Summary: Informal testing results from Trane shows GFCI outlets or disconnects severely effect variable capacity equipment (ECM / brushless rotor motors / inverter technology). Single speed and two speed equipment has proven to be less susceptible to nuisance trips. This is good news, but much more work needs to be done.

At its April 14, 2021 web-meeting, the ACCA Codes Subcommittee heard an update from a Trane Technologies representative regarding their internal investigation of nuisance trips related to various types of HVAC equipment installed with GFCI protection. The occurrence of GFCI nuisance trips is becoming more widespread as more jurisdictions enforce a new requirement in the 2020 National Electrical Code (NEC), as shown below.

210.8(F) Outdoor Outlets. All outdoor outlets for dwellings, other than those covered in 210.8 (A)(3), Exception to (3), that are supplied by single-phase branch circuits rated 150 volts to ground or less, 50 amperes or less, shall have ground-fault circuit-interrupter protection for personnel.

Trane reported that they have tested HVAC equipment from 6 manufacturers using GFCIs from 4 manufacturers. According to their study, GFCI trips occurred more often for equipment using variable speed motors, referred to as “electronically commutated motors” or ECMs. Although the GFCIs tripped on some constant torque motor (CTM) equipment, there appeared to be fewer trips on equipment using single or two speed CTMs.

The GFCI manufacturers are working on a solution to alleviate the above situation, which will result in changing the UL 943 standard for certifying those devices. After that, the devices will have to be tested and certified, which may also lead to changes to the UL standard for residential air conditioners and heat pumps, UL 60335-2-40. It appears that this activity will take several years to complete and certify.

Recently, the Air-Conditioning, Heating, and Refrigeration Institute (AHRI) submitted a proposed Tentative Interim Amendment (TIA) #1564 to the 2020 NEC, to delay the effective date for 210.8(F) until January 1, 2023. The proposed TIA is specifically for ducted or ductless mini-split and multi-split HVAC equipment using variable speed drive to control compressor speed. ACCA has submitted a letter to NFPA supporting the TIA, based on the Codes Subcommittee’s position on a similar proposal last year. The proposed TIA has a comment due date of April 28, 2021.

The Codes Subcommittee continues to encourage ACCA members to request their jurisdictions to delete the above requirement if and when they consider adopting the 2020 NEC as their state or local code. The template can be found at TEMPLATE_FOR_DELETING_GFCI_FROM_NEC_2.pdf (higherlogicdownload.s3.amazonaws.com).

An update on which states have adopted (or are adopting) the 2020 NEC as of April 1 can be found at the link shown below. So far only Massachusetts and Utah have deleted the above requirement from their electrical codes.

https://www.nfpa.org/NEC/NEC-adoption-and-use/NEC-adoption-maps