Two different kinds of protection
A standard breaker protects the wire from overheating. It does not react to small currents that can hurt a person, and it can miss the sparking from damaged wiring that starts fires. Two other devices fill those gaps.
- GFCI (ground fault circuit interrupter) protects people from shock. It trips when even a small amount of current leaks to ground, for example through a person standing on a wet floor.
- AFCI (arc fault circuit interrupter) protects against fire. It recognises the electrical signature of arcing in damaged cords and wiring and trips before the arc can ignite anything.
You will see both as receptacles with TEST and RESET buttons, or as breakers in the panel with a test button. Some newer breakers combine both functions.
How a GFCI works
In a healthy circuit, all the current that goes out on the hot conductor comes back on the neutral. A GFCI measures both. If a few thousandths of an amp are missing, that current is going somewhere it should not, possibly through a person, and the GFCI cuts power in a fraction of a second.
That is why GFCI protection is required in wet and damp locations. In a typical newer Alberta home, you will find it on bathroom receptacles, receptacles near kitchen and laundry sinks, outdoor receptacles and often in garages and unfinished basements. Requirements have grown with each code edition, so older homes may have less.
How an AFCI works
Arcing happens when current jumps a gap: a cable nicked by a picture-hanging nail, a cord crushed under furniture, or a connection that has worked loose. Arcs can be hot enough to ignite wood framing and insulation without drawing enough current to trip a normal breaker.
An AFCI breaker watches the current waveform for the ragged pattern of arcing and trips when it sees it. The Canadian Electrical Code now requires arc-fault protection on most receptacle circuits in new dwelling units, with some exceptions. Exactly which circuits depends on the code edition in force when the work was permitted.
Where to find them in your home
One GFCI receptacle can protect other ordinary-looking receptacles downstream of it. If a bathroom or outdoor receptacle is dead and no breaker has tripped, look for a GFCI receptacle elsewhere, sometimes in another bathroom or the garage, and press RESET.
Homes built before these requirements may have little or no GFCI or AFCI protection. Adding it is a common and worthwhile upgrade, especially in bathrooms, kitchens and outdoors. Ask about it during an electrical inspection.
Test them regularly
Manufacturers recommend testing GFCIs monthly. AFCI and GFCI breakers in the panel have their own test buttons; pressing one should trip the breaker, which you then reset like any other. See why breakers trip for the reset method.
If a device will not trip when tested, or will not reset, it needs replacing. Replacement is a job for a licensed electrician.
Keep a simple habit: test the GFCIs when you change your furnace filter or check your smoke alarms. In winter, pay special attention to the outdoor and garage receptacles you use for block heaters and Christmas lights, since moisture and cold are hard on them.
When they trip
- GFCI trips outdoors after rain or a chinook melt. Moisture in a receptacle or cord is the usual cause. Make sure outdoor receptacles have in-use covers, let things dry and reset.
- GFCI trips when one appliance runs. The appliance may have a leakage fault. Try it on another protected receptacle; if it trips there too, the appliance is the problem.
- AFCI trips with a vacuum or old power tool. Worn motor brushes can look like arcing. Try another appliance on the same circuit.
- AFCI trips with nothing running. This can point to a real wiring fault. Leave it off and call.
Some equipment, like a sump pump or a freezer in a garage, is a poor match for nuisance trips because a trip may go unnoticed. Ask your electrician how to protect these loads properly, for example with a dedicated circuit, an alarm or a location where a trip will be noticed quickly. See dedicated circuits.
Never replace a GFCI or AFCI with a standard device to stop nuisance trips. Frequent trips are a symptom. A licensed electrician can find the cause and keep you protected.
Common questions
What is the difference between a GFCI and an AFCI?
A GFCI protects people from shock by detecting current leaking to ground. An AFCI protects against fire by detecting arcing in wiring and cords.
How often should I test my GFCIs?
Monthly is the usual recommendation. Press TEST, confirm power cuts off, then press RESET.
Do I have to add AFCIs to my older home?
Generally, existing wiring is not required to be updated just because the code changed. New or altered circuits may need them. Your electrician will tell you what applies.
Why is my bathroom receptacle dead when no breaker tripped?
It is likely downstream of a tripped GFCI receptacle, sometimes in another room. Find it and press RESET.
Can a GFCI wear out?
Yes. If it will not trip when tested or will not reset, have it replaced.
Codes and permit rules change and every building is different. For work on your system, talk to a licensed electrician and your local permit authority.