parallel_fuses
Member
- Location
- US
- Occupation
- EE
In jurisdictions still using the 2017 NEC is UL3741 an acceptable means of hazard control or are module level rapid shutdown devices required?
The following article covers the history and evolution of PV hazard control in the NEC, IAEI Magazine: NEC Rapid Shutdown Requirements and UL 3741. After reading the article, particularly the section below, the way I understand it is that although UL3741 did not exist at the time the 2017 NEC was written, provisions for a future means of hazard control were included in the text and UL3741 is an acceptable method.
What is your interpretation of the 2017 NEC and UL3741, and especially helpful would be any insight on the interpretations you have encountered of AHJs who still use the 2017 NEC? Thank you!
“Of particular relevance to this discussion is Section 690.12(B)(2)(1) of the 2017 NEC, which states, “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,”
This provided a way for PV contractors and installers to comply with the NEC rapid shutdown requirements without having to install MLPEs. To comply with this new “listed array” requirement, PV equipment manufacturers began to have their products evaluated by nationally recognized testing laboratories (NRTLs) for compatibility with PV equipment from other manufacturers. Not many such arrays have been listed to the standard, mostly because the standard was not published by Underwriter’s Laboratories (UL) until December 2020.
In the 2020 NEC, Section 690.12(B)(2)(1) was changed to include a new phrase, “PV hazard control system.” Section 690.12(B)(2)(1) of the 2020 NEC states,
“A PV hazard control system listed for the purpose shall be installed in accordance with the instructions included with the listing or field labeling. Where a hazard control system requires initiation to transition to a controlled state, the rapid shutdown initiation device required in 690.12(C) shall perform this initiation.”
The Exception to 2020 NEC 690.12(B)(2)(1) refers to UL3741, Standard for Photovoltaic Hazard Control.”
The following article covers the history and evolution of PV hazard control in the NEC, IAEI Magazine: NEC Rapid Shutdown Requirements and UL 3741. After reading the article, particularly the section below, the way I understand it is that although UL3741 did not exist at the time the 2017 NEC was written, provisions for a future means of hazard control were included in the text and UL3741 is an acceptable method.
What is your interpretation of the 2017 NEC and UL3741, and especially helpful would be any insight on the interpretations you have encountered of AHJs who still use the 2017 NEC? Thank you!
“Of particular relevance to this discussion is Section 690.12(B)(2)(1) of the 2017 NEC, which states, “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,”
This provided a way for PV contractors and installers to comply with the NEC rapid shutdown requirements without having to install MLPEs. To comply with this new “listed array” requirement, PV equipment manufacturers began to have their products evaluated by nationally recognized testing laboratories (NRTLs) for compatibility with PV equipment from other manufacturers. Not many such arrays have been listed to the standard, mostly because the standard was not published by Underwriter’s Laboratories (UL) until December 2020.
In the 2020 NEC, Section 690.12(B)(2)(1) was changed to include a new phrase, “PV hazard control system.” Section 690.12(B)(2)(1) of the 2020 NEC states,
“A PV hazard control system listed for the purpose shall be installed in accordance with the instructions included with the listing or field labeling. Where a hazard control system requires initiation to transition to a controlled state, the rapid shutdown initiation device required in 690.12(C) shall perform this initiation.”
The Exception to 2020 NEC 690.12(B)(2)(1) refers to UL3741, Standard for Photovoltaic Hazard Control.”