Wiring A Home Standby Generator
January 8, 2006
Q: Does Article 230 apply to the conductors and overcurrent protection from a standby generator located outdoors about 20 feet from the building it serves?
A:No, Article 230 applies to services, and the definition of a service, which appears in Article 100, reads: “Service. The conductors and equipment for delivering electric energy from the serving utility to the wiring system of the premises served.” The key words in this definition are “serving utility;” therefore, Article 230 does not apply.
Article 445 covers generators and references Article 695, 700, 701, 702 and 705, which must be complied with depending on the generator’s use. Alternating current machines must be protected from overloads by inherent design, fuses, circuit breakers or other acceptable overcurrent protection.
Supply-conductor ampacity from the generator to the overcurrent protection cannot be less than 115 percent of the nameplate current rating of the generator. These requirements appear in 445.12(A) and 445.13.
If the standby generator supplies a fire pump, additional requirements for the generator set are found in Article 695. A generator used to supply emergency power must comply with the rules in Article 700, especially 700.12(B).
Requirements for a legally required standby system are similar in some respects to those in Article 700 and are in Article 701. If the generator is connected to optional standby loads, Article 702 applies. Where the generator operates in parallel with the utility system, Article 705,Interconnected Electric Power Production Sources applies. Each Article has different requirements but they all prohibit inadvertent parallel operation of the generator with the utility system.
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