Rapid shutdown provides a quick and easy method to de-energise solar panels to ensure complete safety for you and first responders in the event of an emergency. Rapid shutdown is mandatory on all solar systems in the United States to reduce fire and electrocution risk, however, in Australia, the standards are yet to adopt this technology.
Solving the fire risk for Australian solar
As most systems sold in Australia are low cost, conventional DC solar, the majority of Australian homes with solar panels do not have safety features such as rapid shutdown technology. Additionally, these DC solar systems installed on homes can generate up to 600 volts of high-voltage DC, which can pose a serious fire risk. It's a lose-lose scenario.
If you are seeking to invest in solar power for your home, know that safe solar systems using fire-safe rapid shutdown technologies are readily available in Australia and make up a growing proportion of all new systems installed. Until Australian standards are changed to mandate the use of safe solar technologies, it is up to you to request that only safe solar equipment be installed. Nobody wants to end up with a system that comes with a fire risk. Understanding the potential dangers now can save you in the long run.
How Rapid shutdown protects your home and business
Rapid shutdown enables current to be stopped or reduced to specific voltage levels within (and outside) of an array boundary. An array boundary is the area around solar conductors.
The rapid shutdown standards adopted in America and other countries stipulate that the voltage levels within solar conductors within 1 foot (305mm) of the boundary should be no more than 80 volts within 30 seconds of shutdown being initiated and that the voltage outside of that boundary should be no more than 30 volts within 30 seconds.
This diagram shows the acceptable voltage levels inside the 1ft (305mm) array boundary (80 V) and outside the array boundary (30 V). Once rapid shutdown has been initiated, the voltage has 30 seconds to reach these levels.
NEC 2017 CODE LANGUAGE (FOR THE TECHNICALLY MINDED)
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.
Controlled Conductors and Limits
N (A) Controlled Conductors. Requirements for controlled conductors shall apply to PV circuits supplied by the PV system.
N (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:
(i) 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.
(ii) 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.
Where is the National Electrical Code (NEC) in effect?
As of 1 July 2020, the 2020 NEC is in effect in four states, the 2017 NEC is in effect in 31 states, the 2014 NEC is in effect in nine states and the 2008 NEC is in effect in three states.