A pragmatic guide to PVRSS compliance, array types, and integrating the SunHopper®-D.
As the industry transitions to zero-interconnection direct PV-to-thermal systems, installers often face confusion regarding National Electrical Code (NEC) 690.12 requirements. Rapid shutdown rules exist to protect first responders by quickly de-energizing rooftop solar conductors during an emergency.
Because the SunHopper®-D operates without a complex utility grid interconnection, solar contractors frequently ask how to design a compliant rapid shutdown system (PVRSS). This guide breaks down exactly when rapid shutdown is required, what type of disconnect is necessary, and how the SunHopper®-D integrates with these safety standards.
The necessity and complexity of your rapid shutdown architecture depend entirely on where the photovoltaic (PV) array is physically located.
Any solar array mounted on a residential or commercial dwelling requires full NEC 690.12 compliance. The conductors must be de-energized both inside and outside the array boundary within 30 seconds of initiation. This strictly requires Module-Level Rapid Shutdown (MLRSD).
Because ground mounts are not attached to a dwelling, they typically do not pose the same roof-access risks to firefighters. In most jurisdictions, ground arrays are exempt from module-level shutdown. A simple DC disconnect located at the array or before the conductors enter the home is sufficient.
Attached: If structurally attached to the main home, inspectors classify it as a roof structure, requiring module-level shutdown.
Detached: Freestanding, uninhabited structures are often treated similarly to ground mounts (simple DC disconnect). Always verify with your local AHJ.
When the NEC mandates rapid shutdown for a rooftop array, the rules change depending on exactly where the wires are located in relation to the solar panels. The code defines the "array boundary" as exactly 1 foot from the array in all directions. When a shutdown is initiated, the system has 30 seconds to meet two distinct voltage limits:
30 Volts or less within 30 seconds
Applies to conductors located more than 1 foot away from the panels (such as wires running across the roof deck or down the side of the house).
80 Volts or less within 30 seconds
Applies to conductors located within that 1-foot perimeter (directly under or between the solar panels).
A simple DC disconnect switch mounted on the side of the house can easily de-energize the wires outside the boundary. However, a ground-level switch cannot stop the panels themselves from producing high voltage up on the roof. This 1-foot boundary rule is exactly why Module-Level Rapid Shutdown (MLRSD) receivers must be installed directly on the back of each panel for any roof-mounted array.
Understanding the difference between these two approaches saves time and unnecessary hardware costs.
This involves installing a smart receiver at every single solar panel. These receivers listen for a continuous "keep-alive" signal usually sent via Power Line Communication (PLC) from a transmitter. If the signal stops, the receiver disconnects the panel from the string. Self-Powered Control devices can also be used where a separate switch wire disables each module.
This is a manual, physical switch that breaks the circuit. When flipped, it stops the flow of power from the array to the SunHopper®-D, isolating the electrical hazard without requiring smart electronics at the panel level. (Always verify with your local Authority Having Jurisdiction).
As an Original Equipment Manufacturer (OEM) of solar inverters, GreenPWR® designed the SunHopper®-D for simplicity and compatibility. When designing your safety architecture, it is critical to understand the specific hardware capabilities of the SunHopper®-D:
To meet PVRSS safety limits, the SunHopper®-D is engineered to automatically discharge the PV line capacitance down to safe voltage levels (typically under 30V) within 30 seconds of an emergency shutdown initiation.
The SunHopper®-D does NOT contain an internal rapid shutdown PLC transmitter.
If your installation requires module-level rapid shutdown (e.g., a rooftop array), the SunHopper®-D simply pairs with a standard, off-the-shelf external transmitter. This modular approach allows contractors to use the rapid shutdown hardware they already know and trust.
The power source dictates how your rapid shutdown transmitter operates.
Even though the SunHopper®-D solar array does not export power to the grid, the home itself has utility power.
For remote properties aiming for complete domestic hot water self-sufficiency independent of grid infrastructure, this introduces a classic electrical problem. Module-level receivers on the roof default to the "off" position until they receive a continuous "keep-alive" signal. In a true off-grid setup, if the transmitter relies on the main solar array for power, it can never turn on to send the signal because the array is already shut down.
You can completely bypass complex PLC transmitters and external power supplies by specifying a hardwired rapid shutdown system designed specifically for off-grid simplicity (similar to architectural concepts used by IMO FireRaptor or Projoy Electric).
In this setup, the roof-mounted receivers steal a tiny, imperceptible amount of power directly from the single solar panel they are attached to. These units are then daisy-chained together via a dedicated low-voltage control line that runs down to a simple, independent dry-contact switch at ground level. Because the system generates its own control voltage from the array, there is zero need for an external power supply, batteries, or inverters.
If using standard PLC receivers (like Tigo), bypass the main array entirely for the rapid shutdown system by specifying a low-voltage DC variant of the transmitter. To power it, you can either utilize an existing off-grid battery setup (if available from another system on the property) or install a small, independent 12V solar panel paired with a basic battery charger and a small DC battery. This isolates the safety circuit and ensures the transmitter always has a reliable, independent power source.
The simplest solution is often architectural.
Utilizing a ground mount or detached structure generally qualifies the system for a simple DC disconnect exemption, neatly sidestepping the MLRSD dilemma and eliminating the need for extra transmitters or batteries altogether.