I live in a home that was built in 2018. Having lived here since 2022 I would not expect that I'd need to perform much upkeep on this home, but nevertheless because there are so many moving parts to a home there are at least some parts that need replacing anyways. Some things are more frustrating, expensive, and require more expertise to replace than others. One repair which came up recently within my home was quite small and easy to do and I think more could benefit from knowing at least how it's done, if not to do it yourself then to know how to approach hiring someone to do it.
Problem
One day I open the door to my master bedroom and notice the light on the overhead fan is off even though the light switch for the overhead fan is on. I toggle the light switch a few times; nothing happens. Toggling the immediately adjacent fan switch does nothing, also, and the fan remains off no matter how many times I throw it. The lights and fans in the master bath, adjacent to the master bedroom, do not work either.
This is a problem. I'd rather be able to use the lights and fans rather than for them to exist for just decoration. At this moment I believe (and was correct in believing) that the lights and fans and outlets in both rooms are connected to the same breaker in the breaker panel.
Background
If you don't know, outlets and fans and lights and stuff are routed through a building's breaker panel which is responsible for distributing and regulating the current delivered to all outlets on every breaker's circuit. There are many individual breakers in a breaker box. With the cover off, mine looks like this:
To analyze this box, starting from the bottom, there are two very thick cables, one red and one black, coming through an inlet at the bottom of the box. These cables are the exclusive conduits for power to my home. They are fed into a 200A breaker visible in the image. Both these cables carry alternating current (AC) power signals. They are 180° out of phase, such that when one phase is at its peak positive voltage (120v) the other is at its peak negative voltage (-120v). By their powers combined they can provide an appliance with 240v. If you connected these lines to an oscilloscope you'd see that the signal on these wires does not really peak at 120v but at 170v but this is very beside the point unless you care what the difference between measuring RMS and peak voltage is. In any case, no matter how you measure it, these wires transmit power to my home from the street.
The power company ensures these cables have a nominal 240v RMS voltage across them. This is the standard RMS voltage in all 50 US states, US territories, some Central American countries and some regions of Japan. The frequency across these places may differ but that's not important right now.
In addition to these two cables there is a single neutral cable, provided by the power company, tapped from the center of the same upstream transformer which provides the 240v. Relative to the cables carrying AC power this neutral wire is a constant 0v so any appliance provided with neutral wire and any one of the power wires will see a 120v RMS signal.
Anyway, none of this happens in the home. It all happens at a transformer somewhere within my neighborhood, and each transformer in the neighborhood feeds a few houses. I think these are the small green boxes I see every couple houses here. Inside my breaker box I only get three wires: the two thick power lines and a neutral. The neutral is likely grounded to the Earth with a grounding rod very nearby. Older homes have metal plumbing so the ground can be short to Earth via the home plumbing itself.
In the breaker box picture, coming out of the top of the 200A breaker are two metal bus bars that are sort of gold colored which feed a series of 15A to 20A breakers. These breakers feed the rooms and appliances in my home. Many rooms are fed from one breaker, but if at any point appliances on any breaker exceed the breaker's rated amperage the breaker will trip and cut power to the rooms on the breaker completely. This is a safety thing provided by breakers to prevent house fires. Previously this guarantee was provided by fusesqbut fuses are little strips of metal that burn up when amperage exceeds the fuse rating and fuses were a pain in the ass to replace so everyone uses electromechanical breakers now. You can toggle them on or off by throwing a physical switch, which toggles whether power is delivered to the circuit from the bus through the breaker.
As you may be aware, there is electrical code which enforces safety measures for outlets in bathrooms, kitchens and sometimes bedrooms because of increased risk of ground faults due to the presence of water. That's because running just 0.01A ~ 0.02A through you can cause muscles to contract and can make it hard for you to let go of a live wire! Even small current running directly through your heart can kill you too; as little as 10μA can cause fibrilation. But don't worry because anything under 200v will probably just travel along your skin, never contract your muscles and you'll probably reflexively flinch back and probably not die. But better safe than sorry! That's the reason for safety devices like GFCI (Ground Fault Circuit Interrupters) which is the particular device installed in bathrooms and kitchens to cut power much earlier than the 15A breaker itself.
A GFCI breaker will typically trip if there is a difference in current of at most 6mA between the hot wire and the neutral return wire because the presence of a current differential means current is finding some other path to ground on that circuit, possibly through you! A GFCI breaker, at least the one I have installed in the panel, will also trip on overcurrent.
Solution
Throwing the breaker back to the "on" position turned the lights back on for a day. Then the breaker tripped again. Again I threw it back and it stayed on for another day until tripping. We went back and forth for a few days until I decided the breaker was in need of replacing. There is additionally a little status light on this breaker that flashes when it trips and sometimes it would flash 6 times, indicating a self-test failure.
Replacing it did the trick. I went out and bought one on the assumption that mine was bad and, sure enough, replacing it stopped the intermittent tripping. These are the tools I needed:
- Phillips head screwdriver or bit (panel screws)
- Square (Robertson) S2 screwdriver or bit (breaker and bus bar screws)
- Correct breaker
In the US a lot of electrical work requires a square screwdriver. I have no idea why this is the case. Evidently Canada uses square drivers for a lot more stuff than the US does, probably because they are strictly better screws and were invented by a Canadian.
In addition to not having the correct screwdriver before I began, I bought the wrong breaker twice. Third time was the charm. So you can avoid what I did and learn, I bought these breakers, in order:
- Non-GFCI 15A breaker (fits but not GFCI/AFCI)
- 15A GFCI/AFCI Square-D breaker GFTCB115CS (doesn't fit in my panel)
- 15A GFCI/AFCI Cutler-Hammer breaker CH115GF (correct!)
My first mistake was not realizing that GFCI/AFCI breakers exist. I thought that was only technology that existed at the outlet in the form of "test" buttons but no, GFCI/AFCI can live on the breaker too. GFCI breakers eliminate the need for individual protection at the outlet.
Secondly, my panel is made by Eaton Corporation which makes breakers for both Square D panels (Eaton calls these UL-Classified) and Cutler-Hammer panels, a brand which Eaton acquired. Mistakenly, I bought the GFCI/AFCI Square-D breaker before learning this.
Finally, I bought the correct breaker, a 15A cutler-hammer GFCI/AFCI breaker, part number CH115GF.
To replace the breaker, throw the main breaker (in my case, the 200A one) and remove the breaker panel. Mine had six screws along the edges. Throwing the big breaker will deenergize everything above it (remember the main breaker itself is still is energized from the power company so do not touch it!) and with this out of the way you can freely work on the breaker with less risk of getting zapped.
With that breaker thrown you can safely rock the troublesome smaller breaker (in this case the 15A one I am replacing) off the bus by pressing on the end which is furthest from the center of the panel, at least for Cutler-Hammer breakers, because Cutler-Hammer breakers have a hook on the bottom which hooks onto a metal piece on the bus bar and secures it in place.
With the breaker only attached by the wires, loosen the screws holding the hot and return wires in place with a square screwdriver bit (S2). Then, trace the breaker's pigtail connection to the neutral bus bar, loosen this screw, and fully remove the breaker. Pop in the new breaker, connecting the hot, return and pigtail wires in the same configuration as before you removed the old breaker. Ensure the wires are held securely and the breaker and neutral bus screws are sufficiently tight such that the wires will not just pop out.
Eazy enough!