GFCI Vs AFCI (EE Questions)

1.) Which would be better to use for breakers, GFCI or AFCI? My breaker box has what I guess are standard breakers, they trip if lets say, I use a toaster and microwave on the same circuit like an idiot but are otherwise in good shape but are about 30 years old. I want to get work done and replace them to minimize shock risk. 2.)
I already have new receptacles in the kitchen and bath that are GFCI, would those outlets conflict with a GFCI breaker somehow?
3.) Would a ground fault or arc fault on something plugged into a surge strip (well-maintained) trigger the breakers?

4.(not quite a question) Thank you for all replied for my unease about a plug sticking halfway out of the outlet, I’m like 90% over my fear that it would cause a fire, and I sleep easier, the above questions are related as to how I want to prevent risk of electrocution now. Using this forum is the only thing that keeps my anxiety at ease, so I apologize in advance if some questions seem silly.


If you had to choose between the two, GFCIs are the way to go. IMHO, the likelihood of getting electrocuted by a ground fault is higher than that of burning your house down due to a loose connection.

But, why not go all the way and get both.

Do you want to protect against being shocked? Or do you want to protect against your house burning down?

The purpose of GFCI is to protect against being shocked. Because getting shock can lead to death.

The purpose of AFCI is to protect against smoke & fire caused caused by arcing. Because smoke & fire can lead to death.

GFCIs protect against ground faults, i.e. where current finds an alternate way back to ground (often through you). Ground faults are a particular risk whenever there is water present, which is why you already have them in your kitchen and bathroom. Current code also requires them in unfinished basements, near wet bars, and in laundry rooms, which are all code changes that were made after your house was wired up.

While water is a particular risk for ground faults, you don’t necessarily need water nearby to get this type of shock. I got the crap shocked out of me when I was a teenager by playing an electric guitar through an ungrounded amplifier, and I went to open a screen window in a house with aluminum siding. Musicians have been killed by improperly grounded amplifiers.

AFCIs protect against arcing, and were created in response to people being killed by fires caused by frayed extension cords or similar faults. Initially, these were required only for bedrooms. Current code requires them in bedrooms, living rooms, dining rooms, kitchens, rec rooms, hallways, closets, pretty much everywhere there’s people.

There are about 50,000 fires caused by electrical faults per year, with an average of about 500 deaths. The vast majority of those are caused by an arc fault. Somewhere around 50 or 60 people are killed per year by electrocution.

I would say use AFCI breakers, and add GFCI outlets to your laundry area and any other areas that are required by current code.

I realized after submitting that this question wasn’t clearly answered.

A GFCI measures the current going through the hot and the neutral. If they don’t match (within 5 mA) the GFCI assumes there’s a ground fault and trips. It doesn’t matter if there’s a power strip involved. It really doesn’t matter what is attached to the circuit. The GFCI just makes sure that all of the current going out through one wire comes back through the other. If they match, there’s no possible ground fault.

Similarly, an AFCI works by looking for the electrical pattern caused by arcing. Again, it doesn’t matter if there’s a power strip or anything else on the circuit. If the AFCI detects the pattern of an arc fault, it trips.

I think I’m going to go with the combination Siemens AFCI/GFCI breakers. Couple months at most, I’d rather install them all in one go. Thanks again! this forum never ceases to amaze me.

Sorry for the hijack, but I am curious on where most arcs originate.

I have always been under the impression, perhaps wrongly, that most electrical arcs occur at 120 VAC receptacles. There are two ways arcing can occur at a receptacle: 1) a loose connection where one of the (12 AWG or 14 AWG) wires terminates into the back of the receptacle, and 2) a loose connection where one of the prongs on the plug mates with the spring contact inside the receptacle. In either case it would be classified as a series arc fault, and would only occur when there is a load.

And then there are parallel arc faults. These can occur with or without a load. I believe they are more rare but (obviously) they’re much more energetic. I also believe your example of a frayed cord would lead to a parallel arc fault.

Finally, I once heard AFCI are pretty good at detecting parallel arc faults, which are rare. But when it comes to series arc faults - which I believe are much more common - I have heard most AFCI breakers either can’t detect them or do a poor job of detecting them.

A lot of the literature I’ve read mentions extension cords specifically, but I didn’t know the actual statistics so I had to dig those up.

In the 1980s, the Consumer Product Safety Commission paid the United States Fire Administration to conduct a detailed study regarding the root cause of electrical fires. Their report found that electrical fires occurred most often in branch circuit wiring, followed by receptacle outlets and extension cords.

Siemens has a good history of AFCIs here (warning, pdf):

Older AFCIs were much better at detecting parallel faults than series faults. I know they’ve made a lot of improvements to the technology in the last 5 to 10 years or so, and the newer ones are supposed to be pretty good at detecting either type of fault. I don’t have any actual statistics about it, though.