Home Generator Selection, Installation and Repair

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About the author

Paul Dempsey is a master mechanic and a former magazine editor. He is the author of some 30 technical books with subjects ranging from bicycles to heavyduty diesel engines. He is the owner of a shop, located in a rural area south of Veracruz, Mexico, that aspires to be a universal repair station. Almost anything that comes in the door—generators, tractors, marine engines, garden equipment—can be fixed. The shop’s collection of antique machine tools enables many parts unobtainable in Mexico to be fabricated.

Contents

Preface

1 • Selecting the right generator

Outages

What’s available

Power output

Power quality

Voltage

Frequency

Distortion

Engines or prime movers

Fuel options

Other features worth having

Instrumentation

Circuit breakers

Ground-fault circuit interrupters

Automatic idle control

Noise

Sizing

2 • Powering up

Location

Hookup

Power cords

Power inlet box

Transfer switches

Transfer switches and neutral grounds

Electrical safety

Grounding rods

Fuels

Gasoline

Propane

Natural gas

Diesel

Planning ahead

3 • Generator repairs

Conventional generators

Brushed generators

Brushless generators

Power quality

Tools

Measurements

Output tests

Resistance tests

Ohmmeter tests

Megaohmmeter tests

Rotor excitation test

Inverter generators

Operation

Troubleshooting

4 • Engine electrical

Engine management controls

Power sources

Fuel cutoff valves

Idle control

Automatic choke

Oil-pressure sensor

Oil-level sensor

Solid-state ignition

Ignition myths

Starter motors

5 • Emergency repairs

Tools and supplies

No power

No power from any receptacle

No power from one receptacle

Genset slows under load

Storage batteries

Gasoline engine malfunctions

Preliminaries

No start

Loss of power as engine warms

Sudden shutdowns

Insufficient power

Weak compression

Diesel engine malfunctions

No or slow starting

Runaway

6 • Fuel systems

Basic carburetor theory

Tools and supplies

Parts and materials

Removal and installation

Cleaning

Float carburetor service

Needle and seat

Float adjustments

Jets

Primer

Diaphragm carburetor service

Diaphragm carburetor operation

Plumbing

Troubleshooting

Pressure test

Mixture-adjustment screws

Fuel pumps

Metering

Idle circuits

Check valves

Final pressure check

Mixture adjustments: all carburetors

Fuel injection

Diesel

Wet stacking

Safety

Tools

Fuel system checks

Injectors

High-pressure pump

Timing

7 • Major engine repairs

Some basics

What’s needed

Torque limits

Evaluation

Excessive compression

No or barely perceptible compression

Compression test

Leak-down test

Leak-down test—four-cycle engine

Leak-down test—two-cycle engine

Blowby gauge

Cylinder head casting

Valves

Valve guides

Valve springs

Pushrods

Pistons

Rings

Installation

Piston installation

Integral bores

Detachable cylinders

Connecting rods

Construction

Orientation

Bearings

Micrometers

Plastigage

Failure analysis

Rod assembly

Cylinders

Glaze breaking

Inspection

Boring

Sleeving

Flywheel

Crankcase

Crankshafts

Antifriction main bearings

Camshafts

Balance shafts

Oil seals

Oil circuits

Rewind starters

Starter troubleshooting

Preload release and restoration

Brake

Dogs

Recoil springs

A final word

A • Generator websites

B• National Electrical Manufacturers Association (NEMA) plug and receptacle configurations

Index

Preface

Millions of Americans depend on portable generators to provide power during the blackouts that have become increasingly frequent. According to the Eaton Corporation, the number of outages affecting 50,000 people or more doubled between 2010 and 2011. A half-million people lose grid power every day in this country.

There are various reasons why the North American grid, once the envy of the world, can no longer keep pace with demand. Some critics blame poor maintenance, others see privatization—80 percent of the grid is privately owned—as the culprit, and still others point to the high level of integration that can escalate local failures into regional catastrophes. An example of the latter occurred in August 2003. A high-voltage transmission line sagged, touched a wet tree branch, and shorted to ground. This produced a cascade of exploded transformers and burned-out wiring that shut off power to 50 million people in eight states and parts of southern Canada. The outage cost several billion dollars and the lives of 11 people.

A portable generator—one with good build quality, sized for the loads, and properly maintained—will keep the lights on. But generating your own electricity is not a simple, plug in and play proposition. This book describes:

• How to purchase the right generator for your needs. The first requirement is to make sense of the esoteric engineering terms used in the sales literature. Next, one must determine how much electricity is needed during a blackout. Do you want to power your whole house? If not, which loads are critical? The more power required, the greater the cost.

Most people specify a gasoline-powered generator, but diesel, propane, and natural gas have advantages for certain applications. The best diesel generators are industrial products that should give decades of reliable service.

Then there is the question of quality. Many generators are poorly constructed devices without much of anything by way of factory support. The book describes ways to evaluate build quality before purchase.

Certain features, such as large, easy-rolling, pneumatic tires; steel—not plastic—fuel tanks; basic instrumentation; and ground fault protection on output circuits, are important and worth paying extra for.

• How to connect the generator. There are various ways, each with advantages and disadvantages, to safely connect auxiliary power to your home or office. An improperly connected generator can impose serious risks, both to yourself and to linemen working to restore grid power. You will need to purchase an appropriate power cord and make provision for storing fuel, and you should have some spare parts, such as filters and spark plugs, on hand.

• How to troubleshoot and repair generator malfunctions. For the most part, portable generators are simple machines, quite within the capabilities of do-it-yourself mechanics to repair. The book goes into detail on how generators work and how to recognize and test various circuit components. It also includes a comprehensive list of parts suppliers.

• How to troubleshoot and repair generator engines. The engines that power generators spend much of the time idle, waiting for a blackout. When the lights go down, they work hard at something like 80 or 90 percent of maximum power. The combination of long periods of storage followed by near full-throttle operation is a recipe for trouble. Unless you buy a state-of-the-art industrial generator, you will sooner or later be working on the engine.

This section of the book describes how to identify the causes of gasoline and diesel engine malfunctions and provides detailed repair information. The material applies to all small engines, not merely to those that power generators.

The book is written by a DIY mechanic for other DIY mechanics who do not have access to factory tools or training. I have tried to illustrate all critical parts, so that nonprofessionals can recognize what they’re dealing with. In so far as space permits, wiring diagrams are provided. Special tools are described in enough detail to enable readers to fabricate their own.

Overall, the emphasis is on safety. Portable generators present hazards, both when using them and, especially, during repair operations, some of which must be accomplished while the generator is running.

Paul Dempsey

1

Selecting the right generator

In September 1882, a 100-kW generator came on line to provide electric power to a few square blocks in lower Manhattan. Factories, hotels, and a few ships previously had been electrified by their owners. But Thomas Edison’s Pearl Street Station was the first to generate power for anyone within range who was willing to pay for it.

Pearl Street turned a profit within two years, and other entrepreneurs set up local generating stations, most of which used alternating current (AC) rather than the 110-V direct current (DC) favored by the inventor. Alternating current is variable-voltage power that is easy to step up for transmission and to step down for safe residential use By the 1930s, the local generating stations were combined into regional distribution networks that would coalesce a few decades later into the three main grids that serve the continental United States and parts of Canada and northern Mexico (Fig. 1-1).

FIG. 1-1 The national grid reflects past population density. FEMA

Power for the grid comes from more than 12,000 generating units:

• Base-load units operate continuously to meet normal demand

• Peaking generators are dispatched during periods of high demand, such as late-afternoon summer days.

• Intermediate, or cycling, units bridge the gap between normal and peak demand.

Because coal is cheap, most base-load generators are coal-fired (Fig. 1-2). Peaking generators, consisting for the most part of oil-fueled turbines, are the most expensive to run. In the past, natural gas was pretty well confined to intermediate units, but recent declines in natural gas prices make the fuel practical for base-load generation. Although wind and solar generators have the lowest operating costs, utilities have difficulty integrating these variable-output devices into their systems. The wind blows as it will, and the sun goes down every night.

FIG. 1-2 Coal remains the dominant generator fuel, used in nearly all baseline plants. EPA

Outages

Unfortunately, the North American grid, considered by many to be the world’s largest and most complex machine, has not aged well. One indication is the number of power interruptions. According to the Eaton Corporation, the frequency of blackouts affecting more than 50,000 people nearly doubled between 2010 and 2011. And repairs are slow. Three Carnegie Mellon professors found that power outages last seven times longer in the United States than in the Netherlands and four times longer than in France. The study was done in 2006; since then, response time has slowed. The American Society of Civil Engineers gives the grid a grade of D+. Should you need any more convincing, the World Economic Forum puts the American grid in thirtieth place, behind the distribution systems of 29 other countries, some of them barely industrialized.

Most of us are all too familiar with blackouts. For those who aren’t, it’s worth noting that when the power goes down, so does nearly everything else. Urban residents experience a loss of water pressure, and rural residents who depend on wells do without water. If a blackout occurs in summer, air conditioners and fans go out, which means that office buildings and most modern homes become uninhabitable. Heat stroke is a real danger when the humidity is high and ambient temperatures are above body heat. In winter, central heating systems no longer function. People take refuge in their automobiles, running the heaters so long as they have gasoline.

Nor can one easily escape an area-wide blackout. Freeways clog, traffic signals no longer function, and gas stations cannot pump fuel from their underground tanks. Local radio and television stations go off the air, and cell phones may not work. A blackout of any length represents a return to the past, but without the amenities, the ways of coping, that people in earlier centuries enjoyed.

Most short-term outages come about because of routine weather events—high summer temperatures result in greater demands for electricity than overworked transmission systems can deliver or a cold snap ices over and breaks power lines. Systems also go down during the first rain after a long dry spell. The accumulated dust becomes conductive, and transformers short out, often explosively.

Intrusions are another source of brief blackouts. Birds get themselves across power lines, a truck knocks down a transmission tower, or a backhoe operator cuts an underground line. Intrusions are impossible to prevent, but happen frequently enough to be predictable. For example, the Edison Electric Institute blames foraging animals for 11 percent of U.S. blackouts. Most of us cope with these short-term inconveniences.

The triggers for long-term catastrophic outages usually take the form of hurricanes,