Electricity Generators

To determine the size of the generator needed, total the rated watts of the appliances and fixtures you’ll want to operate during an outage. Some loads are easy to determine — a 100-watt light bulb, for example, uses 100 watts. Ten 100 bulbs would require 1,000 watts, or 1 kilowatt (KW). The power requirements for appliances are often provided in the operating manual. These specifications are also stamped on the “face plate” along with serial and model numbers.

While the power needs of individual appliances vary, those that produce heat or use large motors tend to require higher wattages.

An average 14 cubic-foot refrigerator with automatic defrosting, for example, requires about 615 watts while an electric range at 12,220 watts needs nearly 20 times as much power. Electric space heaters and water pumps are usually rated at 1,000 to 1,800 watts (1-1.8 KW) and electric water heaters require 2,500 to 4,500 watts (2.5-4.5 KW).
As you can see, a household’s power requirements can quickly add up.

Power needs for motors, such as those powering well pumps or furnace fans, are more difficult to determine. Electric motors require more current when starting than they do in continuous operation-as much as three to six times more.

Motors are rated by horsepower (hp). A one-horsepower motor requires about one kilowatt to run and a surge of five kilowatts to get started. An electric motor rated for two-horsepower needs twice as much power. So while a motor-powered appliance may run with only one kilowatt, the generator must be able to provide five kilowatts to get it started. Again, those ratings appear on the motor’s face plates. Without sufficient starting power, motors may overheat, burn out or trip the generator’s circuit breaker.

Generators come in two basic configurations — manual or automatic start. Manual start systems enable users to get by with smaller generators, provided that all equipment is not restarted at the same time.

After a power failure, disconnect all equipment. Once the standby generator is running, restart motors one at a time beginning with the largest motor. This procedure reduces needed power. Since the extra start-up power is not necessary while equipment is running, power for other equipment-such as lamps and appliances-is available.

Automatic standby systems, however, must be capable of starting and running all equipment connected to them. They must be large enough to provide both the start-up and continuous power needed by all motors, as well as that needed by the lights and appliances in the home, business or farm.

To cut costs when planning an emergency power supply for a home or business, consider providing sufficient capacity for only essential appliances, disconnecting the “frills” until normal service is restored.

More important than sizing is correct installation. Auxiliary power sources must be completely isolated from WECo lines attached to your meter to avoid “backfeed” into WECo’s system. During an outage, line workers trying to restore power-or anyone who contacts a downed line-could be seriously injured or killed by backfeed from an improperly installed generator.

A special switch is used to transfer a building’s wiring from normal to a standby power source. The switch- called a double-throw device- is designed to prevent a generator’s feedback from passing through the WECo’s lines and transformers. The switch makes it impossible to connect the main power source to the generator. Its use is required by the National Electric Code when connecting an auxiliary power source to an existing system.

Remember, the switch and its wiring will carry all the load for the building it serves when connected to WECo lines during normal operation. These switches, like the generators they connect, are available in several configurations and power ratings. Choose one matched to your service connection- 200 amp, 400 amp, three-phase, etc.- not one matched to the generator output.

In most areas, local codes and co-op policies require that auxiliary power connections be inspected and approved by a recognized electrical inspection agency before they can be used.

If you are considering installing an emergency back-up generator, contact your local co-op as well as generator equipment dealers. Together they can help you select a system that will safely provide temporary power when needed without creating additional problems or hazards.