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Joined: Mar 2005
Posts: 240
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i want to know if anybody can help me calculate if i can put a 1/2 HP disposer motor and a dishwasher that draws a nameplate or 9.1 amps on a 20 amp circuit.
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Joined: Jul 2004
Posts: 10,006 Likes: 37
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Nominal FLA on a 1/2 HP motor is 9.8a (plus 25%) added to 9.1a seems to be too much for a multiple motor load.
If you are cord and plug connected they each do represent less than 50% of circuit ampacity so it might be "hold your nose" legal. I have seen this go both ways but the preferable solution is a multiwire circuit with 2 phases feeding the duplex.
Greg Fretwell
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Joined: Mar 2005
Posts: 240
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thanks gf i just wondered if possible...
could you elaborate on the 50% since cord connected dishwashers are feasible and do provide disconnecting means for motor.
h2o
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Joined: Jul 2004
Posts: 10,006 Likes: 37
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It all gets down to how you read
210.23(A)(2) Utilization Equipment Fastened in Place. The total rating of utilization equipment fastened in place, other than luminaires (lighting fixtures), shall not exceed 50 percent of the branch-circuit ampere rating where lighting units, cord-and-plug-connected utilization equipment not fastened in place, or both, are also supplied.
Most inspectors would say all fixed in place equipment must be less than 50% but I have seen this stretched to say any one piece can't exceed 50%, particularly on an intermittant load like a disposal.
Vote me for "all".
Greg Fretwell
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Joined: Jan 2005
Posts: 5,476 Likes: 3
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One caution here....look at the FLA on the disposal, and not the "horsepower" rating. I have seen a lot of inflated "horsepower ratings" over the years.
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Joined: Feb 2005
Posts: 693
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"...lighting units (or) cord-and-plug-connected utilization equipment not fastened in place..."
Neither describe either a dishwasher or a disposer, so 210.23(A)(2) doesn't apply.
I routinely place both of these on a 20-amp circuit. A disposer is probably the epitome of an intermittent load.
Larry Fine
Fine Electric Co.
fineelectricco.com
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Joined: Apr 2005
Posts: 73
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Good subject. I have been told that they make a 3 way switch that can be used in these applications. One position for dishwasher and other for disposal. Now having said that I personally have not seen one. Do they make them?
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Joined: Oct 2004
Posts: 135
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Any 3-way rated for the load would work.
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Joined: Aug 2003
Posts: 1,374
Moderator
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I am moving this to the NEC section.
Ryan Jackson,
Salt Lake City
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CDS
Nicholson Ga
Posts: 34
Joined: June 2006
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