What is Rapid Shutdown?

690.11 Arc-Fault Circuit Protection (Direct Current).

Photovoltaic systems operating at 80 volts dc or greater between any two conductors shall be protected by a listed PV arc-fault circuit interrupter or other system components listed to provide equivalent protection. The system shall detect and interrupt arcing faults resulting from a failure in the intended continuity of a conductor, connection, module, or other system component in the PV system dc circuits.

• Informational Note: Annex A includes the reference for the Photovoltaic DC Arc-Fault Circuit Protection product standard.

Exception: For PV systems not installed on or in buildings, PV output circuits and dc-to-dc converter output circuits that are direct buried, installed in metallic raceways, or installed in enclosed metallic cable trays are permitted without arc-fault circuit protection. Detached structures whose sole purpose is to house PV system equipment shall not be considered buildings according to this exception.

690.12 Rapid Shutdown of PV Systems on Buildings.

PV system circuits installed on or in buildings shall include a rapid shutdown function to reduce shock hazard for emergency responders in accordance with 690.12(A) through (D).

• Exception: Ground mounted PV system circuits that enter buildings, of which the sole purpose is to house PV system equipment, shall not be required to comply with 690.12.

(A) Controlled Conductors.

Requirements for controlled conductors shall apply to PV circuits supplied by the PV system.

(B) Controlled Limits.

The use of the term array boundary in this section is defined as 305 mm (1 ft) from the array in all directions. Controlled conductors outside the array boundary shall comply with 690.12(B)(1) and inside the array boundary shall comply with 690.12(B)(2).

(1) Outside the Array Boundary.
Controlled conductors located outside the boundary or more than 1 m (3 ft) from the point of entry inside a building shall be limited to not more than 30 volts within 30 seconds of rapid shutdown initiation. Voltage shall be measured between any two conductors and between any conductor and ground.

(2) Inside the Array Boundary.
The PV system shall comply with one of the following:
(1) The PV array shall be listed or field labeled as a rapid shutdown PV array. Such a PV array shall be installed and used in accordance with the instructions included with the rapid shutdown PV array listing or field labeling.
Informational Note: A listed or field labeled rapid shutdown PV array is evaluated as an assembly or system as defined in the installation instructions to reduce but not eliminate risk of electric shock hazard within a damaged PV array during fire-fighting procedures. These rapid shutdown PV arrays are designed to reduce shock hazards by methods such as limiting access to energized components, reducing the voltage difference between energized components, limiting the electric current that might flow in an electrical circuit involving personnel with increased resistance of the conductive circuit, or by a combination of such methods.
(2) Controlled conductors located inside the boundary or not more than 1 m (3 ft) from the point of penetration of the surface of the building shall be limited to not more than 80 volts within 30 seconds of rapid shutdown initiation. Voltage shall be measured between any two conductors and between any conductor and ground.
(3) PV arrays with no exposed wiring methods, no exposed conductive parts, and installed more than 2.5 m (8 ft) from exposed grounded conductive parts or ground shall not be required to comply with 690.12(B)(2).

The requirement of 690.12(B)(2) shall become effective January 1, 2019.

(C) Initiation Device.

The initiation device(s) shall initiate the rapid shutdown function of the PV system. The device “off” position shall indicate that the rapid shutdown function has been initiated for all PV systems connected to that device. For one-family and two-family dwellings, an initiation device(s) shall be located at a readily accessible location outside the building.

The rapid shutdown initiation device(s) shall consist of at least one of the following:
(1) Service disconnecting means
(2) PV system disconnecting means
(3) Readily accessible switch that plainly indicates whether it is in the “off” or “on” position

Informational Note: One example of why an initiation device that complies with 690.12(C)(3) would be used is where a PV system is connected to an optional standby system that remains energized upon loss of utility voltage.

Where multiple PV systems are installed with rapid shutdown functions on a single service, the initiation device(s) shall consist of not more than six switches or six sets of circuit breakers, or a combination of not more than six switches and sets of circuit breakers, mounted in a single enclosure, or in a group of separate enclosures. These initiation device(s) shall initiate the rapid shutdown of all PV systems with rapid shutdown functions on that service. Where auxiliary initiation devices are installed, these auxiliary devices shall control all PV systems with rapid shutdown functions on that service.

(D) Equipment.

Equipment that performs the rapid shutdown functions, other than initiation devices such as listed disconnect switches, circuit breakers, or control switches, shall be listed for providing rapid shutdown protection.

Informational Note: Inverter input circuit conductors often remain energized for up to 5 minutes with inverters not listed for rapid shutdown.

Section 605.11.1 governs marking electrical assemblies containing DC conductors in both interior and exterior locations to help emergency personnel quickly identify (and shut down) energized sources, which could pose a shock hazard. These requirements mirror the requirements set in Section 690.31(G) of the 2014 NEC. All raceways, enclosures, junction boxes, cable assemblies, combiners, and disconnects need to be clearly labeled to indicate the presence of PV conductors. The labels shall have “WARNING: PHOTOVOLTAIC POWER SOURCE” in all-white, capital letters, a minimum of 3/8 inch tall, on a red background. These labels must be reflective and weather-resistant.

IFC mandates the marking locations on all interior and exterior raceways, enclosures, and cable assemblies. This labeling has the added benefit of helping ensure the conductors won’t be confused with those from a different electrical system, like an AC circuit that could be used to run a new load. This section’s labeling must be applied:

• Every 10 feet
• Within 1 foot of turns or bends
• Within 1 foot of penetrations through roofs/ceilings, walls, or other barriers

Section 605.11.2 specifies the locations for DC conductors—to minimize trip hazards for firefighters and not obstruct potential areas for ventilation access. The IFC accomplishes this by requiring PV circuit raceways be run as close as possible to the roof’s ridge, hip, or valley. Raceway transitions from a hip or valley should take the shortest/most direct path to an exterior wall. If combiners or junction boxes are used for multiple subarrays, they should be installed and connected in a manner that minimizes raceways on any pathways and that keeps the raceways as short as possible. As with the NEC, metallic conduit or raceways are required for DC circuits located inside buildings.

The next section, 605.11.3 Access and Pathways, can be the most challenging section of 605.11 to meet, although local AHJs may allow exceptions. Section 605.11.3.2.4 governs roof access for smoke ventilation, and is applicable to all rooftop installations, regardless of roof type. To meet this section’s requirements, modules must be installed at least 3 feet below a roof’s ridge. Since this is not a pathway requirement, the space doesn’t have to be clear of obstructions.

The array cannot block access to the roof for firefighters attempting to gain access from the ground. Available roof access points must be able to support a firefighter’s load and not be located directly in front of windows and doors. For the pathway requirements, the IFC establishes rules for three specific roof layouts: hip, gable, and hip-and-valley. These rules apply to roof slopes greater than 2:12 pitch and require the pathways to be located over structurally supported areas that can support the live load of a firefighter.

For hip roof layouts, 605.11.3.2.1 requires a single 3-foot-wide, clear pathway from ridge to eave on each slope where modules are located. Buildings with a single roof ridge (aka gable) are covered under 605.11.3.2.2, which requires two 3-foot-wide, clear pathways from ridge to eave on each slope where modules are installed. The exact location for each pathway is not defined; typically, the most convenient location will be on outer edges of the roof as long as they are structurally supported.

Pathway requirements for buildings with hips and valleys are detailed in 605.11.3.2.3. These complex roof shapes can make meeting the Code difficult. They must have at least one 3-foot-wide, clear pathway from ridge to eave on the slope that has modules, regardless of what is on the other side of the roof. If there are modules on both sides of the hip or valley, then a minimum 18-inch pathway needs to be provided on both sides of the hip or valley (to create a 3-foot-wide pathway). If the other side of the hip or valley is without modules, the PV array can go all the way to the hip or valley.

Code references:

• National Fire Protection Association – NFPA 70
• 2017 National Electrical Code – NEC, Article 690.12
• OSHA Standards – 1926 Subpart K – Electrical
• 2012/2015 International Fire Code (605.11)