How do you use a GFCI breaker on 208 volt single phase 50 amp equipment?

This comes up constantly on commercial kitchen equipment, booster heaters, and fryers. The equipment is 208 volts single phase, pulled from two phases of a 208Y/120 panel, and it has no neutral. People assume a GFCI breaker will not work because there is nothing to land on the load neutral terminal. It works fine.

The pigtail versus the load neutral

A two pole Class A GFCI breaker has two terminals that matter here. The white curly pigtail is the breaker panel neutral connection and it always lands on the panelboard neutral bar. That pigtail powers the electronics and gives the trip circuit a reference. Separately there is a load neutral terminal on the breaker body. If your equipment has no neutral, you leave that terminal empty and torque it down on nothing.

The current transformer inside the breaker senses the vector sum of everything passing through it. With two ungrounded conductors and no neutral, the sum is zero under normal operation and any imbalance is fault current returning through the equipment grounding conductor or a person. That is exactly what you want.

Voltage rating on a 208Y/120 system

Check the breaker marking. Section 240.85 permits a circuit breaker marked with a slash rating such as 120/240 volts to be used where the nominal voltage between any conductor and ground does not exceed the lower value and the nominal voltage between any two conductors does not exceed the higher value. On a 208Y/120 system, line to ground is 120 volts and line to line is 208 volts, both inside a 120/240 volt marking. A standard two pole 50 ampere 120/240 volt GFCI breaker is acceptable.

What is not acceptable is putting that same slash rated breaker on a 240 volt corner grounded delta or an ungrounded delta, where line to ground can reach the full line to line value. Those need a straight 240 volt or 480 volt rated device.

Class A versus equipment protection

A Class A GFCI trips at 4 to 6 milliamperes and is what 210.8 and 422.5 mean when they say ground fault circuit interrupter protection for personnel. Long feeders and equipment with line filters, heating elements, or variable frequency drives leak enough capacitive current to nuisance trip a Class A device at 50 amperes.

If the equipment only requires ground fault protection of equipment, a 30 milliampere GFPE device is the right tool. Section 427.22 requires it for pipeline and vessel heating, and 426.28 for de icing and snow melting. Do not swap a GFPE in where the code text says protection for personnel, and do not swap a Class A in where the manufacturer instructions call for GFPE.

Which 208 volt loads actually require it

Section 210.8(B) applies to receptacles rated 150 volts to ground or less and 50 amperes or less in the listed commercial locations, and 208 volt single phase receptacles fed from a wye system are 120 volts to ground, so they are in scope. Section 422.5(A) lists specific hardwired appliances that require GFCI protection including dishwashers, electric ranges, wall mounted ovens, and clothes dryers, and 422.5(B) permits the protection to be a branch circuit breaker, a receptacle, or a listed device.

Field takeaway

Two pole Class A GFCI breaker, pigtail on the neutral bar, load neutral terminal empty. Confirm the breaker is slash rated 120/240 volts and the system is 208Y/120. If the load nuisance trips a Class A device and the code only requires equipment protection, move to a 30 milliampere GFPE.