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Joined: Jun 2004
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Can a dishwasher with a nameplate amp rating of 8.7 amps and a disposal with an amp rating of 6.7 amps be connected to the same 20 amp branch circuit?
shortcircuit
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Joined: Jan 2005
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And why would that be a problem? I don't see anything near 20 amps on the circuit ,,,, even if you assumed continuous operation!
[This message has been edited by renosteinke (edited 03-07-2007).]
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Joined: Jun 2005
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Depends on the manufacturer specifications. I'd check those first. As long as there is no lighting load on the circuit, I say you're good to go!
422.10 (B) 210.23 (A)(2)
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Joined: Mar 2005
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Disposals are on for such a short amount of time, they're unliky to ever trip a breaker, irregardless of whatever else is on the circuit- you could already have a 22A overload on that 20A circuit and still never trip it with a disposal.
In your case, I certainly don't see a problem sharing a dishwasher and disposal. In my house, I have the microwave sharing the circuit, too- the duty cycles are so short with so little simultaneity, it's just not a problem. (It wasn't completely intentional or I would have used two circuits... I simply forgot the dishwasher until it was too late to add a new circuit!)
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Check for a local amendment. I've seen cities require separate circuits for the DW and disposal.
steve
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Why would they do that, stamcon?
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Joined: Jun 2004
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Thank you for the replies...
I have always installed a seperate circuit for each appliance, but do not remember why I had been taught to or if it was a code requirement.
I found 430.53(A)which seems to apply?
shortcircuit
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430.53 (A) will not help you here because both of your motors are over 1 horsepower. And 430.53 (A)(1) specifically does not allow motors over 6 amps.
1 HP = 746 watts
6.7 amps x 120 volts of alternating current = 804 watts 8.7 amps x 120 volts of alternating current = 1044 watts
Hope that helps you.
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dishwashers also have a heating element; they are not a strictly motor load
Earl
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Shock, don't let that 746w per horsepower thing confuse you. That is a theoretical number. You have to use the nameplate rating or 430.148. I doubt the dishwasher has more than 1/4hp motor in it and I bet it is smaller. The 8.7a reflects the 1kw heating element and the timer. The disposal is probably 1/2hp, maybe 3/4. I agree 430.(A)(1) seems to prohibit it but that conflicts with 210.23(A)(2). I also agree with Steve that this will probably never cause a problem and it is not a danger to the 12ga conductors but the AHJ will have to agree with that too. The more I read the more confused I get. Simply the wording of the first sentence of 430.53(A) is contradictory. "Several motors, each not exceeding 1 hp in rating, shall be permitted on a nominal 120-volt branch circuit protected at not over 20 amperes", but a 3/4hp motor is 7.6a.
Greg Fretwell
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