240 V and 600 V NEMA 3R Safety Switch Disconnects
The National Electric Code, section 690.15, requires PV arrays to have a disconnecting means to isolate the inverter from the PV power source. Utility grid-tie inverters that utilize PV arrays with voltages above 250 VDC require a 600 VDC rated disconnect to perform this function. For inverters that do not include a DC disconnect, one of these can be used. The Square-D 600 VDC 30, 60, and 100 A 3-pole
safety switches are rated by the factory to handle one 600 VDC circuit per pole. The 30 A switch is rated for 15 A Isc for non-fused and 12.8 A Isc for fused. The 60 A switch is rated for 48 A Isc for non-fused and 38 A Isc for fused. The 100 A switch is rated for 80 A Isc for non-fused and 64 A Isc for fused. They can be used for disconnecting up to 3 PV arrays for 3 grid-tie inverters. All of the Square-D 600 VDC disconnects are rated for disconnecting one circuit at full rated power using 2 poles in series.
Many utilities require an AC disconnect between a grid-tie inverter and the AC load center, close to the AC service entrance, and with a visible and lockable handle. A 30 A /240 V disconnect works for up to 5 kW at 240 VAC and the 60 A disconnect works for up to 11 kW. Use an AC load center to connect multiple inverters to a single disconnect. The breakers can be back-fed with the inverter outputs and the load center main lugs will handle the combined outputs to be connected to the AC disconnect. Use Class R fuses of the proper voltage and amperage for fused disconnects. 600 V fuses will not fit into 240 V disconnects, and 250 VAC/125 VDC fuses will not fit into 600 V disconnects.