Wiring a dishwasher

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  #1  
Old 11-11-14, 11:26 PM
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Wiring a dishwasher

Now I know this isnt supposed to be done, but I tried to use romex to make a temporary power cord tonight to use our dishwasher in the house we just moved into. I know the receptacle on the wall works fine because Ive had a few different things plugged into it. I connected white-silver Black-gold ground-green on the 3 prong plug. and white-white black-black and ground-green on the dishwasher. Its only a 3 or 4ft run of brand new 14-2. When I tried to plug it in, the lights dimmed and I immediately smelled something burning. I just touched it to the recep and pulled it out right away, didnt even get it plugged in all the way. Noticed the ground prong has a burn on the tip. Why would this happen?
 
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  #2  
Old 11-12-14, 12:04 AM
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The method isn't correct but the connections appear to be correct.

That leaves you with an improperly wired receptacle or a short in the dishwasher.
You'd need a meter to check for shorts in the dishwasher.
 
  #3  
Old 11-12-14, 11:22 AM
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How would I go about checking it for shorts?
 
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Old 11-12-14, 12:17 PM
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Replacement plugs aren't designed for solid wire.
Not to say that's your problem, But before checking for shorts, replace cord.
Buy a replacement cord with molded plug, such as 6' disposal cord.
Connect cord ground to DW ground, either EG screw at box or green wire.
Connect cord hot (smooth on insulation) to black.
Connect cord neutral (ribbed insulation) to white.

Once cord is properly connected, including proper strain relief, and before plugging in unit:

Check continuity between hot and ground prongs of plug, there should be none.
 
  #5  
Old 11-12-14, 01:33 PM
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Thanks. Ill stop at menards today and buy a cord for the dishwasher and disposal. Weird thing is, I took The recep out to check wiring. Its old 2 wire MC, no ground. Everything looked ok. I took the plug off of the romex and attached the romex to the recep, flipped the breaker on, and the dishwasher powered up as it should. I took the romex off the recep, re-wired the plug in the same way and plugged it in and it works fine now. Makes no sense to me..

One issue I do see with this old wiring in the house is it looks like its just 2 hot wires, both wires are black.
 
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Old 11-12-14, 02:34 PM
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Two blacks would give you 240 volts. Are you looking at cloth covered wires. Sometimes with age the white looks the same color as the black. To determine which is neutral measure from a known good ground to each wire. The white will be ~0 volts and the black ~120v.
 
  #7  
Old 11-12-14, 10:40 PM
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that could very well be it all the wiring and everything else in the walls is just filthy old dusty and covered in spider webs. I just didnt know if there was a time where they used the same color wire with some sort of other markings to determine which was which.

Anyway I just picked up a cord from menards for $5 and wired it up tonight. Dishwasher works good. Thanks
 
  #8  
Old 11-13-14, 09:38 AM
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I would bet that the manufacturer on the dishwasher does not allow operation on an ungrounded circuit as the dishwasher probably has exposed metal parts (like the toe kick). You should verify this with the installation manual before proceeding. At the very least, I would add GFCI protection to this circuit. The better option would be to install a new grounded circuit.
 
  #9  
Old 11-13-14, 09:47 AM
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I would second that. Check the outlet for ground. Test hot to box and hot to cable sheath, should read same as hot to neutral. ~120 volts.
You also need to be careful working under the dishwasher, some components are intentionally left ungrounded. Always turn off power to circuit before working on unit.
 
  #10  
Old 11-13-14, 08:48 PM
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Well nevermind my last post. I had the outlet just hanging out of the wall when I tested it to make sure it was working. I put the outlet back in the box and when I plugged the dishwasher in, the lights flickered again and I got a poof of smoke under the dishwasher where the steel braided supply line was touching the frame. I tested the hot wire with one lead on the box and it reads 120v so the box is grounded.

Is the outlet grounded to the box by the screws holding the recep to the box? or does it need to be grounded using wire to the box?

Sorry im pretty new to the AC electrical systems, I have just about all the tools i would need but 90% of my electrical knowledge is in DC in automotive applications

AC makes me nervous for obvious reasons, I always shut the circuit off before touching anything.
 
  #11  
Old 11-13-14, 09:00 PM
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Unplug dishwasher and turn off breaker to receptacle. Please wait for a professional electrician to get back to you.
While waiting, just a few questions:
1) Did breaker trip?
2) Did you check continuity at dishwasher plug? Hot to ground, no continuity?

Also check wires at wall box. Inspect for any cuts or nicks in wires. Inspect receptacle terminals and make sure wires are not stripped too long (allowing them to touch metal box).
Some metal boxes are smaller than others, when installing receptacle back into box, ensure no parts of receptacle are touching box.
 
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Old 11-13-14, 09:03 PM
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At this point in time..... you have a short between the hot wire and ground or in this case.... the frame of the dishwasher. It would appear that you didn't have the dishwasher grounded thru the power cord so the water line was the ground source.

STOP powering up the dishwasher. You need to use an ohmmeter set to ohms. You need to connect to the frame of the dishwasher and the black wire in the junction box. You should not see continuity.

You will most likely need to follow just the black hot wire from the junction box to where it goes into the machine. If it's visibly ok then your next step will probably be opening the door to access the wiring to the controls.

There should be a wiring diagram attached to your dishwasher. Look around and see if you can find it. Sometimes it's in a plastic bag and taped to the frame.
 
  #13  
Old 11-13-14, 09:12 PM
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Breaker hasnt tripped yet. I checked continuity on the dishwasher plug and I dont have anything between any combination of hot, neutral or ground. I do however have 120v between neutral on the recep and the box. and nothing between hot and the box
 
  #14  
Old 11-13-14, 09:23 PM
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You need to pull the receptacle out of the box. Check from white wire to cold water pipe or kitchen faucet or even the frame of the dishwasher if the flex water line isn't completely melted.

Now do the same for the black wire.
Now check from the box to ground.
 
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Old 11-13-14, 09:25 PM
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I do however have 120v between neutral on the recep and the box.
It should be ~0 volts. Hot should be ~120 volts to ground.
 
  #16  
Old 11-13-14, 09:26 PM
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The breaker is out of the box and was when I did that last test. Ill go check with it against the dishwasher frame now
 
  #17  
Old 11-13-14, 09:31 PM
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Thats what I thought, Not sure why this would be tho? and the dishwasher is the only thing that has this issue.. I just used the outlet this way today to plug a light into, and cooked a pizza with a pizza cooker plugged into it. Must be because its grounding thru the plumbing I guess and the other appliances arent?
 
  #18  
Old 11-13-14, 09:50 PM
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Electrical appliances usually come wired with a polarized two prong plug (one prong wider and one narrower). However, the appliance has no idea if the polarity on that receptacle is correct. That means the pizza oven doesn't care if the hot and neutral are reversed.... it will still heat up.
 
  #19  
Old 11-13-14, 10:06 PM
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Makes sense. Well I have 120v between the kitchen sink (stainless) and the recep box in the wall.
 
  #20  
Old 11-13-14, 10:08 PM
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While waiting for further help, I would completely remove dishwasher. Undo all electrical and plumbing connections and remove from opening.
Lay dishwasher on it's back and inspect underside wiring harness for any nicks or slices in wires.

If you had a hard time getting unit into opening, which is common, you may have damaged some wires under unit.
 
  #21  
Old 11-13-14, 10:16 PM
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Ill pull it out and check since It did smoke the last time I plugged it in. But do you still think it has anything to do with the dishwasher? Now that I see I have 120v between the sink and the outlet box (with the outlet not mounted in it) I am assuming I have an issue with a neutral wire touching plumbing somewhere?

Dishwasher slides under the cabinet easily, and I can see the wiring for the most part from under it by removing the kick plate. None is on the ground or anywhere that it could be damaged while moving the machine in and out
 
  #22  
Old 11-13-14, 10:56 PM
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Shut off breaker. I want to help but this is beyond my troubleshooting ability. Wait for a good answer from an electrician.
If you have 120V from sink to box, this means box is energized. Not good.
I am cautious, and I would even suggest shutting off all power until this is resolved.
 
  #23  
Old 11-13-14, 11:53 PM
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Well I do appreciate your input at this point I'm new enough to where any advice is useful to me. One thing that may be worth mentioning is I did see one bare copper wire on the neutral bar in the panel.

Just to clarify before I goto bed: Between the sink and Hot I get 120v. Between the Sink and Neutral i get 0v. And between the sink and recep box I get 120v. So the sink/plumbing is hot. Also using a circuit tester just says reverse polarity on the outlet in question but I am sure the outlet itself is wired right color-wise at least. And the original issue doesnt occur unless the outlet is grounded to the box (screwed into it.) I had the dishwasher running and tested out the disposal Via the same outlet last night while the outlet was hanging out of the box with no issue
 
  #24  
Old 11-14-14, 07:25 AM
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I think it is time for someone on site to help sort this out, especially if the plumbing may be energized.
 
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Old 11-14-14, 07:33 AM
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Yes, you need an electrician to sort out this mess. Be sure it is a licensed electrician not just a handy man.
 
  #26  
Old 11-14-14, 07:48 AM
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I would second calling an electrician. We could probably sort this out using people here,
But this sounds like just too much of an immediate safety concern.
Please get this fixed ASAP, and stay away from any plumbing fixtures.
 
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Old 11-14-14, 08:23 AM
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Between the sink and Hot I get 120v. Between the Sink and Neutral i get 0v. And between the sink and recep box I get 120v. So the sink/plumbing is hot.
It sounds more to me like the box is energized rather than the plumbing. This does need to be sorted out soon for safety. I agree that a good electrician should called.
 
  #28  
Old 11-14-14, 10:14 AM
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I believe I have the skill set to figure this out.. id like to learn more about AC systems so I can be comfortable working with them. Its obviously something that needs to be resolved I know. I just installed the sink, installed a clothes washer in the basement, have touched plumbing tons of times in the basement this past week. If I cant figure this out today I will call someone but I like to give it a shot at least. Im going to go up in the attic and take a look at the wiring and see if I can find anything. This outlet doesnt feed any other outlets. So if I disconnect it from a junction box upstairs and no longer have this issue than I know its something after that junction box.

Unless there's a whole other dimension to this issue that im not aware of?
 
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Old 11-14-14, 10:26 AM
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OK,
Let's forget about the dishwasher then and assume for now that's not the problem.

It's much easier if this receptacle box only has a black and a white, which sounds like the case.

Test all aspects of receptacle and box. Report back.
Hot to neutral - 120V
Hot to box - 120V
Neutral to box - 0V
Neutral has continuity to box
Hot does not have continuity to box

Sink does not have continuity to hot.
 
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Old 11-14-14, 10:48 AM
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If you turn off the breakers one at a time is there one that makes the voltage on the sink to ground go away?
 
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Old 11-14-14, 10:53 AM
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Hot to Neutral is 120v
Hot to box is about 0v
Neutral to box is 120v
Neutral doesnt have continuity to box
Hot does have continuity to box

Sink has very weak continuity to hot

Sounds like the hot and neutral are switched somewhere?
 
  #32  
Old 11-14-14, 10:57 AM
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If i turn the kitchen breaker off the sink-box no longer have power
 
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Old 11-14-14, 10:59 AM
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Are both the wires black??
It sounds like you do not know which wire is hot and which wire is neutral.
Identify the wires and mark them.
Hot will read 120V to box
Neutral will read 0V to box

I'm sorry, this is going to be a slow process.
 
  #34  
Old 11-14-14, 11:04 AM
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No, ones white and ones black. White wire to box shows 120v black wire to box shows 0v
 
  #35  
Old 11-14-14, 11:18 AM
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Somewhere a connection is wrong if the white is hot.
 
  #36  
Old 11-14-14, 11:18 AM
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Check voltage from box to cold water pipe under sink, not the sink itself.
Report back. Use a wire extension on probe if needed.
 
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Old 11-14-14, 11:37 AM
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I'm confused earlier you wrote:
One issue I do see with this old wiring in the house is it looks like its just 2 hot wires, both wires are black.
Now you write:
No, ones white and ones black.
Is this just a short cable tied into the older wiring. If so you need to look at the box where it is connected.
 
  #38  
Old 11-14-14, 11:56 AM
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I have 120v between the sink/box, pipes/box and dishwasher frame/box since the dishwasher is still hooked up to water line but power is disconnected.

The wires are just old and dirty it was hard to tell at first that they were different colors. But one has white on it for sure. This is old cloth covered wires in that MC armor throughout most of the house. Some romex here and there. Ill go check the box that this outlet runs to up in the attic
 
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Old 11-14-14, 12:00 PM
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I strongly recommend you get an electrician out. I know you want to learn about AC, as we all do, but there are easier and safer ways to start.
 
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Old 11-14-14, 01:32 PM
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I agree with Brian. We can only answer the questions you ask and use the information you give. We can't answer the questions you don't know enough to know you should ask ask or use the information you don't know enough to know you should give us.
 
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