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How to comply with solar rapid shutdown requirements

By SPW | May 8, 2017

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See also: How to meet NEC 2017 rapid shutdown requirements


NEC 2014
PV rapid shutdown requirements were added to NEC 2014 (690.12) to improve electrical and fire safety hazards for first responders. System conductors may remain energized even after the electrical service disconnect has been opened. To alleviate this risk, the NFPA has published specific requirements to de-energize conductors extending from a PV array.

PV system circuits installed in or on buildings must include a rapid shutdown function in accordance with NEC 2014, Article 690.12.

Conductors that extend greater than 10 ft from the array (outside) or more than 5 ft inside a building are required to be de-energized upon command of shutdown. These conductors must be de-energized to below 30 and 240 Vac within 10 seconds of initiating rapid shutdown.

Correct stickers or signage should identify the rapid shutdown initiation method, and all PV equipment performing the rapid shutdown shall be listed and identified.

NEC 2017
As states and local authorities begin to adopt the 2017 edition of the NEC, it’s important to review the revisions to Section 690.12. While the complete scope of revisions is beyond the scope of this article, a notable revision is that for “array-level” rapid-shutdown compliance, 690.12(B) redefines the term array boundary to be 1 ft from the array in all directions. This is a reduction from the 10-ft boundary of the 2014 edition.

NEC 2017 690.12(B)(2) also introduces requirements for de-energizing controlled conductors inside of the array boundary. This requirement will be not be required until January 1, 2019.

PV equipment location should be carefully considered when installing a rapid-shutdown-compliant system. Below are examples on how compliance can be achieved for systems of various sizes.

Residential PV systems:
For a residential system, rapid shutdown compliance can be achieved by the following means:

  • Use of a rapid-shutdown-complaint combiner installed within 10 ft of the array to de-energize conductors extending from the array to the inverter
  • Inverter installed indoors with no more than 5 ft of conductors inside the building
  • Inverter installed outside within 10 ft of the array

Commercial PV systems (string inverters):
For commercial systems, rapid shutdown compliance can be achieved by the following means:

  • Use of a rapid-shutdown-compliant combiner installed within 10 ft of the array to de-energize conductors extending from the array to the inverter
  • Three-phase string inverter installed within 10 ft of array (equipment outside) or within 5 ft of array (equipment inside)

When designing a rapid-shutdown-compliant system, consider the DC bus capacitance inherent of PV inverters. The natural discharge time of this circuity may exceed the de-energization requirements of 690.12 for the DC output conductors. Please inquire with your equipment providers for additional information.

Utility PV systems (central inverters):
For utility projects or systems using three-phase central inverters, rapid-shutdown compliance is achieved through rapid-shutdown-compliant combiner boxes installed at the array.

Installation tip was provided by Michael Nieman, applications engineer, Yaskawa – Solectria Solar

Comments

  1. Daniel Cruz says

    July 28, 2020 at 10:13 am

    How would you conduct testing of the Rapid Shutdown once installed and what would you be looking for acceptance of operation?

    Reply
  2. James Nunes says

    March 4, 2020 at 2:07 am

    I was told by my Solar installer that my new in box Sunpower SPR-4000f string tie inverter could not be used in CA after 2020. Due to the Rapid shutdown having to be built into the system… and that there was no UL approved way of doing outside the inverter. Any cost effective ideas?

    Reply
  3. david b khoury says

    February 22, 2020 at 12:19 pm

    who shuts it down? the homeowner or first responders?

    Reply
    • Kelsey Misbrener says

      February 24, 2020 at 8:52 am

      Probably first responders in most instances.

      Reply
  4. Ian Boake says

    September 21, 2019 at 6:38 am

    What does a contactor for 240VA and on the DC circuits add to the costs?

    Reply
  5. Daniel Woodring says

    April 12, 2019 at 10:29 pm

    NEC 690.12 alludes to the 10ft./5 foot rule. If a combiner box located on the outside wall is less than 10 feet from the roof-top array, does there need to be Rapid Shutdown? Would a charge controller, rather than an inverter, located inside the building just behind the combiner box require rapid shutdown?

    Reply
  6. joe says

    January 22, 2019 at 6:31 pm

    the one sentence people come to view is the definition of rapid shut down requirements , however the most important definiton is not clear.
    “These conductors must be de-energized to below 30 and 240 Vac within 10 seconds of initiating rapid shutdown.”
    So what does “below 30” mean ? 30% or 30 Watts or 30 Amps or is it AC or DC values …what is the “30” ?

    Reply
    • Kelly Pickerel says

      January 23, 2019 at 7:21 am

      It’s 30 volts and 240 volt-amperes

      Reply
    • Patrick says

      January 21, 2021 at 6:12 pm

      30 volts DC. Houses are already allowed to have 240 AC everywhere.

      Reply

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