Countertop insta-hot AFCI rabbithole

[John1000]

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.

 

[Little Bill]

Put in a regular breaker and a GFCI receptacle, done!

 

[ActionDave]

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.

How many cups of coffee have you had in the last twenty four hours?

 

[retirede]

How many cups of coffee have you had in the last twenty four hours?

 

[electrofelon]

.....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.

Well as you can see you made a big mistake. I would never ever use AFCI's if not required. They are banned on my property in fact. I would cut your losses and throw them all in the garbage. Actually if you can find an empty dumpster, the sound of them hitting the metal bottom is very satisfying. Or if you can dig up an address, send them to one of the members on that CMP that voted for them.

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.

If a load is not continuous (three hours or more). You can load the circuit to 100%. There is not general "80% loading" rule.

 

[ptonsparky]

Have checked the heating element for a ground fault? That does happen.

 

[ptonsparky]

I've made pigtails to check the EG current on items in the past. I made sure the current was within the limits of my Fluke 87, then put it in series. 10 amp scale, then milliamp.

 

[suemarkp]

If a load is not continuous (three hours or more). You can load the circuit to 100%. There is not general "80% loading" rule.

There is in 210.23(A)(1) - on multioutlet circuits, no one cord connected item can exceed 80% of the circuit rating. I don't know how anyone would enforce this other than to require an individual branch circuit in the instructions which no one will read. That is one reason why I like multioutlet branch circuits to be 20A instead of 15A. It does seem 1500 watts is right at the 80% limit if you use 125V as your baseline voltage though.

 

[John1000]

Thanks for all the suggestions. It has really helped me rack my brain and go down some different roads of thought. I think I may have figured it out! [fingers crossed]. The tripping seemed to be correlated to ambient temperature, but I have trouble believing the breaker itself could get so far out of spec that it would trip like that since the environment of the main panel bus in the basement is a relative constant. I have seen breakers thermal nuisance trip when installed outside on a southern exposure with panel door open and sun hitting them. But this is a basement. Pretty much 75 deg. F year-round. The environment of the receptacle, however, is that of a poorly insulated outside wall in nearly 100 degree heat at mid-day. Mid-day is when the worst behavior would occur. Also, at times the behavior was so pronounced that other breakers across the panel would trip, and I did not see ridiculously unusual behavior when I clamp an oscilloscope towards the end of the day when I came home. So, I pulled out the Leviton "20 amp" GFCI receptacle, took it apart and popped it apart on a vice. The contact terminals showed evidence of mild arcing! Brand new receptacle purchased yesterday and I know for a fact it was tested and reset twice before plugging anything in, but not once was it operated under load. I'm thinking something in the draw of the boiler was either simply too hard of an inrush for the GFCI relay or else some mystery frequency like some kind of harmonic resonated in a way which caused it to chatter. The machine does make a high pitched singing type noise as it dispenses, so who knows unless I take that apart as well.

I went a little crazy and did swap the receptacle to a standard 20 amp decora, swapped the breaker to the fancy dancy gray-handle dual function QO120PAFGF and took a label maker and marked the type of protection and breaker location on the wall plate. Also saved the instructions in case it does trip and I need to decode the blink pattern. However, so far so good. Tested multiple runs of 8 ounces of boiling water and also in conjunction with the slightly lower wattage Nespresso on an adjacent breaker and so far the ambient temp and other conditions have been about the same. No trips. We shall see, but I think I got it!

This might explain why other 1500 watt devices such as certain Kuerigs, tea kettles and hair dryers pop AFCI-- the GFCI receptacle could very well be chattering? If this success continues another couple days, I think perhaps that's the differential diagnosis and I might write to Leviton.

 

[John1000]

I've made pigtails to check the EG current on items in the past. I made sure the current was within the limits of my Fluke 87, then put it in series. 10 amp scale, then milliamp.

Never popped the GFCI, though, and this was actually a fresh romex of only about 15 feet. All formerly multiwire countertop circuits were ripped out and re-fished to either individual 12/2 or 12/2-2 in preparation for the AFCIs.

 

[tortuga]

I pulled out the Leviton "20 amp" GFCI receptacle, took it apart and popped it apart on a vice. The contact terminals showed evidence of mild arcing! Brand new receptacle purchased yesterday and I know for a fact it was tested and reset twice before plugging anything in, but not once was it operated under load.

That is interesting, I have run into this also.
Welcome to the forum we'll have lots more AFCI threads for you you to chime in on so stay tuned.
Now put the other breaker back in just for fun (no gfci) and see if it trips.

 

[Bill_F]

Excellent overview!

 

[qcroanoke]

I would have done what post#2 and post#5 suggested.