Connecting a generator
Direct Connection: A directly connected generator can 'backfeed' onto the power lines connected to your home. Utility transformers can then step-up or magnify this backfeed to thousands of volts—and that can be a hazard to a utility lineworker making outage repairs.
To power your household circuits directly, you must install a transfer switch. Whether automatic or manual, a transfer switch makes sure your household wiring, or selected circuits to be supplied by the generator, can't be connected to the utility grid and to your generator at the same time. That prevents backfeed -- and the risk of having your generator damaged or destroyed if utility power is restored while the generator is connected to your wiring. A licensed electrician will install the switch for you.
Portable Connection: Portable generators aren't intended to be connected directly to your household wiring, but to the items you wish to power. Use properly sized, outdoor-rated cords to power chosen end uses such as a stove, refrigerator, furnace, water pump, or lamps. If a portable unit is to be hooked to household circuits rather than to appliances themselves, it needs a transfer switch and a dry, solid mounting in a properly vented area, just as a permanent unit does. Portable generators need to be grounded, just like other major electrical devices. See your owner's manual for details.