GFCI - Further Reading

Ground-Fault Circuit Interrupters (GFCI)

The Ground Fault Circuit Interrupter continuously monitors the the difference in current between the hot and neutral conductors. If the electricity going to a circuit is equal to the current back from the circuit the GFCI is dormant. If the electricity going to a circuit is greater than 5ma then the current coming back, the GFCI will open the circuit and stop the flow of electricity.

The purpose of the GFCI is to prevent severe electrical shocks. Ground faults occur when the electrical current in an circuit strays outside its normal path, and the human body becomes part of the path through which the electrical current may flow.

National Electrical Code Requirements

The National Electrical Code covers pool requirements in Section 680. The NEC is revised every 3 years and pool requirements have evolved. Below lists the current code requirements:

  • Pool motors require GFCI protection whenever they’re rated 120V, 208V, 240V, 15A or 20A (added in 2008)
  • All electrical outlets must be at least 6 feet from the inside of the wall and must be GFCI protected. (changed in 2017)
  • GFCI protection is required for ALL 15-amp, 20-amp, 125V, or single phase electrical outlets installed within 20 feet from a pool
  • GFCI protection is required for ALL receptacles that supply power to the pool equipment, such as water heaters and pump motors.
  • GFCI Protection is required for ALL underwater lighting operating over the low-voltage contact limit
  • GFCI Protection is required for ALL light switches

GFCI Circuit Breakers

How it Works

The circuit breaker gfci works similarly to a clamp ammeter. For example, if you had L1, L2 and Neutral and you put a 240 volt, 10 amp load on the system, L1 and L2 would each carry 10 amps.[1]

If you measure L1 or L2, you should read 10 amps on each leg. However, if you clamp over both lines at the same time, the current would read zero because the current's magnetic field in the forward direction cancels the current's magnetic field in the reverse direction.[2]

If you then added a 120 volt, 5 amp load, you would measure 15 amps on one hot leg, 10 amps on the other hot leg and 5 amps on the neutral.

A clamp ammeter around any 2 or 3 wires will measure the net difference between current in both directions.

Putting the meter around all 3 wires should cancel and read zero amps.

As long as the neutral goes through the breaker, the total current in both directions should cancel.

So, a breaker doesn't really measure current and compare to make sure that the current is the same. It works on a cancelling effect.

As long as the current in both directions cancels, the breaker won't trip.

GFCI Testing

The The National Electrical Safety Foundations (NESF) and vendors suggest homeowners test their ground fault circuit interrupters (GFCI) every month - especially during thunderstorm season.

Each GFCI circuit breaker or receptacle has a built-in test button to test the device. It is very important to test each and every GFCI in your home once a month. To test a GFCI circuit breaker, make sure the breaker handle is in the "ON" position. Depress the "TEST" button. This will cause the handle to move to an intermediate "tripped" position indicating that the GFCI is functioning properly. Reset your circuit breaker by pushing the handle to the "OFF" position first, then "ON." If the circuit breaker fails to trip, it must be replaced.

GFCI Trips

  • GFCI breakers are doing their job when they trip when sensing a small imbalance. This type of small current imbalance is less then what would trip a regular circuit breaker.
  • Moisture from rain or sprinklers can cause a GFCI to trip
  • Some breakers are less sensitive to electrical noise from transformers, variable speed pumps, and lighting controls. Siemens breakers are recommended by some pool equipment manufacturers to be the least sensitive to false GFCI trips.
  • Keep your pump dry and not sitting in a puddle or area of excess runoff to prevent GFCI trips.