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I need to provide power to a instant hot water dispenser that I recently installed myself in our circa 1950 home. I'm about to have my dishwasher replaced and am wondering what the typical electrical connection is provided behind dishwashers so I can be prepared with the right parts when the dishwasher installers arrive.

I attempted sliding the dishwasher out myself to check, but it seems that I probably need to at minimum remove the copper hot water pipe, which is more of a project than I'd like. Is there typically a standard dual outlet behind the dishwasher?

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3 Answers 3

up vote 5 down vote accepted

Dishwashers can be either hardwired, or cord-and-plug connected. Check the owners manual of the unit you have, but in most cases the decision is left to the installer.

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From a random Maytag Dishwasher Installation Guide (PDF)

In newer homes you'll commonly find a 125V NEMA 5-15R receptacle supplied by a 20 ampere circuit, used to supply a dishwasher and disposer. In this case, the receptacle is typically installed in the cabinet under the sink. If you don't have a receptacle under the sink, it's not likely that the dishwasher is cord-and-plug attached.

The National Electrical Code, specifies that all outlets must be accessible. Because of this, a receptacle installed in a location that requires the removal of the dishwasher is not code compliant. i.e. If you can't find where the dishwasher is plugged in, it's likely hardwired.

Checking the wiring for the disposal, might give you some clues as to how things are wired.

You might also find This answer useful, when trying to figure out what you can connect to the circuit.


Code that allows Garburators and dishwashers to be cord-and-plug-connected

National Electrical Code 2014

Article 422 Appliances

II. Installation

422.16 Flexible Cords.

(B) Specific Appliances.

(1) Electrically Operated Kitchen Waste Disposers. Electrically operated kitchen waste disposers shall be permitted to be cord-and-plug-connected with a flexible cord identified as suitable for the purpose in the installation instructions of the appliance manufacturer, where all of the following conditions are met:

(1) The flexible cord shall be terminated with a groundingtype attachment plug.

(2) The length of the cord shall not be less than 450 mm (18 in.) and not over 900 mm (36 in.).

(3) Receptacles shall be located to avoid physical damage to the flexible cord.

(4) The receptacle shall be accessible.

(2) Built-in Dishwashers and Trash Compactors. Built-in dishwashers and trash compactors shall be permitted to be cord-and-plug-connected with a flexible cord identified as suitable for the purpose in the installation instructions of the appliance manufacturer where all of the following conditions are met:

(1) The flexible cord shall be terminated with a grounding type attachment plug.

(2) The length of the cord shall be 0.9 m to 1.2 m (3 ft to 4 ft) measured from the face of the attachment plug to the plane of the rear of the appliance.

(3) Receptacles shall be located to avoid physical damage to the flexible cord.

(4) The receptacle shall be located in the space occupied by the appliance or adjacent thereto.

(5) The receptacle shall be accessible.

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As to the outlet, it depends on the house. Some will have a regular outlet, while others may have just an electric box for hardwiring the dishwasher. What I would be worried about is overloading of the electric circuit. Dishwasher, disposer and a water heater all draw quite a bit of current, so you may have to run an additional circuit from your panel. What you may want to do is check to see if both the disposer and the dishwasher are on the same breaker. If so, is the breaker at least 20A (it says on the breaker)?

If you have any room in your budget I would also replace the copper water line with a braided dishwasher hose. Copper lines tend to kink when you move the dishwasher in and out restricting the water flow. Builders tend to use them because they are cheaper but you can get a braided dishwasher hose for under $25.

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The answer depends on your location.

In the UK, dishwashers are often connected to a normal 13 A, 240 V wall outlet on the kitchen ring (probably a 32A ring circuit separate from electric oven circuit etc).

I'm not really familiar with the US but I expect it involves a baffling array of single and split-phase options with numerous possible combinations of connector depending on the current and voltage required by a specific appliance. See What types of electrical outlets are found in a typical home in the USA? - From what I've read it usually involves a dedicated 20A circuit hardwired in a junction box using wiring nuts - so I guess there may not be a 5-15 outlet nor even a 5-20 or L5-20.

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120V power in the USA doesn't use a baffling array of receptacles - the most common receptacles by far are the 15A and 20A receptacles pictured in the answer you linked to. A 15A plug will fit into either outlet, a 20A plug (which is rare) only fits in a 20A outlet. Occasionally you might see a 30A 120V outlet (usually for something like an air conditioner), but those are rare. Since 15A outlets have been the standard for so long, almost all small home appliances are designed to work with a 15A outlet. Some high-end dishwashers do require a 20A circuit, but most mainstream units are still 15A. –  Johnny Dec 11 '13 at 16:35
    
@Johnny: Yes sorry, I must stop teasing leftpondia about stuff. –  RedGrittyBrick Dec 11 '13 at 16:43
    
You can tease all you want - there are a bewildering array of possible outlet styles especially in industrial settings, but I didn't want the asker to think that he was going to have to get out a big chart of possible outlet styles when a home dishwasher outlet is almost certainly a common 15A or 20A grounded outlet. –  Johnny Dec 11 '13 at 16:55
    
To be fair, 220/240 in the US can be a mismash but dishwashers fall in the 'standard appliance' category. –  Aaron Dec 11 '13 at 17:38
    
In our house there are only 3 outlets that aren't 5-15. One for the stove, one for the clothes dryer (unused) and one for a travel trailer. About the only time you use an outlet that isn't a 5-15 or 5-20 is when you are using more than 20 Amps or need 220/240 volts. The main reason is that our cords don't have a fuse in them, to prevent people from plugging in a cord that would melt before the breaker trips. Or to prevent people from plugging in something that only uses 120V into a 240V outlet. –  Brad Gilbert Dec 12 '13 at 1:28

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