Understanding GFCI nuisances
Since the expansion of the 2017 National Electrical Code (NEC) ground fault circuit interrupter (GFCI) requirements to include single-phase receptacles up to 50A and three-phase receptacles up to 100A, we’ve seen a trend of increased GFCI nuisance tripping.
Since the expansion of the 2017 National Electrical Code (NEC) ground fault circuit interrupter (GFCI) requirements to include single-phase receptacles up to 50A and three-phase receptacles up to 100A, we’ve seen a trend of increased GFCI nuisance tripping. While these trips can be frustrating, it’s important to not create a code violation or put personnel at risk by removing GFCI protection. Often, a tripping GFCI device may be operating properly; it’s possible there is an equipment or wiring issue that needs to be addressed.
At Henderson Engineers, we’ve compiled the following information to help our clients understand why they may be experiencing an issue and suggestions on how to address it.
What is GFCI protection?
GFCI devices have been credited with saving numerous lives since their introduction to the NEC in 1971. This protection can be achieved via a GFCI circuit breaker or a GFCI receptacle. These devices reduce electrocution risks by measuring the electrical current between the phase conductor and the neutral return. If the return current differs by more than 4 to 6 mA, a dangerous amount of current is flowing somewhere it shouldn’t be – so the device shuts off. Per the 2017 NEC, GFCI protection is required in bathrooms, kitchens, rooftops, outdoors, within 6’ of a sink, and select other areas.
The NEC commentary explains that they expanded GFCI requirements to include higher voltages and current ratings because equipment connected to those receptacles present the same shock hazards as those of lower voltages and current ratings. Unfortunately, this expansion of the GFCI requirements has led to more nuisance tripping and owner’s asking, “Why is my GFCI not working?”
Common Causes of GFCI Trips
1. There are too many appliances being protected by the GFCI.
Sometimes tripping occurs when a GFCI circuit breaker is protecting multiple downstream receptacles. If several appliances are connected to the GFCI device, the cumulative effect of the appliance leakage currents may trip the GFCI. To ensure proper operation, minimize the number of appliances protected by the GFCI. Depending on the circuit length from the GFCI sensing device, it may be necessary to limit the number of appliances being protected to one or two.
2. The circuit is too long for the equipment being protected by the GFCI.
This is common in GFCI circuit breakers with circuit lengths over 150’. Capacitive leakages due to the wire length of the circuitry may exceed the threshold of the GFCI. (The actual length limitations vary depending on wire type and size.) To prevent this issue, place the GFCI device close to the equipment it will be protecting – this may mean using a GFCI receptacle or blank face GFCI device near a normal receptacle.
3. The GFCI was improperly wired by an electrician.
Have the installation checked to see if the GFCI receptacle and related circuitry are installed correctly. Verify the neutral is dedicated and connected to the correct circuit, etc. While testing of GFCI devices is not generally included in the basic scope of commissioning services, having a trusted third-party electrician or commissioning agent provide independent verification of proper installation may be necessary.
4. The area is too wet.
If nuisance tripping is occurring in areas near dishwashing, mop sink, janitorial, ice machines, showers, walk-in coolers, exterior locations, roofs, and other areas with a lot of condensation, then too much moisture may be the cause. Check to see if there are any environmental or operational changes that can be made to reduce moisture near the appliance and receptacle. Installing a weatherproof cover plate at the receptacle may be helpful.
5. An appliance may have manufacturing defects.
It’s possible an appliance may be leaking too much current to ground. Appliances are allowed a certain amount of leakage current per their UL listings; acceptable maximums may be as high as .75mA per appliance. Unfortunately, some equipment may not be built to the same standards as the prototype that passed testing. Now that more receptacles are required to have GFCI protection, equipment issues may be coming to light. If you have faulty equipment, contact the equipment supplier/manufacturer for repair or replacement.
6. The GFCI device may be defective.
These devices don’t last forever, and some are defective even when new. UL 943 covers Class A GFCI devices. GFCI breakers and receptacles should be replaced in accordance with manufacturer’s recommendations. Best practice is to test GFCIs monthly and replace them every 5 years.
GFCI devices trip for several reasons. The following best practices can help confirm proper operation and reduce nuisance tripping.
- Minimize the number of appliances protected by each GFCI.
- Minimize the circuit length from the GFCI circuit breaker to the receptacle – a maximum conductor length of 150’ is good rule of thumb.
- Verify GFCIs are installed per manufacturer’s recommendations and as required per code.
- Avoid excessive moisture around appliances and receptacle.
- Replace defective appliances.
- Replace defective or GFCI devices that are more than 5 years old.
- Maintain easy access to GFCI devices in case they need to be reset. (The 2017 NEC requires GFCI receptacles to be “Readily Accessible.” That means one must be able to reach the device quickly, without having to use ladders or climbing over obstacles, like large stationary kitchen equipment. GFCI breakers or blank face GFCI devices are sometimes needed to meet this requirement.)
Although they can be frustrating, it’s important to remember, GFCI devices have been proven to save lives and are required by code. Proper application and maintenance of these devices is essential for personnel safety and smooth business operations. If you’re experiencing GFCI issues our team can help, contact us for more information.
Original content can be found at www.hendersonengineers.com.