This article, written by the American Ground Water Trust was originally published in THE AMERICAN WELL OWNER, 1999, Number 3


When the power goes out during a storm or other emergency, it is convenient to have a generator to get the "lights and the water back on." Generators have wattage ratings that help the operator determine the number and type of appliances and motors that may be operated at one time. One horsepower (Hp) is equivalent to 746 watts. Most residential water pumps are rated between one-half and two Hp for normal operating conditions. All things being equal, water pumps in deeper wells require more horsepower to operate efficiently than pumps in shallow wells.

Your water pump may require 15 to 50 percent more power (watts) to start up than the normal operating Hp rating of the pump in order to accommodate the starting torque of the motor. It is important to have enough generator power in reserve to cover peak electricity demands as appliances turn on and off. You may notice the lights dim or the generator strain temporarily when the water pump starts up and a surge of extra current is required. Limit the number of electrical appliances in operation at any one time to avoid over taxing the generator and/or running equipment at below recommended-voltage levels.

To avoid electrical hazards, always consult the generator-operating manual and hire a qualified electrician when connecting a generator into a building's electrical system. National building code requires that all generators tied into a public utility power grid (commercial power lines) use a "double-pull double-throw" (transfer isolation) switch to prevent the risk of backfeeding current from the generator to the main grid. The isolation switch automatically disconnects the home or business electrical wiring from the main grid and ties it into the generator. Backfeed of any current to the main grid can cause serious injury or electrocute line maintenance personnel working on the main grid powerlines. Also, generator and building electrical system damage can occur when normal operating power returns if the generator is used without an isolation switch.

Other safety concerns include: ß Ground the generator during operation with a wire of sufficient current capacity (Copper wire

diameter: 0.12 millimeters [0.005 inches] per ampere). ß Do not connect the generator to a commercial outlet. ß Do not connect the generator to another generator. ß Exhaust fumes from the generator are poisonous and may cause unconsciousness or death. Always

operate the generator in a well-ventilated area where the exhaust from the gas engine will not

accumulate. Do not operate the generator inside a building. ß Always turn off the generator when refueling. Avoid spilling fuel on the muffler or other hot engine

parts. ß Operate the generator at least one meter (3 feet) from buildings, other equipment and not under a

tight-fitting dust or weather cover to avoid overheating the generator engine. ß Keep children away from operating or hot generators. ß To avoid electrical shock, do not operate the generator in direct rain or snow. Do not touch the

machine with wet hands.

[© American Ground Water Trust. This article may be reprinted for non-commercial educational purposes provided it is used in its entirety and that reference is made to its source as an article in THE AMERICAN WELL OWNER, 1999, Number 3]