![]() ![]() Here is an example of a de-rated electrical panel to handle a larger solar system: Now, the main breaker can be changed to a smaller size (e.g. Therefore, 40A is the maximum solar output for a 200A panel with a 200A main OCPD, unless de-rated.The 120% Rule back-feed limit for solar is calculated as: The circuit breaker is technically called an Over Current Protection Device, or OCPD.įor example, a 200 Amp electrical panel is rated with a 200A busbar, and commonly has a 200A Main OCPD breaker. The electrical panel rating Amps (A), or Busbar rating, is the manufacturer rating typically found on a label. Known as the 120% rule, the solar circuit breaker can be no more than 20% of the main electrical panel rating. Both rules must be satisfied to meet Code when using a load-side connection. When using a load-side connection, two NEC rules govern the size allowed based on the electrical panel size and the solar output size. Some inverters include the disconnect or an external disconnect can be added cheaply. An adequately sized PV service disconnect box must be used before making the connection. Then the wires from the PV solar system will be connected to this new solar breaker. The circuit breaker will be dual-pole or double-space, and it will be located in a position farthest from the main breaker. A new circuit breaker(s) will be added to the electrical panel. In simple terms, a Load Side connection is made AFTER the main breaker in the electrical panel this is the most common method of connecting. The alternative is a "LINE OR SUPPLY-SIDE" connection made BEFORE the main breaker. The most common is a "LOAD SIDE" connection, made AFTER the main breaker. ![]() There are two basic approaches to connecting a grid-tied solar panel system, as shown in the wiring diagrams below. Always refer to the NEC code in effect or consult a licensed electrician for safety and accuracy. The utility connection for a PV solar system is governed by the National Electrical Code (NEC) Article 690.64. The purpose of this article is to give you a basic understanding of the concepts and rules for connecting a solar panel system to the utility grid and the household electrical box or meter. Here are design tips for methods of PV system utility interconnection.
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