![]() = 40 amps, the maximum rating for the backfed PV breaker. ![]() ![]() Take 120% of the busbar rating minus the main breaker rating equals the maximum rating of backfed PV breaker.įor the 200-amp busbar with a 200-amp main breaker: Also, the 120 percent rule would apply where the largest backfed PV breaker would be 20 amps for a 100-amp busbar, 25 amps for a 125-amp busbar and 40 amps for a 200-amp busbar.Īn example of the math leading to these restrictions is: In this situation, Section 705.12(B)(2)(3)(b) would apply and the backfed PV breaker must be at the end of the busbar most distant from the main breaker connection. Load breakers and the PV breaker, if any, are connected to that busbar. In a typical meter-main combo panel, the main breaker has the same rating as the busbar in that panel. Option 2 shows a feeder tap for the PV connections. Diagram of meter-main combination service entrance panel. Since this breaker and the PV connection are on the load side of the service disconnect/main breaker, the PV connection becomes a load-side connection and the requirements of Section 705.12(B) apply. If the meter-main combo has load breaker positions in the enclosure, then if one of these is not being used, a backfed PV breaker may be installed (see figure 1, option 1). In some areas, the utility considers the circuit between the meter socket and the service disconnect/main breaker to be utility property and does not allow connections under any circumstances. However, a field inspection by a nationally recognized testing laboratory (NRTL) - the listing NRTL or other NRTL authorized by OSHA to make such inspections - may be required by either the manufacturer or the authority having jurisdiction (AHJ). Occasionally, the manufacturer of the meter-main combo may provide instructions and hardware to make such a connection. The utility has locked the metering section. Four 2-pole breaker positions are available for loads as are main lugs for feed through. Meter-main combination service entrance panel. Doing so would violate the listing on the equipment, which in turn violates Section 110.3(B), which requires that all listed equipment be used in accordance with the instructions furnished with that listed equipment and any restrictions associated with the listing. While there may be exposed, readily accessible busbars or conductors between the meter socket and the main breaker/service disconnect, it is not legal to tap these circuits to make a supply side PV connection. These panels have a meter socket in the same enclosure as the main breaker, and some may also have positions for a few load breakers. The meter-main combination panel is quite common in many sections of the country (photo 1). Utility Connections at Existing Service Entrance Panels Meter-Main Combo Panel This article provides some insight into the most frequently received questions and opens the discussion on items that may lead to clarifications and changes in the Code. ![]() Over the years, some of these questions come up repeatedly, while others are unique. Nearly every week, I get calls and e-mails from inspectors, plan reviewers, photovoltaic (PV) professionals, engineers, and electricians asking about areas of PV system installation that are not clearly addressed in the National Electrical Code ( NEC).
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