A good friend of mine, who is the chief electrical plans reviewer for a major city, called me the other day. Whenever he calls, I know he has very interesting questions that often require major discussion and may result in some investigation to determine how to apply the National Electrical Code. 

Same requirements as HVAC?

In this most recent phone call, we were  determining if welding receptacles in a commercial garage are required to be GFCI-protected and, if so, whether there would be a problem with nuisance tripping, similar to what has happened with the recent requirement for GFCI protection of air conditioning (HVAC) outlets at dwelling units. 

GFCI protection requirements in 210.8(F), Exception No. 2 have postponed GFCI protection for listed HVAC equipment for dwelling units until Sept. 1, 2026, because there have been problems with nuisance tripping. While tripping of GFCI circuit breakers or receptacles protecting air conditioning units for dwellings in high-heat locations (e.g., in desert areas) can be life-threatening, tripping of GFCI devices for commercial welder outlets, in other than dwelling units, would not be the same threat. However, it could be frustrating at the very least.

NEC 210.8(B) covers all 125V through 250V receptacles supplied by single-phase branch circuits rated at 150V or less to ground and rated at 50A or less, plus all receptacles supplied by three-phase branch circuits rated 150V or less to ground and rated at 100A or less. NEC 210.8(B)(10) requires GFCI protection for these receptacles in commercial garages, accessory buildings, service bays and similar areas. None of the six exceptions located in Section 210.8(B) apply to welder outlets in these areas. 

Scope 630.1

The next reference in the NEC to look at is the scope in 630.1 for welders, which states, “this article covers apparatus for electric arc welding, resistance welding, plasma cutting, and other similar welding and cutting process equipment connected to an electric supply system.” 

The enhanced text in NFPA Link states, “The two general types of electric welding are resistance welding and arc welding. Resistance welding, or ‘spot’ welding, is the process of electrically fusing two or more metal sheets or parts. The metal parts are placed between two electrodes or welding points, and a high current at a low voltage is passed through the electrodes. The resistance of the metal parts to the flow of current heats them to a molten state, and a weld is made. Arc welding is the butting of two metal parts, then striking an arc at the joint with a metal electrode (a flux-coated wire rod). The electrode itself is melted and supplies the extra metal necessary for joining the metal parts.” 

NEC 630.6 requires all welding equipment to be listed. NEC 630.8 requires all 125A, 15A and 20A receptacles for electrical hand tools or portable lighting equipment supplied by single-phase branch circuits rated 150V or less to ground installed in work areas where welders are operated to have GFCI protection for personnel. Again, this does not require the welders to be protected by GFCI. 

Arc welders are probably the most commonly used and may use either AC or DC for the welder output. Constant power and current is often used for manual arc welding. The design for many arc welders is a primary and secondary power source and is key to understanding the text covering grounding of welder secondary circuits. 

NEC 630.15 states that “the secondary circuit conductors of an arc welder, consisting of the electrode conductor and the work conductor, must not be considered as premises wiring for the purpose of applying Article 250.” 

The informational note in this section reads as follows: “Connecting welder secondary circuits to grounded objects can create parallel paths and can cause objectionable current over equipment grounding conductors.” 

This text affects the possibility of GFCI protection and nuisance tripping, since secondary current on the equipment grounding conductor of the branch circuit could cause a GFCI device to trip.

NEC 630.11 and 630.12 permit welder branch circuit conductors to have an ampacity calculated by multiplying the rated primary current given on the welder nameplate by the duty cycle rating in Table 630.11(A) and the overcurrent protective device to be sized at 200% of the rated primary current of the welder. That permits a 30A welder receptacle to be protected at 60A and a 50A welder receptacle to be protected at 100A. 

Based on this information, GFCI protection would probably not be a good idea for a welder circuit.

Ольга Лукьяненко / stock.adobe.com