Can I use a GFI main breaker in series with individual QO AFCI breakers?


Yes, a GFCI sub-panel with AFCI breakers sounds like an excellent way to do that. It avoids the European problem of having the whole house GFCI (RCBO) trip and ruin a refrigerator full of food and freeze pipes (though some European furnaces don't require electricity).

I don't see a problem daisy-chaining since they are different protections. I also like having the arc-fault protection more local than the ground-fault. The GFCI doesn't care, but the AFCI does, because it is literally listening to electrical noise, and it's easier to "hear" when fewer things are talking.

The only thing you need to watch is that your large, full-panel GFCI has the sensitivity that is legally required for bathroom and kitchen circuits. Some of the Euro-style whole-house RCBOs have 20-30ma thresholds, which is not sensitive enough by...

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For all new construction residential dwellings the answer is not too complicated.

For older homes with existing wiring the answer is not as easy. A qualified electrician would need to assess the wiring conditions and even then only by trail and error could they determine if ARC-fault protection would be able to work. In some cases using an ARC-Fault receptacle downstream may be an option, whereas a complete rewire of the existing branch circuit may be needed.

I've elaborated on the answer breaking it up into residential and commerical establishments for educational purposes.

Residential AFCI Requirements

All habitable rooms that contain 120 volt 15 or 20 Amp branch circuits require ARC-fault protection. This includes kitchens, family rooms, dining rooms, living rooms, parlors, libraries, dens, bedrooms, sunrooms, recreation rooms, closets, hallways, laundry areas, or similar rooms or areas.


Residential GFCI Requirements

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Circuit breakers have become the choice of people building homes, unlike the times of yesteryearhad fuse panels. As you may know, circuit breakers and their panels have many different manufacturers and they all look similar, that is, from a distance. But get up close and take a closer look at each of the circuit breaker types and styles and you'll discover that not all circuit breakers are created the same.

In fact, it's just the opposite. Their slot that snaps into the bus bar is different, the mounting attachments are often quite different, and even their physical shape are very different.

To the untrained eye, they may look the same to most consumers, which causes problems when people go out to buy a circuit breaker for a replacement or addition to their electrical panel. Some may choose one based on the price, which is a poor habit to be in when dealing with electrical equipment. Instead, you should always use the same brand and style circuit breaker as is...

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Find the main circuit breaker box. Some homes may have 1 large main breaker box as well as smaller branch breaker boxes.


Locate the defective breaker.

A tripped breaker is halfway between the on and off position.

Before assuming a circuit breaker needs to be replaced, try resetting the breaker by turning off all lights and unplugging all devices on that circuit. Then turn the back to the on position. Some breakers must be turned all the way off before they can be turned back on. Test the circuit breaker by turning on the breaker, and then add the devices 1 at a time. If the light or device becomes operable, then a voltage tester is not needed.


Use a voltage tester to see if power is going out through the wire attached to the breaker.


Turn off the branch breaker boxes, followed by the main power.This should be the large flip switch located above or below all the other smaller ones. It should also be labeled "main" or...
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I was reading a professional article a month or so about AFCI's - there are a number of code jurisdictions that are now holding off on requiring AFCI's, and a few have reversed their requirements for them because they have too much of a tendency to trip without good cause.

Problems I have heard about them include tripping when a microwave tube turns on, stove high-amperage surge when oven or broiler cycles, due to connected surge protector strips trapping power surges, during thunderstorms when the main power line is hit (not necessarily near the house), on hot humid days followed by cool nights (and after thunderstorms and tornadoes when the temperature drops fast) when humidity goes to 100% rapidly due to the cooling causing minor condensation and micro-arcing in house electrical circuits, light switches arcing when turned on or off, brush-type motors in ceiling fans arcing and tripping them out, plugs being plugged into and pulled out of outlets, micro-arcing across dust...

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When Ground Fault Circuit Interrupters (GFCIs) were introduced in the 1970s, similar discussions took place regarding the cost/benefit to the consumer, homebuilder and others. GFCIs have been a standard requirement in homes for over 30 years with additional locations and circuits being added over time as well. GFCI also has a statistical track record over time as to the reduction of electrocutions. On an annualized basis, in 1983, there were almost 900 electrocutions total per year with approximately 400 being consumer product related. Ten years later, the total was reduced to 650 annually and slightly over 200 consumer product electrocutions annually.

With over 20 years of history, statistically based analysis of GFCIs was built on a solid foundation of data. AFCIs are new and have only been installed in new construction on bedroom circuits for a few years. As with all products, given time, they too will be able to provide a solid statistical base of measure.


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If I use GFCI breakers do I still need GFCI receptacles? Also I see some combonation AFCI / GFCI breakers. Are these reliable? And my last question of the weeek. Is the home run in a branch circuit a seperate neutral wire which connects the last receptacle / switch to the neutral bus?

If you use a GFCI breaker, you don't need GFCI receptacles. As long as the breaker provides the level of protection required at the outlet.

Dual Function Circuit Interrupter (DFCI) breakers are reliable.

"Home run" is not a technical term. It may be used to describe a dedicated circuit, where the circuit only supplies a single device. It may also describe branch circuit conductors, that run uninterrupted from the panel to the first device.

April 10, 2015 15:24...

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A tingling sensation just ran up your arm because you tried to unplug your coffee maker from the wall only to receive a shock. You were quite literally shocked since the outlet did not have a GFCI (Ground Fault Circuit Interrupter), or it was not functioning properly. GFCI breaker units detect an imbalance in the electrical current and shut down before that electricity reaches you or blows up the electrical device plugged into the outlet. A single unit monitors several outlets in one section of the house. For example, you may have one breaker for the bedroom and one for the kitchen. When a breaker shuts off, you simply switch it back on. They each have a maximum amperage rating, so first find out how many amps you need for the area. For example, a 20 amp GFCI breaker cannot handle as many outlets or as much power usage as a 50 amp unit can. You can find several kinds on eBay and make your home a safer place for everyone.

Shop the large inventory of electrical and test...

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Possibly arcane question about my computer and AFCI circuit breakers.

I moved not all that long ago into a brand new condo (new construction, that is) and as per code the bedrooms all have AFCI circuit breakers on the outlets rather than GFI breakers. Sounded fine to me. Except that since I live alone I'm trying to set up one of the "bedrooms" as an office/den/whatever which, of course, requires my computer be in there. The problem is that the computer, with insane high end video card and so forth, confuses the AFCI circuit breaker and nuisance trips every single time I try to plug in the computer. Every. Single. Time.

I can plug an HDTV, XBOX 360, DVD player, satellite TV receiver, DSL+router, monitor, printer, and telephone in to a power strip and one of the outlets in here with no problem whatsoever. But if I unplug all of that crap and plug in my computer - by itself, no peripherals, etc - the AFCI breaker trips instantly. I can use the computer perfectly well...

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Know what you're getting into

An inside look at your main panel

Your main panel might not be exactly like the one here. With any panel, find the large cables and the lugs they're connected to. They're the parts that are always live, even when the main breakers are switched off

Yours might look like this

The photo shows a different configuration where the large cables and lugs are located on the right-hand side of the circuit breaker box, rather than at the center.

We believe in safe DIY. That's why we've always been reluctant to show readers how to open a breaker box and connect a new circuit. Even with the power shut off, there's a chance you could touch the wrong parts and kill yourself. But then we figured if we didn't show you, you'd just go search the Internet. And that scared us even more. So we're going to walk you through the process, showing you the safest way to open the breaker box, wire a new breaker and test your...

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They work differently.

A GFCI breaker trips when it senses an overload, and prevents you from becoming part of the circuit.

AFCI stands for Arc-Fault Circuit Interrupt, and they are designed to stop electrical arcing. For example, lets say you've got an appliance, fixture, etc, with a bad contact, or a broken wire. The electricity may arc across that bad connection intermittently, and while not overloading a GFCI (until its too late), it will produce heat at the arc... this could result in a fire. In the case of an arc, like this, the damage could already be done, by the time a GFCI trips.

Here is a good article on the difference -

And this one goes into more detail, from the National Electric Manufacturers Association -


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I have a problem I am hoping someone can help with.

The problem … Outlets and switches don’t work. I have a GFCI circuit breaker in the garage/at the panel. It tripped and won’t reset. I got it to reset once but then I flip the light switch and it immediately trips.

I bought a new GFCI breaker and installed it, same thing. At this point I assume it is not a faulty breaker but a problem.

The breaker runs on it two unused bedrooms (lights and outlets), the lights in an unused bathroom (but not the outlets) and one outlet in a hall (on the other side of the wall from the unused bathroom mentioned).

How the problem happened…I went to the room one day, turned on the light – it worked. A few hours later I went back to the room (to put back what I took out) and the light didn’t’ work. During those few hours we didn’t use any of the lights or outlets on that breaker.

What I have done….*Replaced the GFCI breaker, *Went through the house...

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Photo © david.asch -

Arc-Fault Circuit-Interrupters were the new kid on the block when they first appeared in the 1999 National Electrical Code (NEC). Since then, we have seen the technology advance to a new generation of devices, along with incremental expansion of the requirements for AFCIs in each new code edition. The next (2014) edition will continue that trend.

Why AFCIs?

An arc results from an electrical current propagated through air. A common example of the discharge of electricity between electrodes is the spark plug in a car engine. Snap switches sometimes will cause an arc as the contacts make or break continuity, although arcs are momentary and rarely damaging. A sustained arc can occur at a loose connection or between conductors that have damaged insulation. These electrical arcs can produce temperatures of several thousand degrees while still drawing less current than is necessary to trip a conventional breaker...

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I have a newly wired studio with a new 125A Square D service entrance panel. 6 individual circuits are wired with 20A breakers for some large draw equipment. Trouble is the 20A breakers keep tripping... A lot. They never used to at all.

This issue seems to be specific to my new place and these Square D breakers.

I had the same set-up in the previous studio ( built in 1993) which worked perfectly. Typically this equipment works fine on standard 15A circuits (outside the studio, which we regularly do). Occasionally 15A breakers will trip so in the previous studio we installed the 20A breakers on dedicated circuits and eliminated tripping.

Now, the exact equipment on the new Square D panel is constantly tripping the 20A breakers. Curious?

When I take the equipment anywhere outside the studio it works fine (downtown offices, my 3 year old new home, even an older unit in my condo, etc) .

My equipment is about 15 years old and in very good condition....

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