John1000
Member
- Location
- Baltimore, MD
- Occupation
- master electrician
Hello. First time poster. Engineering school dropout. Licensed master electrician since 2012. Well aware of how AFCIs work-- or so I thought.
So,...Recently did my own MPU and, although my AHJ does not yet require AFCI, I wanted everything to be "perfect", so I did it all as if building a new home in 2022.
QO 200 amp 54-space panel with plug-on neutral, about 44 spaces used. Basically, all circuits except maybe the gas hot water furnace are protected by either a DF or AF breaker as applicable. The salesman at my supply house tipped me off to the imminent introduction of revised DF breakers which are shorter, have a gray handle and LED indicator which blinks following reset to indicate the type of fault which occurred. He said these new DF breakers have revised sensing to prevent nuisance tripping of VFDs in treadmills, etc. He said only the DF version benefitted from the improved sensing, so advised not to special order the AF ones. (Not sure if this is true, though.) So, about half the panel has these fancy new DF breakers. All the AFCIs are the familiar long ones we've seen for about 20 years, but in plug-on. This has all worked without error for nearly a year.
In January, I decided to buy a tabletop hot water dispenser machine to allow making tea, instant coffee, etc. without tying up or waiting for the microwave. It is called an Aqua Optima. It's basically an on-demand tea kettle with a reservoir, sort of like a Keurig without a pod holder. It has worked flawlessly for about 6 months. However, lately it has been tripping the breaker. I swapped the AFCI breaker as well as the GFCI receptacle. Still tripped immediately. Then I swapped the receptacle to 20 amp version. The 15-amp version says "20 amp feedthru", so assuming the trip contacts are identical, but have not cut one open to see. I have a Flir and noticed the romex conductors light up to 89 deg. F, which is well under 75 deg. C (or 167 deg. F). Other 12 gauge wires in the basement ceiling display similar or higher operating temperatures, so I think this is ok. Highest temperature in the panel is 126 deg. F from all the 3/4" breakers with their electronics crammed together. The appliance does use 1500 watts, making it likely the highest 120 volt cord and plug load in the house. It has been 90+ deg. F lately, so I would suspect simple thermal trip. But this is unacceptable on an 80% (or <16 amp) load and the basement is closer to 75 deg. F. Another phenomena I have noticed is that other AFCI breakers trip randomly. As I understand it, this indicates an unstable current signature being conducted by the appliance which is bleeding into the sensing of other breakers on the same phase. I also have a portable oscilloscope and have put a 30 amp CT on the load. It's a perfect sine, but with faint teeth on the sine. On concerning thing I notice, though, is that the modulation of the heating element cycling on/off to maintain temperature does not switch at zero crossings. It just clicks on and off at random points in the waveform.
I know I am diving WAY into this, but it is in my nature to not stop until I find a solution. I have also read that Keurigs and some tea kettles do the same thing. Has anyone found a solution to such behavior?
My next step, I think, may be to swap the affected breaker to the QO120PAF, which is the fancy revised version. This would at least indicate type of trip sensed. Nowadays, of course, if I go this far, might as well swap all the countertop recepts. to unprotected, place labels on the faceplates and swap their breakers to the purple button QO120PAFGF,...but this would be a touch insane and I just think it "looks right" to have GFCIs clearly present on a kitchen countertop. It clearly indicates with a bright green light that the outlet is hot and puts the user's mind at ease being able to hit the test/ reset buttons without going down to the basement IMHO. Also, I suspect there was nothing wrong with the 15 amp GFCI which was there for years before anyway, though technically, 1500 watts is out of spec for an 80% loading.
I think the KISS answer is the appliance may be creating noise. Lots of reports of Keurigs doing this, and I think I recall something in the advertising saying the Aqua Optima uses the same control electronics. Considering maybe a ferrite choke to filter noise, maybe? To get super nerdy about it, I'm considering buying a zero crossing solid state relay and re-wiring the thermostat device to control the relay rather than randomly cutting the waveform. Actually a little excited to try this approach.
Thanks for any direction on this.
So,...Recently did my own MPU and, although my AHJ does not yet require AFCI, I wanted everything to be "perfect", so I did it all as if building a new home in 2022.
QO 200 amp 54-space panel with plug-on neutral, about 44 spaces used. Basically, all circuits except maybe the gas hot water furnace are protected by either a DF or AF breaker as applicable. The salesman at my supply house tipped me off to the imminent introduction of revised DF breakers which are shorter, have a gray handle and LED indicator which blinks following reset to indicate the type of fault which occurred. He said these new DF breakers have revised sensing to prevent nuisance tripping of VFDs in treadmills, etc. He said only the DF version benefitted from the improved sensing, so advised not to special order the AF ones. (Not sure if this is true, though.) So, about half the panel has these fancy new DF breakers. All the AFCIs are the familiar long ones we've seen for about 20 years, but in plug-on. This has all worked without error for nearly a year.
In January, I decided to buy a tabletop hot water dispenser machine to allow making tea, instant coffee, etc. without tying up or waiting for the microwave. It is called an Aqua Optima. It's basically an on-demand tea kettle with a reservoir, sort of like a Keurig without a pod holder. It has worked flawlessly for about 6 months. However, lately it has been tripping the breaker. I swapped the AFCI breaker as well as the GFCI receptacle. Still tripped immediately. Then I swapped the receptacle to 20 amp version. The 15-amp version says "20 amp feedthru", so assuming the trip contacts are identical, but have not cut one open to see. I have a Flir and noticed the romex conductors light up to 89 deg. F, which is well under 75 deg. C (or 167 deg. F). Other 12 gauge wires in the basement ceiling display similar or higher operating temperatures, so I think this is ok. Highest temperature in the panel is 126 deg. F from all the 3/4" breakers with their electronics crammed together. The appliance does use 1500 watts, making it likely the highest 120 volt cord and plug load in the house. It has been 90+ deg. F lately, so I would suspect simple thermal trip. But this is unacceptable on an 80% (or <16 amp) load and the basement is closer to 75 deg. F. Another phenomena I have noticed is that other AFCI breakers trip randomly. As I understand it, this indicates an unstable current signature being conducted by the appliance which is bleeding into the sensing of other breakers on the same phase. I also have a portable oscilloscope and have put a 30 amp CT on the load. It's a perfect sine, but with faint teeth on the sine. On concerning thing I notice, though, is that the modulation of the heating element cycling on/off to maintain temperature does not switch at zero crossings. It just clicks on and off at random points in the waveform.
I know I am diving WAY into this, but it is in my nature to not stop until I find a solution. I have also read that Keurigs and some tea kettles do the same thing. Has anyone found a solution to such behavior?
My next step, I think, may be to swap the affected breaker to the QO120PAF, which is the fancy revised version. This would at least indicate type of trip sensed. Nowadays, of course, if I go this far, might as well swap all the countertop recepts. to unprotected, place labels on the faceplates and swap their breakers to the purple button QO120PAFGF,...but this would be a touch insane and I just think it "looks right" to have GFCIs clearly present on a kitchen countertop. It clearly indicates with a bright green light that the outlet is hot and puts the user's mind at ease being able to hit the test/ reset buttons without going down to the basement IMHO. Also, I suspect there was nothing wrong with the 15 amp GFCI which was there for years before anyway, though technically, 1500 watts is out of spec for an 80% loading.
I think the KISS answer is the appliance may be creating noise. Lots of reports of Keurigs doing this, and I think I recall something in the advertising saying the Aqua Optima uses the same control electronics. Considering maybe a ferrite choke to filter noise, maybe? To get super nerdy about it, I'm considering buying a zero crossing solid state relay and re-wiring the thermostat device to control the relay rather than randomly cutting the waveform. Actually a little excited to try this approach.
Thanks for any direction on this.
