MidNite Solar String Level SunSpec Rapid Shutdown Receiver for 600VDC Solar Arrays

Description

The MidNite Solar MNSSR-600S-SS is a string-level rapid shutdown receiver that operates using SunSpec power line communication protocol to meet NEC 690.12 safety requirements. Unlike module-level power electronics that control each solar panel individually, string-level shutdown devices control entire series strings of panels from a single point, typically installed at the last module in each string. This approach reduces hardware requirements and installation complexity while providing code-compliant voltage reduction for emergency responder safety.

String-level shutdown differs fundamentally from module-level shutdown in its control architecture. While module-level devices reduce voltage at each individual panel to meet the NEC 2017 requirement of 80V maximum within the array boundary, string-level devices interrupt the entire string circuit when rapid shutdown is initiated. The MNSSR-600S-SS is positioned for installations where the less stringent outside-array-boundary requirements apply, or where UL3741 hazard control systems are implemented, rather than requiring individual module control.

The device operates on a fail-safe principle using SunSpec communication transmitted through the DC conductors from compatible transmitters. When the transmitter signal is lost due to AC power disconnection or manual shutdown initiation, the receiver opens the circuit within 30 seconds. The unit works with all SunSpec-certified transmitters, whether integrated into inverters from manufacturers like SMA, Sol-Ark, and Solis, or standalone transmitters such as MidNite’s MNSST series.

Installation flexibility allows mounting directly to module frames using integrated clips or through-bolt mounting using the tab provision. The NEMA 4X enclosure withstands outdoor exposure from -40°C to +85°C ambient temperature. Operating specifications include 600VDC maximum input voltage, 42VDC minimum operating voltage, and 550VDC maximum MPPT input compatibility. Current capacity rates at 12A continuous at 70°C, maintaining 12A at 80°C, and derating to 10A at 85°C ambient.

The receiver requires no external power supply, drawing operational power from the PV string itself through the approximately 42VDC minimum input requirement. No additional communication wiring or grounding conductors are needed between the transmitter and receivers, eliminating the cost and complexity associated with dedicated control wiring runs across solar arrays. The wireless nature of SunSpec communication through existing DC conductors allows retrofitting into existing installations.

UL3741 and UL1741 listing enables use with Iron Ridge racking systems and various inverter platforms. For residential applications, compatibility includes MNP AIO, Sol-Ark, and Solis inverters. Commercial installations integrate with SMA Tri Power inverters for sloped roofs and SMA Core inverters for flat roof applications. The SS designation indicates optimization for solar shingle installations where compact form factor and flexible mounting are critical.