power to any electri-
cal system normally powered by an electric utility, the
National Electrical Code requires that a transfer switch
be installed. The transfer switch prevents electrical
backfeed between two different electrical systems. (For
additional information, see the applicable transfer
switch manual for this unit.) The transfer switch, as
well as the generator and other standby components,
must be properly located and mounted in strict compli-
ance with applicable codes, standards and regulations.
2.8.3 Fuel System
Make sure the fuel supply system to the generator (a)
delivers the correct fuel at the correct pressure and (b)
is properly purged and leak tested according
to code. No fuel leakage is permitted. See
“Specifications” (Page 6) for more information.
2.8.4 Generator Set Lubrication
Check the engine crankcase oil level before operating
and add oil to the proper level – the dipstick “FULL”
mark. Never operate the engine with the oil level below
the dipstick “ADD” mark. See “Specifications” (Page 5)
and “Engine Oil Recommendations” (Page 7).
NOTE:
This engine is shipped from the manufacturer with
SAE 15W-40 oil. This oil should be changed after 30
hours of operation.
2.8.5 Engine Coolant
Have the engine cooling system properly filled with the
recommended coolant mixture. Check the system for
leaks and other problems. See “Specifications” (Page 5)
and “Coolant” (Page 7).
2.8.6 Belt Tension
Check the engine fan belt tension and condition prior to
placing the unit into service and at recommended
intervals. Belt tension is correct when a force of approx-
imately 22 pounds (10 kg), applied midway between
pulleys, deflects the belt about 3/8- to 5/8-inch (10 to 16
mm).
2.8.7 Electrical System
Make sure the generator is properly connected to an
approved earth ground and/or ground rod.
Make sure the generator battery is fully charged, proper-
ly installed and interconnected, and ready for use.
Check to ensure that there are no loose electrical con-
nections. Restrain any loose wires to keep them clear of
any moving generator set components.
2.8.8 Rodent Protection
Make sure the four 3-inch diameter cap plugs (part #
0A8785) are properly installed in the tie-down holes in
the side rails of the unit’s base frame (Figure 2.3). The
cap plugs are shipped in a plastic bag located in the
lower connection box. These plugs are needed to pre-
vent rodents from accessing the interior of the genera-
tor set. On acoustic units, cap plugs also are needed to
stay within noise specification limits.
Figure 2.3 - Base Frame Cap Plugs
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Section 2 — Installation
Guardian Liquid-cooled 40 kW Generator
Generac®Power Systems, Inc. 11

12 Generac®Power Systems, Inc.
3.1 CONTROL CONSOLE COMPONENTS
The components of a liquid-cooled generator control
console (Figure 3.1) are as follows:
Figure 3.1 – Control Console
3.1.1 AC VOLTMETER
The voltmeter displays generator AC output voltage dur-
ing operation. Voltage is regulated by a solid-state volt-
age regulator and is proportional to AC frequency. Refer
to the unit’s DATA PLATE for rated AC voltage.
3.1.2 AC AMMETER
This indicates current draw of connected electrical
loads during operation. DO NOT EXCEED THE UNIT’S
RATED MAXIMUM CONTINUOUS CURRENT. Refer to
the unit DATA PLATE.
3.1.3 AC FREQUENCY METER
This indicates generator AC output frequency in Hertz
(cycles per second). Frequency is proportional to engine
speed. Units with a four-pole rotor, supply 60 Hertz at
1,800 rpm. The frequency reading with no electrical
loads connected (no-load condition) should be between
60-62 Hertz.
3.1.4 DC VOLTMETER
The generator is equipped with a belt-driven DC alter-
nator, which maintains battery state of charge when the
engine operates. The control module assembly (CMA)
also incorporates a trickle charge circuit that maintains
battery state of charge during nonoperating periods.
Battery voltage should read approximately12.5 to 14.5
volts DC. A low battery voltage indicates the battery is
discharging.
3.1.5 HOURMETER
This indicates the time the engine-generator has operat-
ed, in hours and tenths of hours. Use the hourmeter
along with the periodic maintenance schedule for your
generator set.
3.1.6 AUTO/OFF/MANUAL SWITCH
See Section 3.2.
3.1.7 FAULT INDICATOR LAMP
This lamp goes ON when one or more of the following
engine faults occurs and when engine shuts down.
• Low oil pressure • High coolant temperature
• Low coolant level • Overcrank
• Overspeed
3.1.8 15-AMP FUSE
This fuse protects the control console’s DC control cir-
cuit against electrical overload. If the fuse has melted
open because of an overload, engine cranking and start-
up cannot occur. Replace the fuse with an identical AGC
15-amp replacement fuse.
3.1.9 7.5 AMP INLINE FUSE (NOT SHOWN)
This inline fuse is connected in the 15A line that runs
between the Auto/Off/Manual switch and position 10 of
the 76009A PCB. This fuse protects the start, fuel, field
boost, and transfer outputs from the PCB and will open
if there is excessive current draw on any one of these
outputs.
3.1.10 VOLTAGE-PHASE SELECTOR SWITCH
This switch permits selection between either line-to-line
or line-to-neutral voltage and amperage readings on the
console AC voltmeter and AC ammeter.
3.1.11 SET EXERCISE TIME SWITCH
This switch allows to program the generator to start and
exercise automatically. (See Section 3.6, page 14)
3.2 USING THE AUTO/OFF/MANUAL
SWITCH
3.2.1 “AUTO” POSITION
Selecting this switch position activates fully automatic
system operation. It also allows the unit to start and
exercise the engine every seven days with the setting of
the exercise timer.
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Section 3 — Operation
Guardian Liquid-cooled 40 kW Generator

3.2.2 “OFF” POSITION
This switch position shuts down the engine. This posi-
tion also prevents operation.
3.2.3 “MANUAL” POSITION
Set the switch to Manual to crank and start the engine.
Transfer to standby power will not automatically occur
unless there is a utility failure.
With the switch set to AUTO, the engine may
crank and start at any time without warning.
Such automatic starting normally occurs when
utility power source voltage drops below a preset
level or during the normal exercise cycle. To pre-
vent possible injury that might be caused by such
sudden starts, always set the switch to OFF and
remove the fuse before working on or around the
generator or transfer switch. Then, place a “Do
Not Operate” tag on the generator panel and on
the transfer switch.
3.3 AUTOMATIC TRANSFER OPERATION
To select automatic operation, do the following:
1. Make sure the transfer switch main contacts are set
to their “Utility” position, i.e., loads connected to the
utility power source.
2. Be sure that normal utility power source voltage is
available to transfer switch terminal lugs N1 and N2.
3. Set the generator’s Auto/Off/Manual switch to AUTO.
4. Set the generator’s main circuit breaker to its ON
(or closed) position.
With the preceding steps complete, the generator will
start automatically when utility source voltage drops
below a preset level. After the unit starts, loads are
transferred to the standby power source. Refer to
“Sequence of Automatic Operation.”
3.4 SEQUENCE OF AUTOMATIC
OPERATION
The generator’s control panel houses a control logic cir-
cuit board. This board constantly monitors utility
power source voltage. Should that voltage drop below a
preset level, circuit board action will signal the engine to
crank and start. After the engine starts, the circuit
board signals the transfer switch to activate and connect
load circuits to the standby power supply (load terminal
lugs T1/T2 connect to terminal lugs E1/E2).
Upon restoration of utility source voltage above a preset
level, generator circuit board action signals the transfer
switch to transfer loads back to that power supply. After
retransfer, the engine is signalled to shut down.
The actual sequence of operation is controlled by
sensors and timers on a control logic circuit board, as
follows:
A. Utility Voltage Dropout Sensor
• This sensor monitors utility source voltage.
• If utility source voltage drops below about 60 per-
cent of the nominal supply voltage, the sensor ener-
gizes a 15-second timer.
• Once the timer has expired, the engine will crank
and start.
B.Engine Warm-up Time Delay
• This mechanism lets the engine warm up for about
10 seconds before the load is transferred to a stand-
by source.
C.Standby Voltage Sensor
• This sensor monitors generator AC output voltage.
When the voltage has reached 50 percent of the
nominal rated voltage, transfer to standby can
occur.
D.Utility Voltage Pickup Sensor
• This sensor monitors utility power supply voltage.
When that voltage is restored above 80 percent of
the nominal source voltage, a retransfer time delay
starts timing.
E.Retransfer Time Delay
• This timer runs for about 15 seconds.
• At end of a 15-second delay, circuit board action de-
energizes transfer relay in the transfer switch.
• Retransfer to utility power source then occurs.
F. Engine Cool-down Timer
• When the load is transferred back to utility power
source, the engine cool-down timer starts timing.
• The timer will run for about one minute, and the
generator will then shut down.
3.5 ENGINE HEATER
This Generac standby generator comes equipped with a
block heater (Figure 3.2, page 14) that is similar to the
block heaters used in automotive applications. The
block heater must be connected to a customer supplied
120V AC circuit.
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Generac®Power Systems, Inc. 13
Section 3 — Operation
Guardian Liquid-cooled 40 kW Generator

Figure 3.2 – Engine Block Heater
Refer to applicable wiring diagram(s) and electrical
schematic(s) at the back of this manual for wiring con-
nections.
3.6 WEEKLY EXERCISE CYCLE
The generator will start and exercise once every seven
days. During this weekly exercise, the unit runs for
approximately 20 minutes and shuts down. Transfer of
loads to generator output does not occur during the
exercise unless power is lost during the exercise period.
To select the day of the week and time of day for exer-
cising, proceed as follows:
• Set the Auto/Off/Manual switch to OFF.
• Set generator’s main circuit breaker to its OFF (or
open) position.
• Locate the rocker switch on the control panel identi-
fied with the words “Set Exercise Time” (Figure 3.3).
• Push “Set Exercise Time” switch to the ON position
for 20 to 30 seconds and then release. The switch will
spring back into its original position when released.
• Wait 30 seconds before setting the Auto/Off/
Manual switch to the AUTO position.
NOTE:
The unit will exercise 20 minutes before it is set.
Example: Set – Noon; Exercise – 11:40 a.m.
If you switch the Auto/Off/Manual switch is
switched too soon, the engine may start. If
engine does start, it will shut down automatically
in about two (2) minutes.
• Set the generator’s main circuit breaker to its ON (or
closed) position.
• The generator is now programmed to start and exer-
cise every seven days thereafter, on the day and at the
time of day the switch was activated.
• Place a sign on the generator’s control panel and on
the transfer switch that indicates the day and time
the generator will be exercising.
NOTE:
If the battery terminals are disconnected or the con-
trol panel fuse is removed, the exercise timer needs
to be reset for automatic exercise operation.
Figure 3.3 – “Set Exercise” Switch on Control Panel
4.1 CHECKING THE ENGINE OIL LEVEL
For oil capacities, see “Specifications,” Section 1.7.2,
Page 6. For engine oil recommendations, see Section
4.2.1. To check the engine oil level, proceed as follows
(Figure 4.1):
1. Remove the dipstick and wipe it dry with a
clean cloth.
2. Install the dipstick cap; then, remove it again. The
oil level should be at the dipstick “Full” mark. If nec-
essary, add oil to the “Full” mark only. DO NOT FILL
ABOVE THE “FULL” MARK.
3. Install the dipstick.
Never operate the engine with the oil level below
the “Add” mark on the dipstick. Doing this could
damage the engine.
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Section 4 — Maintenance
Guardian Liquid-cooled 40 kW Generator
14 Generac®Power Systems, Inc.

Figure 4.1 – Oil Dipstick and Fill
4.2 CHANGING THE ENGINE OIL AND
FILTER
4.2.1 ENGINE OIL RECOMMENDATIONS
Use oil of API Service Class SG, SH or SJ. The
recommended oil grade for the engine is
SAE 15W-40.
NOTE:
The unit is supplied with “break-in” oil. See the
“Service Schedule,” Section 4.12 (Page 19), for
the first required oil change.
Any attempt to crank or start the engine before
it has been properly serviced with the recom-
mended oil may result in an engine failure.
4.2.2 OIL AND FILTER CHANGE PROCEDURE
To change the oil and filter, proceed as follows:
Refer to the “Service Schedule,” (Section 4.12, Page 19)
for engine oil and filter change frequencies.
Drain the oil while the engine is still warm from run-
ning. This means, warm up the engine, shut it down
and drain it immediately as follows:
1. Remove the oil drain hose from its retaining clip,
located on the generator base frame.
2. Loosen and remove the oil drain hose cap, located
on the base frame end of the hose. Drain the oil
completely into a suitable container.
3. When all of the oil has drained, install and tighten
the oil drain hose cap.
4. Turn the oil filter (Generac part number
0A37970001, Figure 4.2) counterclockwise and
remove it. Properly dispose of the old filter.
Figure 4.2 – Oil Filter
5. Apply a light coating of engine oil to the seal of
new oil filter. Install the filter and tighten by hand
only. DO NOT OVERTIGHTEN.
6. Remove the oil fill cap (Figure 4.1). Add the recom-
mended oil (see Section 4.2.1). DO NOT FILL
ABOVE THE DIPSTICK “FULL” MARK. Crankcase
oil capacity is 4.5 U.S. quarts (4.25 L).
After refilling the crankcase with oil, always
check the oil level on the dipstick. Never
operate the engine with the oil level below the
“Add” mark on the dipstick. Doing this could
damage the engine.
7. Start the engine and check for oil leaks.
8. Check the oil level after checking for leaks to
ensure that the oil is filled to the proper level.
4.3 CHANGING THE ENGINE AIR
CLEANER
To replace the engine air cleaner, (Generac part num-
ber 0A4637, simply remove the air cleaner cover and
replace the air filter making sure it is positioned
properly before reattaching the cover. (See Figure 4.3,
page 16).
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OIL FILTER
TO BASE
OIL DRAIN HOSE
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OIL FILL CAP
OIL DIPSTICK
Section 4 — Maintenance
Guardian Liquid-cooled 40 kW Generator
Generac®Power Systems, Inc. 15

16 Generac®Power Systems, Inc.
Figure 4.3 – Engine Air Cleaner
See the “Service Schedule,” Section 4.12, Page 19, for rec-
ommended air cleaner maintenance.
4.4 SPARK PLUGS
Reset the spark plug gap or replace the spark plugs as
necessary. See Section 4.12, Page 19.
1. Clean the area around the base of the spark plugs to
keep dirt and debris out of the engine. Clean the
plugs by scraping using a wire brush. Do not “blast”
the spark plugs to clean.
2. Remove the spark plugs and check the condition.
Replace the spark plugs if worn or if reuse is ques-
tionable. See the “Service Schedule,” Section 4.12,
Page 19, for recommended inspection.
3. Check the spark plug gap using a feeler gauge.
Adjust the gap to 0.045 inch (1.1 mm) by carefully
bending the ground electrode (Figure 4.4).
Figure 4.4 – Setting the Spark Plug Gap
4.5 BATTERY MAINTENANCE
The battery should be inspected per the “Service
Schedule,” Section 4.12, Page 19. The following proce-
dure should be followed for inspection:
1. Inspect the battery posts and cables for tightness
and corrosion. Tighten and clean as necessary.
2. Check the battery fluid level of unsealed batteries
and, if necessary, fill with DISTILLED WATER
ONLY. DO NOT USE TAP WATER IN BATTERIES.
3. Have the state of charge and condition checked.
This should be done with an automotive-type bat-
tery hydrometer or load test.
Standby generators installed with automatic
transfer switches will crank and start automatical-
ly when normal (utility) source voltage is removed
or is below an acceptable preset level. To prevent
such automatic start-up and possible injury to per-
sonnel, do not connect battery cables until the
normal source voltage at the transfer switch is
correct and the system is ready to be placed into
operation.
Storage batteries give off explosive hydrogen gas.
This gas can form an explosive mixture around
the battery for several hours after charging. The
slightest spark can ignite the gas and cause an
explosion. Such an explosion can shatter the bat-
tery and cause blindness or other injury. Any area
that houses a storage battery must be properly
ventilated. Do not allow smoking, open flame,
sparks or any spark producing tools or equipment
near the battery.
Battery electrolyte fluid is an extremely caustic
sulfuric acid solution that can cause severe burns.
Do not permit fluid to contact eyes, skin, clothing,
painted surfaces, etc. Wear protective goggles,
protective clothing and gloves when handling a
battery. If fluid is spilled, flush the affected area
immediately with clear water.
Do not dispose of the battery in a fire. The bat-
tery is capable of exploding.
Do not open or mutilate the battery. Released
electrolyte can be toxic and harmful to the skin
and eyes.
The battery represents a risk of high short circuit
current. When working on the battery, always
remove watches, rings or other metal objects, and
only use tools that have insulated handles.
4.5.1 BATTERY REPLACEMENT
Generac uses a Group 27F vented type battery that has
600 CCA @ 0º F. Generac’s part number is 058665.
NOTE:
The BCI number should be located directly on the
battery.
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DANGER
Air Cleaner
Section 4 — Maintenance
Guardian Liquid-cooled 40 kW Generator
0.045 inch (1.1 mm)

Generac®Power Systems, Inc. 17
4.6 COOLING SYSTEM
Air intake and outlet openings in the generator compart-
ment must be open and unobstructed for continued prop-
er operation. This includes such obstructions as high
grass, weeds, brush, leaves and snow.
Without sufficient cooling and ventilating air flow, the
engine/generator quickly overheats, which causes it to
shut down.
The exhaust system of this product gets extremely
hot and remains hot after shutdown. High grass,
weeds, brush, leaves, etc. must remain clear of the
exhaust. Such materials may ignite and burn from
the heat of the exhaust system.
4.7 OVERLOAD PROTECTION FOR
ENGINE DC ELECTRICAL SYSTEM
Engine cranking, start-up and running are controlled by
a solid-state engine controller circuit board. Battery
voltage is delivered to that circuit board via a 15-amp
fuse. These overcurrent protection devices will open if
the circuit is overloaded.
If a circuit breaker opens or a fuse element melts,
you should find the cause of the overload before
resetting the circuit breaker or replacing the fuse.
4.8 DC FUSE
The generator panel’s 15-amp AGC fuse (Figure 4.4) pro-
tects the DC control circuit against overload. The fuse is
wired in series with the battery output lead to the panel.
If the fuse element has melted open, cranking or starting
the engine cannot occur. Replace the fuse using only an
identical 15-amp AGC replacement.
Figure 4.4 – Location of 15-amp Fuse
4.9 ENGINE COOLANT
Check the coolant level in the coolant recovery bottle.
• Add the recommended coolant mixture as necessary.
See Section 1.10 on Page 7.
• Periodically remove the radiator pressure cap to make
sure the coolant recovery system is functioning
properly. Coolant should be at the bottom of the radia-
tor filler neck. If the coolant level is low, inspect the
gasket in the radiator pressure cap. Replace the cap, if
necessary. To have the pressure cap tested, contact a
Generac/Guardian Authorized Dealer. Inspect the cool-
ing system and coolant recovery system for leaks.
4.10 MISCELLANEOUS MAINTENANCE
4.10.1 CLEANING THE GENERATOR
Keep the generator as clean and as dry as possible. Dirt
and moisture that accumulate on internal generator
windings have an adverse effect on insulation resist-
ance.
Periodically, clean the generator’s exterior surfaces. A
soft brush may be used to loosen caked on dirt. Use a
vacuum system or dry, low pressure air to remove any
accumulations of dirt. The generator is housed inside
an all-weather enclosure; clean the enclosure with a
soft, damp cloth or sponge and water.
Once each year, have the generator cleaned and inspect-
ed by a Generac/Guardian Authorized Dealer. Service
technicians will use dry, low pressure air to clean inter-
nal windings. Parts inside the control console should be
cleaned and inspected at this time as well.
Finally, have the insulation resistance of stator and
rotor windings checked. If insulation resistances are
excessively low, the generator may require drying.
4.10.2 RODENT PROTECTION
The intrusion of rodents into the generator set can
cause a wide range of problems, from failure of the unit
to start, to personal injury and, in extreme circum-
stances, short circuit or fire. Although the unit was
designed to limit this problem, further precautions can
be taken by the owner to help minimize both the chance
of rodent entry and the extent of any damage. The fol-
lowing inspection should be performed.
1. The base frame of the unit contains an optional fuel
inlet location and four lifting holes that are capped
at the factory. These caps are sometimes removed
for transportation during installation but always
should be replaced afterwards. Check that they are
secured in place. The same applies for any access
ports in the roof of the enclosure. If any of these
caps are missing, contact a Generac/Guardian
Authorized Dealer.
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Section 4 — Maintenance
Guardian Liquid-cooled 40 kW Generator

18 Generac®Power Systems, Inc.
2. Inside the generator set, the chance of rodent entry
into the control panel is greatly reduced by the
inclusion of adjustable wire connectors. Check that
the wire connector screws are tight, thus closing off
any gap between the access holes and the wires.
4.11 OUT OF SERVICE PROCEDURE
4.11.1 REMOVAL FROM SERVICE
If the generator cannot exercise every seven days, and it
is to be out of service longer than 90 days, prepare the
generator for storage as follows:
1. Start the engine and let it warm up.
2. Close the fuel shutoff valve in the fuel supply line
and allow the unit to shut down.
3. Once the unit has shut down, it will signal a fault on
the control panel.
4. Set the Auto/Off/Manual switch to OFF and turn off
the utility power to the transfer switch.
5. While the engine is still warm from running, drain
the oil completely. Refill the crankcase with SAE
15W-40 oil having API Service Class SG, SH or SJ.
6. Attach a tag to the engine indicating the viscosity
and classification of the oil in the crankcase.
7. Remove the spark plug(s) and spray fogging agent
into the spark plug(s) threaded openings. Reinstall
and tighten the spark plug(s).
8. Remove the battery and store it in a cool, dry room
on a wooden board. Never store the battery on any
concrete or earthen floor.
9. Clean and wipe the entire generator.
4.11.2 RETURN TO SERVICE
To return the unit to service after storage, proceed
as follows:
1. Verify that utility power is turned off to the transfer
switch and that the Auto/Off/Manual switch is set to
OFF.
2. Check the tag on the engine for oil viscosity and
classification. Verify that the correct recommended
oil is used in engine. See Section 4.2.1 (Page 14). If
necessary, drain and refill with the proper oil.
3. Check the battery. Fill all cells to the proper level
with distilled water. DO NOT USE TAP WATER IN
THE BATTERY. Remove the battery before charging.
Recharge the battery to 100 percent state of charge,
or, if defective, replace the battery with a 12-volt DC
Group 27F battery rated for 90 amp hours (part #
058665).
4. Clean and wipe the entire generator.
5. Reconnect the battery. Observe battery polarity.
Damage may occur if the battery is connected incor-
rectly.
6. Open the fuel shutoff valve.
7. Start the unit by moving the Auto/Off/Manual switch
to MANUAL. Allow the unit to warm up thoroughly.
8. Stop the unit and set the Auto/Off/Manual switch to
AUTO.
9. Turn on the utility power to the transfer switch.
10. The generator is now ready for service.
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Section 4 — Maintenance
Guardian Liquid-cooled 40 kW Generator