how to use a generator during a power outage

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A portable generator is a convenient way to safely generate your own power when the grid goes down due to either natural or man-made causes. Whether you’re new to using a generator or well experienced, there are a few things you need to know to operate it safely.

“The single biggest thing you can do to run a generator safely is plan how to use your generator before you need it,” says Kevin Cole, associate engineer for generator manufacturer Generac. Plan what you want to power and how you will use the generator to power those loads.

Electrical Safety

1. Size Matters Size the generator correctly so that it meets the electrical loads you intend to power with some excess capacity built in. We’ve written on this topic as have many others, so there’s no shortage of good information out there. If you undersize the generator, you produce essentially the same condition as a utility “brown out” condition with insufficient voltage. This can damage something as big as a well pump or as small as a computer.


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2. Use a Transfer Switch The safest way to use a portable generator for home power backup is to use it in conjunction with a manual transfer switch­–a robust piece of electrical gear. The generator connects to the transfer switch with a thick, heavy-duty cable called a genset cord which is plugged into an outlet receptacle installed on the outside of the house (that receptacle is officially known as a power inlet box). A cable on the inside of the house runs from the outlet to the transfer switch. Electricity from the generator runs through the genset cord, to the receptacle, through interior cable, to the transfer switch and its circuit breakers to the various circuits you need to power–safely.ADVERTISEMENT – CONTINUE READING BELOW

The transfer switch has three purposes:

  • It isolates the circuits in the house that you want to power; all other circuits are left without access to power, helping to prevent overloading.
  • The transfer switch electrically isolates the generator and the house from the grid. This prevents generated power from backfeeding electricity onto the grid and sparking a fire, or injuring utility personnel who have come to do repair work and restore power.
  • The switch prevents utility-supplied power from powering the house while the generator is running, causing an electrical fire and likely catching the generator on fire as well.

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3. Use a GFCI Transfer Switch on a GFCI Generator The National Electrical Code (NEC) requires GFCI (ground fault circuit interrupter) outlets on dual-voltage generators (those that produce 120 and 240 volts). Generators that are equipped with GFCI outlet receptacles require a transfer switch designed for them. This switch may be called a three-pole switch or simply a GFCI-compatible switch, and it is also required by the NEC. When you throw this switch, you not only separate the generator-supplied circuits from the two 120-volt circuits supplied by the utility, you also disconnect a third leg of the utility-supplied circuit, called the neutral. If you use a standard 2-pole transfer switch on a GFCI-equipped generator (which does not disconnect the neutral), the GFCI outlets will trip off. The use of this switch is an electrical code violation, and by defeating the GFCI receptacles, you’ve limited the generator’s capability­. This is ironic, since you’ve paid extra money to have that GFCI protection. You can use a 3-pole switch or a 2-pole transfer switch on all other types of (non-GFCI) generators.

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4. Use Heavy-Duty Cords, Correctly Suppose you don’t have the money yet to have a transfer switch installed. You can safely operate appliances plugged directly into the generator. You can power your refrigerator, power tools, and computers (for example) by running long extension cords to the generator. These cords should be heavy-duty and of a thick enough wire gauge to handle the current flowing through them; the cord’s packaging will tell you what electrical load it’s rated to supply. Next, the cords should be rated for exterior use. Finally, you want to run cords in a manner that they won’t be damaged, kinked, or coiled up—particularly while powering a high-wattage device like a heater. Coiled extension cords can get so hot, they can melt.

There is a correct sequence to power a load through an extension cord. Start the generator, and plug the cords into it. Then go inside and plug the loads into the extension cord. Do the opposite when it’s time to disconnect the loads. Unplug the loads from the generator, then go outside and unplug the cords, and turn the generator off.

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5. Understand When and How to Use a Ground Rod Don’t connect the generator to a ground rod when you plug loads directly into the generator by extension cords. To restate that: If you plug a heavy-duty extension cord into the generator and connect that to an appliance, power tool, or device, skip the ground rod

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