ACCA Adds Colorado and Massachusetts Tripping Reports to Its NEC GFCI Appeal
One Boulder-area contractor put direct troubleshooting costs at about $1,300. NFPA's Code-Making Panel 2 split 10-10 on the technical merit of TIA 1924, which would extend the HVAC exception to Sept. 1, 2028.
The Air Conditioning Contractors of America sent the National Fire Protection Association new contractor reports of GFCI breakers tripping on heat pumps in Colorado and Massachusetts, in a supplemental filing dated Oct. 22 in its appeal over Section 210.8(F) of the National Electrical Code. David Bixby, ACCA's manager of codes, described the filing in a Nov. 4 post. NFPA's Standards Council is scheduled to consider the appeals in conjunction with its Dec. 15-16 meeting.
The dispute centers on Exception No. 2, which kept GFCI protection off listed HVAC equipment at dwellings until it expired on Sept. 1. Tentative Interim Amendment 1924, submitted by Thomas Deary of the Air-Conditioning, Heating, and Refrigeration Institute, would move that date to Sept. 1, 2028, in the 2020, 2023 and 2026 editions of the code. ACCA says Code-Making Panel 2 rejected the TIA on technical merit and on emergency nature, with the technical vote split 10-10, while the NEC Correlating Committee approved it on correlation. AHRI's own appeal raises procedural objections, among them an NFPA staff request that AHRI seek resolution with GFCI manufacturers before the TIA moved forward, while ACCA's argues the technical and field questions.
Boulder and MetroWest Trips
In Colorado, an electrical contractor reported unwanted trips on several heat pump installations around Boulder, involving equipment from different manufacturers and breakers from several makers, and some systems tripped repeatedly and lost heat. The contractor put direct troubleshooting and correction costs at about $1,300, excluding administrative time. In Massachusetts, an electrician reported repeated trips on a heat pump in the MetroWest area that continued after the breaker was replaced. ACCA wrote that the reports "do not conclusively establish the cause of every trip."
A 60-Hertz Mechanism in AHRI's Lab Data
The TIA's substantiation draws on AHRI Report No. 8029, research with the Electric Power Research Institute whose Phase II testing finished in early 2026. Preliminary results cited there link part of the problem to high-frequency leakage current from inverter equipment, especially during startup. The testing also turned up a fundamental-frequency path: when a contactor interrupted only one leg feeding the inverter and its filter network, the common-mode choke could behave like a transformer and drive current through line-to-ground filter components, with large current spikes when the contactor closed. A manufacturer-approved component substitution at the equipment front end cured the test unit, but AHRI wrote that the findings had not yet been shared with all manufacturers. GFCI devices also varied widely in how they responded to high-frequency differential current.
The 60-hertz finding bears on the high-frequency rated breakers now offered as the fix. UL's Supplement SB to UL 943 tests GFCI immunity to high-frequency signals, and the 2026 NEC recognizes HF and HF+ devices in an informational note to 210.8(F). In an Oct. 20 post, ACCA said an HF designation "does not mean every possible cause of unwanted HVAC GFCI tripping has been eliminated." Its new filing also cites leakage from electronically commutated fan motors, a source that exists in single-stage equipment as well as inverter units.
Roughly 22 States Have Delayed or Dropped the Rule
ACCA's GFCI resource page, updated Nov. 4, says roughly 22 states have delayed or deleted the requirement. Minnesota enforces it on new construction only and exempts replacements where the feeder or branch circuit is not altered or extended. Dean Hunter, assistant director and chief electrical inspector at the Minnesota Department of Labor and Industry, told ACCA the state had received no reports of HVAC GFCI compatibility problems since Sept. 1 and was seeing significant use of HF devices. Before the exception expired, Minnesota allowed GFCI protection to be removed once an unwanted-tripping report had been filed with the National Electrical Manufacturers Association. It has no comparable procedure now and will handle incidents case by case.
Why This Matters to Contractors
The last 210.8(F) fight before the Standards Council ended with a split result. At its August 2021 meeting the council denied appeals seeking TIAs 1564 and 1589 to the 2020 code, issued TIA 1593 because it had cleared Panel 2 and the Correlating Committee, and told NFPA staff to form a task group of HVAC, mini-split and GFCI manufacturers. TIA 1924 has the Correlating Committee's vote but not the panel's, so December's ruling will show whether the council will issue an extension its technical panel did not pass. Until then, the exception is gone wherever a jurisdiction enforces the code as written.
Sources
- David Bixby, ACCA, "Tip of the iceberg? New HVAC field reports strengthen ACCA's GFCI appeal," Nov. 4, 2026. hvac-blog.acca.org
- David Bixby, ACCA, "ACCA appeals NFPA ruling on GFCI nuisance tripping," Sept. 25, 2026. hvac-blog.acca.org
- David Bixby, ACCA, "Outdoor HVAC GFCI requirement: what Minnesota is seeing," Oct. 20, 2026. hvac-blog.acca.org
- ACCA, "Outdoor HVAC GFCI Requirements and State Guidance," updated Nov. 4, 2026. acca.org
- NFPA, Proposed TIA Log No. 1924 to NFPA 70, 210.8(F) Exception No. 2, comment closing date Sept. 9, 2026. nfpa.org
- EC&M, "NFPA Makes Ruling on Three TIAs Related to Sec. 210.8(F) of 2020 NEC," Sept. 24, 2021. ecmweb.com