System Specifications
System Ground Requirements
This product is intended to be installed as part of a permanently grounded electrical system per the National Electric Code ANSI/NFPA 70. A copper ground rod must be installed within three feet of the PV100S enclosures and connected to the unit as described in “System Grounding” on page 3–12. The single-point ground for the system is to be made at the AC ground bus bar (TB2) in the AC Interface Enclosure.
System Neutral Requirements
The PV100S is designed to be installed as a 4-wire system. As required by the UL 1741 listing, a neutral conductor from the utility-interconnect must be terminated at TB6 within the AC Interface Enclosure to ensure that the AC voltage sensing circuit can perform an individual phase voltage (line-to-neutral) measurement. The function of the neutral connection is to provide a point of reference for measurement purposes that is essentially at ground potential. No power will flow through the neutral conductor.
Utility Side Isolation Transformer Requirements
The PV100S is supplied with a custom, high-efficiency, isolation transformer as part of the AC Interface/Transformer assembly. The utility side windings of the isolation transformer are configured Wye and must match the voltage at the utility inter-tie. The PV100S is a balanced, three-phase, current-sourcing inverter and only operates with the presence of a stable utility voltage. The transformer is also supplied with a neutral connection on the utility interconnect. Connection of this utility-side neutral does not affect the operation of the inverter, however connection of the neutral on the inverter-side does affect the operation and must be left floating or disconnected. Single-phase, grounded loads which may be present between the transformer and utility, will maintain their existing ground reference at the utility distribution transformer.
CAUTION: Equipment Damage
If the Isolation Transformer (T6-X0) neutral terminal is tied to ground, it will cause irreparable damage to the PV100S. Check local regulations for their requirements regarding the connection of the neutral.
WARNING: Lethal Voltage
Grounding the neutral of a Wye-wound transformer may create an “open delta” condition, depending on the utility configuration. This condition may keep the PV100S from detecting a loss of phase condition on the utility system, which may allow potentially lethal voltage to be present on the open-phase wiring.