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I have an American Standard High Torque Garbage Disposal (QKGO2), and it was installed by the previous homeowner less than two years ago. It hasn't seen too much use, however, because it trips the breaker pretty often. It will run all day with just water, and maybe the occasional tiny scrap, but as soon as there is the tiniest amount of resistance (or even if it's turned on with the sink draining), it will trip the breaker.

It runs, is plugged into an outlet under the sink, and appears to be the only thing on a 20 Amp breaker (we've left it tripped for weeks at a time and have never noticed anything else in the house without power). The breaker is one of those where I have to push it ALL the way to off before I can reset it, if that means anything to anyone.

Does anyone have any suggestions? Thanks!

  • For what it's worth. 1.25 HP works out to about 1000 watts or 8 amps. The disposal might have an additional label on it listing the actual amperage because the HP number is mostly marketing and not a technical specification. I'd be surprised if it's rated to use more than 12 amps or so. – JPhi1618 Feb 1 at 21:16
  • Even if 12 amps is the listing motors under load can draw 3 to 5 times the 12 amp value tripping the 20 amp breaker. – Ed Beal Feb 1 at 22:01
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    But breakers don't trip immediately. They can handle spikes. The thing is, most houses have a disposal on a 20A breaker and it's not an issue. The asker has a problem with a disposal drawing way more power than normal (bad bearings or who knows what) or their breaker is bad. – JPhi1618 Feb 1 at 22:07
  • Product safety codes now require breakers trip to a center position and must be flipped off then on. Related, they will trip even if you are holding them on. – Harper Feb 1 at 23:33
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    @Harper -- UL 489 actually does not require midposition trip (CH's still trip to OFF to this day, and I believe many IEC-style UL489 breakers also are two-position). You are correct, though, that both the UL and IEC specs require trip free behavior – ThreePhaseEel Feb 1 at 23:55
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Something is wrong with the disposal or something is wrong with the circuit breaker. It's normal operation to turn a breaker all the way off before resetting it. I believe that's how all of them work.

To diagnose the problem, you're going to have to measure the power usage of your disposal. You can do this with a "clamp meter" that measures amps or a more consumer friendly meter like a "Kill-a-watt" brand power usage meter.

If the disposal never goes over 20 amps but the breaker is still tripping, the breaker is most likely bad. If it goes over 20 amps then something is wrong with the disposal and replacement is probably the best fix.

  • Motor loads can normally draw 3x to 5x there FLA and be fine. I have seen 1 hp disposals require a 30 amp breaker and this can be done with #12 wiring and be code compliant. – Ed Beal Feb 1 at 21:53
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The problem is a 1-1/2 hp motor. (I used 1.5 As an example because my book only lists 1, 1.5 no 1.25). Motor loads can draw 3 to 5 times under load and there is nothing wrong on a 120v circuit has a book value of 20 amps. So any load on the unit and you trip the circuit breaker. If the wire size is #12 (it should be on a 20 amp circuit) . there is an exception in the code that would allow for a larger breaker the problem is with a book value of 20 amps the correct wire would be larger 125% of 20 amps is 25 so this motor load should have been wired with #10 to be fully code compliant (and hard wired not a plug) code allows for a larger breaker to be used up to 250% but no larger than required to start and run. You may be in luck many motor manufactures base the horse power rating on peak draw (not a true value) if the amperage name plate is 16 amps, the max for a device listed for use on a 20 amp circuit you can upsize the circuit breaker to 30 without having to go to #10 wire but the true full load amperage would need to be below 16 amps to do this per NEC 430.52. And table 430.52. This requires the motor to have overload protection. garbage disposals there is usually a red reset button this is the internal motor overload. The NEC allows motors in these cases to have a larger breaker than the wire size but the wire needs to be 125% of the FLA (full load amperage) to do this. In my jurisdiction it is required to hard wire and for it to be a dedicated circuit it sounds like you have a dedicated circuit, so check the amperage on the name plate as the horse power is probably not true. If there is a listing that states FLA on the motor and it is less than 16 amps you can install a larger breaker. I have had to do this with disposals and AC systems regulary, the disposals usually get looked at to make sure that the wire is sized correctly but they have always passed inspection (note my jurisdiction requires hard wire so something else can not be plugged into this circuit).

  • OP says 1.25HP not 1.5HP. Also, where do you find a table for HP to amps lookup? I was just using online watt to HP calculators and didn't realize there was an official book chart somewhere. – JPhi1618 Feb 1 at 21:42
  • True but 1.25hp is not a listed size that's why I mentioned the HP is probably based on peak power. Table 430.248 covers single phase motors 115v, 230v etc. – Ed Beal Feb 1 at 21:49
  • Interesting, thanks. I have a feeling that table was meant for real 1.5hp motors. When it comes to consumer products, there's no telling what that number really means. I'm sure that disposal came with a 15A plug molded on, just like the 3.5HP shop vacs that they sell at home stores. – JPhi1618 Feb 1 at 21:54
  • I mentioned that vacuums and air compressors are the biggest crooks, from the table you can see the largest motor that could be run on a 20 amp circuit is a 1 hp with a FLA of 16 amps. But as long as the amperage is below 16 a motor load on #12 can legally be upsized to a 30 amp breaker. – Ed Beal Feb 1 at 21:57
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That circuit might have a GFCI on it, either in the breaker or the outlet. If you are certain that there is nothing else on that circuit, you might have a bad breaker.

If you do have a GFCI circuit tripping; That could mean that there is a short in the circuit created by that disposer. It could also be the disposer overloading the circuit. If you are unfamiliar with testing a disposer with a meter, call a qualified electrician.

GFCI

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    Interestingly enough disposals don't require a GFCI outlet, even though it is a great idea to use one. – JPhi1618 Feb 1 at 21:27
  • Well, I looked that up and you are correct. I learned something new today. Thanks! – Jerry_Contrary Feb 1 at 21:37
  • I've seen some arguments that it is within 6' of the sink and is required, but I don't know what most inspectors look for these days. I haven't been in a newly built house for a long time. – JPhi1618 Feb 1 at 21:39
  • The code says within 6' of a sink (not including the kitchen area). I thought that was odd. – Jerry_Contrary Feb 1 at 21:44

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