Dishwasher on it's own circuit, correct?

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  #1  
Old 03-15-05, 09:35 AM
JeffNemo
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Dishwasher on it's own circuit, correct?

I'm removing a cabinet in my 1940's bungalow and installing a dishwasher. This must be plugged in behind the dishwasher (not under the sink) and on its' own circuit, correct? I'd love to plug it in with the disposal, but my understanding is that the local codes don't care for that any more.
 
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Old 03-15-05, 09:49 AM
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The dishwasher does not need to be on it's own circuit. It can be on the same circuit as the disposal. It can be on many other circuits also. However, it will draw power, especially if it has a built in temperature booster to boost the hot water temperature. For this reason, it is a good idea to have it on it's own circuit, or at least on a circuit that gets little use.

It cannot plug in under the sink, the plug must be behind the unit.
 
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Old 03-15-05, 11:35 AM
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Racraft,

Just out of curiosity, I am wondering about the history of the rule against plugging dishwashers in under the sink base. In a former life I was a maintenance supervisor at a 250 unit apartment complex which was built in the early 70s. Every unit had a receptacle under the sink base that was shared between the disposer and the diswasher. When did this cease to be permitted? (Also, by todays standards I understand that any cord-and-plug connected equipment that is fastened in place cannot occupy (draw) more than 1/2 of the circuit's capacity, so it is unlikely for that reason alone that these appliances could share a duplex receptacle anymore.

Juice
 
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Old 03-15-05, 11:50 AM
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Actually, I mentioned that rule to Bob the other day, and he asked me for the same history. I didn't know. I do know that the rule was clarified in the 2002.

Whether or not a dishwasher and disposal on the same circuit is a good idea depends on the circuit, the dishwasher, and the disposal. A 20-amp circuit can support a dishwasher without a water heater plus a 1/2 HP disposal, but a 15-amp circuit cannot support a dishwasher with all the fancy features plus a 1 HP disposal. One of the reasons you probably want them on separate circuits is so as not to constrain your future choices of dishwashers and disposals.
 
  #5  
Old 03-15-05, 11:57 AM
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I do not know when it became a requirement for that the dishwasher (if plugged in) must be plugged in directly behind it, not off to either side. My own kitchen has the dishwasher plugged in under the sink, sharing the receptacle with the disposal.

I asked John Nelson this same question *when did it become code). He didn't answer that part of my question.

"Also, by todays standards I understand that any cord-and-plug connected equipment that is fastened in place cannot occupy (draw) more than 1/2 of the circuit's capacity, so it is unlikely for that reason alone that these appliances could share a duplex receptacle anymore."

I am not aware of this requirement.
 
  #6  
Old 03-15-05, 12:38 PM
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NEC - 210.23(A)(2) says "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 equipment not fastened in place, or both, are also supplied." So I guess if this receptacle is dedicated to the disposal or dishwasher, you can exceed 50% for the fastened in place equipment. (?)

Juice
 
  #7  
Old 03-15-05, 12:45 PM
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Both the dishwasher and the disposal are "fastened in place." Both are also cord and plug connected. Since nothing else is on this circuit, this rule does not apply.

At least that's how I read it.
 
  #8  
Old 03-15-05, 12:48 PM
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That is also how I always read it, too. But reading, just today, that you can't plug a dishwasher in under the sink base is new to me. I'm just curious when this changed, and how come?

Juice
 
  #9  
Old 03-15-05, 06:12 PM
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Well, since this keeps coming up, I suppose it's time to be more precise.

422.16(B)(2) Buil-in Dishwashers and Trash Compactors ... shall be permitted to be cord-and-plug conected ... where all of the following conditions are met ... the length of the cord shall be 3 feet to 4 feet, measured from the face of the attachment plug to the rear of the appliance ... and receptacles shall be located to avoid physical damage to the flexible cord ... and the receptacle shall be located in the space occupied by the appliance or adjacent thereto." The phrase "adjacent thereto" gives you a little wiggle room, but the four-foot maximum cord length doesn't offer much.

The 1999 code had the same rules (in 422-8).
 
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