1.25 HP Garbage Disposal Blows Fuse

Question

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!

Answer 1

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.

Answer 2

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).

Answer 3

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.