Grounding a PV System

[Leo1]

When installing a supply-side disconnect to feed a new PV system the NEC states a main bonding jumper must be placed between the grounded conductor and the equipment grounding conductors at the first disconnectin means of the supply. However on a PV system the first disconnecting means of the supply is usually near the array of multiple modules and inverters which are often hunderds of feet from the main utility and the new supply-side disconnect. At which disconnect on the new PV system is the grounded conductor to be tied to the equipment grounding conductors - at the new supply-side disconnect or the source of the PV power? Likewise where should the grounding electrodes be placed at the new suppl-side disconnect or the source of the PV power.

 

[jaggedben]

For the purposes of Article 250, the utility is still the source of supply, and the main bonding jumper applies to the AC system. The new conductors created by a line side tap are treated just like any other service or service entrance.

Grounding of the PV system is a totally separate question. Nowadays it is extremely unusual for an installer to have to install anything that grounds the PV system. That is almost always handled internally by the inverter. (Most exceptions would be in small off-grid systems, and even then it should usually be handled by the equipment.) Connecting any PV system conductor to ground at a PV system disconnect would compromise the ground-fault protection in the inverter and could be highly dangerous. Also note that PV systems are not required to be grounded if they comply with 690.35.

To go back to the AC side... I have witnessed one major dispute as to whether a neutral service conductor is required for a line-side tap where the inverter does not require an neutral to operate. In that case an electrical engineer prevailed in convincing an AHJ that it wasn't required, and that a single grounding (green) conductor served all the grounding and fault path needs. OTOH, Marvin Hamon has written over at Solar Pro magazine that you bring a neutral to the service disconnect and bond it to ground as with any grounded service, even if the neutral goes no farther than that.

 

[Leo1]

For the purposes of Article 250, the utility is still the source of supply, and the main bonding jumper applies to the AC system. The new conductors created by a line side tap are treated just like any other service or service entrance.

Grounding of the PV system is a totally separate question. Nowadays it is extremely unusual for an installer to have to install anything that grounds the PV system. That is almost always handled internally by the inverter. (Most exceptions would be in small off-grid systems, and even then it should usually be handled by the equipment.) Connecting any PV system conductor to ground at a PV system disconnect would compromise the ground-fault protection in the inverter and could be highly dangerous. Also note that PV systems are not required to be grounded if they comply with 690.35.

To go back to the AC side... I have witnessed one major dispute as to whether a neutral service conductor is required for a line-side tap where the inverter does not require an neutral to operate. In that case an electrical engineer prevailed in convincing an AHJ that it wasn't required, and that a single grounding (green) conductor served all the grounding and fault path needs. OTOH, Marvin Hamon has written over at Solar Pro magazine that you bring a neutral to the service disconnect and bond it to ground as with any grounded service, even if the neutral goes no farther than that.

Thank you.