| Generator Safety |
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Page 3 of 4 “Back Feeding” - a dangerous conditionImproperly connecting a portable generator to electric wiring can produce “back feed” - a dangerous current that can electrocute or critically injure you or others. Back feed into power lines from a generator could create “hot” power lines during an outage. Linemen who expect the line to be de-energized could be injured. One good way to avoid back feeding is to install a double-pole, double-throw transfer-switch gear. A qualified electrical contractor can install this transfer switch so that a dangerous back feed can be prevented. “In accordance with the National Electric Code, paragraph 700-6; Transfer equipment shall be designed and installed to prevent the inadvertent interconnection of normal and emergency sources of supply in any operation of the transfer equipment. Automatic transfer switches shall be electrically operated and mechanically held.” The transfer switch must be a break-before-make switch which will “break” the electrical connection with commercial power lines before it “makes” the connection between your generator and wiring. The switch also will prevent utility power from damaging the generator when regular service is restored. Make sure the transfer switch is rated at the same or greater than the main over current protection. An electrical diagram of a typical installation using a transfer switch appears in Figure 1. You should always consult a licensed and experienced electrician and follow all local building and electrical codes. Since transfer switches can be expensive, another way to install a generator is to have a sub-panel with main breakers and power from the main power or generator. Main panel breaker and generator breaker in sub-panel would have handles interlocked to prevent both being opened and close at the same time. This prevents back feed to commercial power when generator is in use. See Figure 2. |