Dishwasher electrical connection

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  #1  
Old 02-04-02, 02:37 PM
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Dishwasher electrical connection

I am planning on remodeling my kitchen, which will include installing a dishwasher. Is it acceptable to install a normal electrical outlet, then just plug in the dishwasher? Or must the dishwasher be hard-wired? Does it need its own circuit? Thanks.

Jon
 
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  #2  
Old 02-04-02, 02:47 PM
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The dishwasher should be on a dedicated circuit and on whether you are allowed to plug it in or hardwire it will depend on the manufacturers recommendations, some major appliances must be hardwired according to their UL listing others have the ability to be plug and play. You should refer to your owners manual on the recommended hookup, wire and breaker size for the unit you have purchased.
 
  #3  
Old 02-04-02, 03:55 PM
Wgoodrich
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If you are installing a built in under the cabinet dishwasher most often they have a junction box designed to accept the power cable using a romex connector. Do not install a receptacle flush in the wall behind the dishwasher, it would not be considered as accessible. If you want to install a receptacle then install a rubber cord to the dishwasher install the receptacle under the kitchen sink so that receptacle is accessible. Then be sure that the cord does not have to be more than 4' in length. Dishwashers have a maximum cord length of 4'. 422.16.B.2

Hope this helps

Wg
 
  #4  
Old 02-06-02, 07:29 AM
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Thanks, guys.
Follow-up question: I have not purchased the dishwasher yet; what percentage require hard-wiring as opposed to plug-in? Is one preferable over the other?

I'm leaning toward just installing an outlet under the sink. Because I now use a 'portable' dishwasher - and just plug it into an existing outlet - I'm not sure I understand why a dedicated outlet is required/preferred. Why not just extend wiring from the outlet I currently use and add a new under-the-counter receptacle?

Thanks for all the help.

Jon
 
  #5  
Old 02-06-02, 09:33 AM
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the type of dishwasher and type of connection are a matter of personal choice. I don't think one is superior to the other there are advantages to both methods. I personally like it when I can disconnect at the appliance and not have to run up and down to panels to service a unit.

The reason for a dedicated circuit is normally the amount of amps one of these units draw, if it was connected to another device you might end up with a lot of nusence tripping. This can be interpeted a few ways according to the NEC but without going into to much detail I think you'll find using a dedicated circuit is more effieccent in the long run.
 
  #6  
Old 02-09-02, 09:12 AM
Wgoodrich
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210.23.A.2 limits any fastened in place appliance to be limited in amps not to exceed 50% of the branch circuit supplying its power. If you install an undercounter dishwasher it would be considered as fastened in place therefor on a 20 amp branch circuit you must not exceed 50% being 10 amps rating of that dishwasher. A dishwasher will pull more than 10 amps.

If the dishwasher is a portable dishwasher this rule would not apply to the 50% of a branch circuit limitation because it is portable and does not have a specific location assigned to it, but like Gard said you will most likely have problems with the breaker tripping if any other loads like a toaster etc. is likely to overload that circuit with the dishwasher running.

Hope this helps

Wg
 
  #7  
Old 02-09-02, 09:19 AM
hotarc
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Wg, does that mean that a 20 amp circuit is not sufficient for a permanent dishwasher since they will pull in excess of 10 amps? I have seen tons of dishwashers connected to 20A circuits. Should a dishwasher be on a 25 or 30 amp circuit instead?
 
  #8  
Old 02-09-02, 03:31 PM
Wgoodrich
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hotarc, I was answering his question as he asked it. I guess I may have created an misconception to what I was saying if out of context with his question.

210.23.A says that any utilization equipment [fastened in place type] connected to a branch circuit with lights or cord and plug equipment also on that circuit. This circuit is a shared branch circuit both utilization equipment and general use receptacles on the same circuit. You don't know what else will be plugged into those convenience outlets so the limit of the utilization [fastened in place] equipment is limited not to exceed 50% of that multiuse branch circuit. This rule is limited to 15 or 20 amp rated branch circuits with both receptacles or lights on the same circuit as the fastened in place equipment. This would mean that if receptacles are on the same branch circuit as a fastened in place piece of equipment then that fastened in place piece of equipment can not be rated in amps more than 50% of the ampacity of that branch circuit. 15 amp branch circuit would allow a fastened in place piece of equipment to be placed on that circuit with an amp rating of no more than 7.5 amps, if lighting or rececpatcles are also on that circuit. A 20 amp branch circuit discribed in the above sentence would be allowed up to 10 amps rating of that one piece of utilization equipment.

210.23.A.1 allows a single dedicated branch circuit to be loaded up to 80% of that branch circuits ampacity rating. This would mean that you could install a 15 amp rated circuit and serve one piece of equipment with nothing else on that circuit rated in amps up to a maximum amp rating of 12 amps on that 15 amp branch circuit that is dedicated only to that one piece of utilization equipment. A 20 amp rated branch circuit that is dedicated to only one piece of utilization equipment may be loaded up to 16 amps rating of that one dedicated piece of utilization equipment.

Sorry for not being clear on what I was saying

Wg
 
  #9  
Old 02-09-02, 05:48 PM
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Wg has stated that you should not put a receptacle on the wall behind the dishwasher, due to the fact that the receptacle would not be "accessible".

I believe this analysis to be incorrect. I will refer you to the same section of code that Wg mentioned: 422-16(b)(2). Note that it says that the length of the cord shall be between 3 and 4 feet, measured from the face of the attachment plug to the plane of the rear of the appliance. I have been reading "Interpreting the National Electrical Code" by Truman Surbrook and Jonathon Althouse. This book is based on the 1999 NEC, although there are no differences between the 1999 and 2002 code in this article. They mention that the cord itself may really be slightly longer than 4 feet, because the measurement is not taken along the cord itself. This is a difference between the 1996 and the 1999 NEC. Surbrook and Althouse give a diagram to explain this rule, and the diagram clearly shows the receptacle on the wall behind the dishwasher. The receptacle is only accessible if you pull the dishwasher out. Note that the code-mandated cord length will only allow the dishwasher to be pulled out 4 feet before you'd be forced to unplug it.
 
  #10  
Old 02-10-02, 04:43 PM
Wgoodrich
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I not only have read a comment to a receptacle installed behind a dishwasher that is screwed into place as a finished product and plumbed into place can be considered as accessible. I read this comment in the interpretations and Code changes in the 2002 NEC / IAEI code change book and slide program. I also heard at the convention the same commentary by the expert Code panel presenting the 2002. Both support what John said in his previous reply. However in reading the wording of the NEC I am hard pressed seeing where they are coming up with this interpretation. While I personally have heard strong support in what John claims from some high up there Code experts and in the print of the Code Change book of 2002 NEC I just don't see it in print in the NEC. Read the following and tell me where they are getting that interpretation;

2002 NEC

422.16.B.2.5

(5) The receptacle shall be accessible.

Article 100

Accessible (as applied to wiring methods). Capable of being removed or exposed without damaging the building structure or finish or not permanently closed in by the structure or finish of the building.


I guess maybe they are considering that built in dishwasher not being a finished surface but a readily removable panel that just happens to be plumbed in place. Don't make sense in that interpretation. Would like enlightened where the got that in mind when they wrote the Code changes.

422.16.B.3 states that you may plug connect but does not require the accessible rule as in dishwashers.

John reread the part in the Code changes and see if it names ovens, counter mounted cooking units, and dishwashers. Let me know if they specifically mention dishwashers in that exemptions.

Not saying that you are wrong, just don't get where the have the support of that exemption stance of dishwashers.

Curious and flustered

Wg
 
  #11  
Old 02-10-02, 05:21 PM
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Pulling a dishwasher out is certainly a lot easier than removing a range or oven. The two screws that attach the dishwasher to the counter are pretty wimpy, and are there just to keep the dishwasher from rocking. Plumbing is easy to remove with a simple wrench, so that only takes a few seconds too. Some dishwashers with sufficient slack in the copper tubing and plastic drain line may be pulled out without disconnecting the plumbing.

It's almost as hard to pull out an ice-making refrigerator full of food as it is to pull out the dishwasher (well, that may be an exageration).

I have to admit that I'm Monday-morning quarterbacking this one.
 
  #12  
Old 02-11-02, 11:39 AM
Wgoodrich
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(5) The receptacle shall be accessible

The part referring to couter cook tops and ovens say nothing about the j-box or receptacle required to be accessible. They also don't have the length limitation of hte cord. Yet the dishwasher states both limitations.

The book you referred to if I understand the book you are quoting from I read and know it said what you quoted. If I am right about the Code change book you referred to this is the first time that IAEI and NEC worked in cooperation with each other in writing that code change book. In my mind it is a good book with strong knowledge behind it.

I just don't see a change in wording between Code versions that reversed the accessibility ruling of that receptacle. i am not saying that it is illogical. I just can't see any wording changed that would reverse the accessible ruling on a receptacle mounted behind that dishwasher. John do you see any word changing between the 99 and hte 02 NEC that would have triggered the statement saying that a receptacle behind the dishwasher is now ok. Why the logic in the cord limitation limited to dishwashers also.

Not saying they are wrong just somewhat lost as to what triggered this interpretation.

While your looking between the 99 and hte 02 see if you see a change in the definition of "accessible" in article 100. This may be where they are coming from.

Curious

Wg
 
  #13  
Old 03-24-13, 07:43 PM
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Lightbulb The NEC is really more relaxed when it comes to ampacity!

There was a wrong interpretation of 210.23.A.1 posted, saying that it requires max 80% rated ampacity load on individual branch circuits, or even 50%, etc. That's not the case if you have individual branch circuits. The 210.23 subparts (A, etc) only apply on NON-individual circuits! If you have an individual branch circuit, then it can supply full rated load:

210.23 In no case shall the load exceed the branch-circuit ampere rating. An individual branch circuit shall be permitted to supply any load for which it is rated. <--- individual | non-individual ---> A branch circuit supplying two or more outlets or receptacles shall supply only the loads specified according to its size as specified in 210.23(A) through (D) and as summarized in 210.24 and Table 210.24.

Really when you have an individual branch circuit, things are very simple. For example, 210.21(B)2 and 3 don't apply. The 210.21(1) states:

(1) Single Receptacle on an Individual Branch Circuit.
A single receptacle installed on an individual branch circuit shall have an ampere rating not less than that of the branch circuit.

That means that if you have a 20A individual branch circuit, the only limitation is that you must use a 20A-rated receptacle, that's all. It's probably wise to provide such circuits for both microwave and the dishwasher, to allow future upgradability. It's also wise to provide a 60A circuit for the range/oven combo, to allow for future upgrades to induction cooking etc. -- obviously where there's panel capacity to do so. You can always oversize the cable and put a smaller breaker and matching receptacle on it.

Personally I find the receptacle-behind-dishwasher concept to be ridiculous. Most dishwashers can't really be moved even if you unbolt them from under the countertop. You really don't want to flex the copper water supply tube, you must disconnect it first and doing that with energized dishwasher is beyond stupid. Don't forget that the 4 feet max dishwasher cord length requirement counts from the rear plane of the dishwasher to the face plane of the plug! You may have a shorter requirement given by the dishwasher manufactuer. For example my Whirlpool has the junction box in the front, and specifies 6 feet max cord length. This leaves one with less than 4 feet from the rear plane, but long enough to route around and into the undersink cabinet for accessibility. The manufactuer's requirement overrides the NEC minimum of 3 feet from the rear plane of the dishwasher as well, and that's OK since that requirement is needed to maintain the listing of the dishwasher!
 
  #14  
Old 03-24-13, 08:05 PM
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Welcome to the DIY forum, KubaRebo! It is good to get a code expert on board. Understand that this is an old thread but your expertise is welcomed.
 
  #15  
Old 03-24-13, 09:04 PM
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Yes, welcome to the forums. Code expertise is always welcomed but would you mind pitching in on the active threads wherever you think you can help. Thanks

This thread has run its course so I'm closing it.
 
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