Can a dishwasher and garbage disposal share a circuit? What is a "Amp Draw" and what does it tell us?
Is it possible to put a dishwasher and garbage disposal on the same circuit and operate under the 80 percent rule?
Wow!A 75hp disposal.I hope that's not true.It's done everyday.Home disposals are usually 1/3 or 1/2 horsepower and draw no more than 8 Amps.Commercial disposers are more powerful.
Installation of 1-30 Amp circuit for both.The load when the heating cycle is on would be 12 Amps the D/W draws.Not the motor.The small motor in a D/W doesn't draw much.For about a second or two on start up, I'm thinking 4-5 Amp running and probably no more than 6.Larger motors have a noticeable jump on start up and draw more water.The NEC requires individual circuits for safety reasons.Most of the time Electricians and repairmen don't turn off power to all circuits in a junction box.This has resulted in injuries and death as a result of the NEC requiring individual circuits.You can get 2 circuits in one full sized space with one of the type breakers."piggy back" is for Square D.For G.E.They are tandem or wafer.If you get a "quad" breaker, Square D, do not try to force one brand of breaker into another brand.It might function, but it would void the listing and be a Code violation.If using 2 circuits on the same phase, do not use one run of 12-3 romex or MC.Keep the neutrals separate by running 2 sets of 12/2.If the grounds end in a junction box, tie them together.Hard wire the D/W.There is a possibility that occurs to me.You can run one 20 Amp (12-2) to a 3 position switch.On-Off-On.Remove the tab between the two hot screws from the 2 switch legs.If there was a short or overload at either appliance, you could not run both at the same time.The switch is more expensive than the breaker.I would change the breakers and run 2 new circuits per code.In the future, I wouldn't have to worry about a Home Inspector flagging the work for a potential buyer to see, and me repairing it.Good luck.
Can it work?When you turn on the garbage disposal, the dishwasher isn't in it's heating cycle.Many of the dishwashers have a heating element for drying the dishes.
If you were doing a new electrical installation, current code requires a separate, dedicated 15 Amp circuit for each device, but lots and lots of people are living comfortably with the situation you've described.
A 30 Amp circuit is not a good idea.The appliance cords aren't rated to be plugged into that much power.If a problem occurs within the device which causes an unusual power draw, the cord could burn up before the circuit breaker blows.It would violate present codes.
I have never seen a home that was wired like this, they both share the same circuit, but they are not directly connected, and the ability to install an on/off switch for the disposal is not interrupted.
They should be dedicated circuits.The garbage disposal has overcurrent protection circuits in it, that's why it has a high starting surge current.The breaker will pop even if it's only taking up 8 Amps at the time.
You need the data in order to make a decision.It is common for the heating element in the dishwasher to be over 10 Amps, while the disposal pulls 3-4 A.
Table 21.21B2 states clearly that if the recep is fed from a single circuit, the load under the sink will not exceed 12A.It's hard to believe that most people use a 20A rated recep when they are trimming on the cheap and using a single circuit under the sink.
Absolutely they can.It's rare to run them at the same time.The disposers are 1/3 HP and the dishwasher rarely runs more than 4 Amps.