Need help grounding dishwasher.

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Old 01-04-16, 04:03 PM
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Need help grounding dishwasher.

Hey guys, replacing an old dishwasher.

New dishwasher has a cord with a plug.
Old dishwasher was hard wired.

So I cut the plug off the new dishwasher and I am going to hardwire it however it is an older house and just has a black and white wire coming through flex conduit in a hole in the wall. There is no ground wire or any box to ground to.

What should I connect the green ground wire from the dishwasher to?
 
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Old 01-04-16, 04:12 PM
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So I cut the plug off the new dishwasher
You should not have done that. Obviously the manufacture intended for it to be plugged in. You will probably need to buy a replacement cord with plug cap or at least a new plug for the end of the cord unless the manufacturer provided instructions for hard wiring. That would involve removing the cord from the DW's junction box and replacing it with a cable. You can't just connect the house cable to a cut off cord.
it is an older house and just has a black and white wire coming through flex conduit in a hole in the wall.
Unless that is the newer type of metallic cable with a bonding strip you need to replace it with 12-2 or 14-2 NM-b with ground. You need to install a box and receptacle for the cord from your dishwasher. If it is the newer style cable you need to install a metal box. The cable sheath will serve as ground.
 
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Old 01-04-16, 04:23 PM
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So you are saying that I need to run an entire new line from the circuit breaker panel all the way to the dishwasher? And then install an outlet box behind the dishwasher?
 
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Old 01-04-16, 04:46 PM
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So you are saying that I need to run an entire new line from the circuit breaker panel all the way to the dishwasher? And then install an outlet box behind the dishwasher?
Basically yes if the existing metallic cable is old style Bx and therefor has no bonding strip. You could also run just a ground wire but it is usually just as easy to run new cable since under NEC before 2014 the ground must go back to the panel. If you are under 2014 NEC you can run a ground off the closest grounded circuit.

I suspect the existing circuit is not a dedicated circuit. If it isn't a dedicated circuit it is grandfathered but best practice would be to run a new circuit because the DW should be on a dedicated circuit.
 
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Old 01-04-16, 05:26 PM
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There is a GFI nearby the cabinets. Would it be possible for me to run a separate ground wire to the GFI outlet or box and then use the existing black/white 2 wire coming out of the wall?
 
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Old 01-04-16, 05:27 PM
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The receptacle should not be behind the DW. It can be in the sink cabinet. It would also need gfi protection under the 2014 code.
 
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Old 01-04-16, 06:09 PM
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Or can I tap into the GFI up above the counters and run wires down to make another GFI under the sink?
 
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Old 01-04-16, 06:12 PM
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There is a GFI nearby the cabinets. Would it be possible for me to run a separate ground wire to the GFI outlet or box and then use the existing black/white 2 wire coming out of the wall
Yes if the GFCI has a true ground. How long is the MC? Can you get the MC in to a cabinet next to the DW? If that was under the GFCI receptacle that would make running the ground easy.
Or can I tap into the GFI up above the counters and run wires down to make another GFI under the sink?
No, a DW can not be on the counter top receptacle circuits.
 
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Old 01-04-16, 06:21 PM
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What is an MC? Sorry I'm quite new to electrical.

How do I tell if that GFCI has a true ground?
 
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Old 01-04-16, 06:24 PM
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MC is metallic cable such as what you have coming out of the wall. If the cable coming into the GFCI receptacle has a bare ground wire then you have a ground.
 
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Old 01-04-16, 06:34 PM
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Got it. I will have to check for ground wire on the GFCI tomorrow when I'm back at the property.

So if the GFCI does have a bare ground, I can just use the white and black coming out of the MC and then run a third wire up the to all to the GFCI for a ground and I'm done?

Thanks for the help,
David
 
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Old 01-04-16, 07:16 PM
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Yes, but the receptacle can't be behind the dishwasher. That would make it to difficult to reset if the GFCI trips, and they do sometimes. Code says easily accessible. That is why PCBoss said it needs to be in a cabinet next to the dishwasher not behind it.
 
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Old 01-04-16, 08:08 PM
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Can you post a picture of the cable?
 
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Old 01-04-16, 08:27 PM
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Well I am not installing a new receptacle.

If I understand what your saying I can just tap into the existing gfci up above the counter for a ground only and then use the existing wires coming out of the wall for power.

And sorry, it's red and white coming from the wall. Not black and white. But in assuming red would be hot and white is neutral?

Or can I just use the red and white and turn those into a GFCI receptacle? But I would still need a ground correct? Or would that metal conduit it's already in automatically ground it? and then I just ground my green wire to the box?

Here is a photo of wires from the wall, and then I have a green wire coming from the dishwasher as well as my + and -.
[ATTACH=CONFIG]61082[/ATTACH]
 
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Old 01-04-16, 08:54 PM
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I am not ignoring anyone's advice, I'm just confused on the proper way to do this.

Your saying that I should run an entirely new line from the panel and install a GFCI in the sink cabinet correct?

Or run a new line and just hard wire it, but either way you recommend running the new line. Which I'm fine with I just want to know what the best way to do this is.

Sorry, I thought you were saying I could just tap into the GFCI above the counters for a ground only and then still use the red/white.
 
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Old 01-04-16, 08:59 PM
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The red wire indicates you have Greenfield (flexible metallic conduit) not metallic cable. That is coming from a box some where. Best guess is a switch on the counter back splash. You need to find that box. If you are near Chicago then you may have metal conduit. If so that will solve the grounding problem.

Apologies for not picking up on the flex conduit you mentioned in the first post.
 
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Old 01-04-16, 09:02 PM
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There is no switch in the kitchen controlling power to those wires. There is a breaker marked dishwasher on the panel though.

I am about 45 min outside Chicago.

Still unclear on how to go about this.

I will cut into the drywall tomorrow and see if I can trace where that flexible conduit is coming from.

My guess is they have it tapped into the GFCI above the counter already.
 
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Old 01-04-16, 10:18 PM
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Before cutting the wall open the GFCI receptacle and look for a red wire.

Some explanations:
Hard wired dishwashers are often wired to a switch to meet the code requirement for a disconnect within sight of the dishwasher. A plug counts as a disconnect so plugs are used so no switch needed.

Metal conduit is required for wiring in Chicago. When wiring with conduit a red wire is often a wire controlled by a switch.

When non flexible metal conduit such as EMT is used it serves as ground. Flexible conduit can not serve as a ground unless it has a bonding strip. Old greenfield didn't.
 
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Old 01-04-16, 11:45 PM
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If that is Greenfield you should be able to pull a ground into the conduit.
 
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Old 01-06-16, 08:13 AM
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UPDATE:

I opened the outlet box today, and found that the red and white wire running to the dishwasher are connected and spliced up into the switch on the wall.

However - I am fairly certain the dishwasher still works even if that switch is OFF so I do not think the switch directly controls the dishwasher, maybe they just tapped into it for power?

The switch only controls a soffit light above the kitchen sink.

So seeing this picture now, can anyone tell me how to ground the dishwasher?

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Old 01-06-16, 09:23 AM
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I'm sorry but I can't. I don't see a ground wire at the switch and from the picture I can't tell if your house is wired with cable or conduit. Which is it, cable or conduit? Does the box seem to have three or four pipes coming in with nuts on them? A picture of your breaker box with the cover removed will help also. WE need to see the whole box and about an inch of wall all around.

Is there a bare wire connected to the ground of the GFCI receptacle? I can't see.
 
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Old 01-06-16, 09:27 AM
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Flexible conduit can not serve as a ground unless it has a bonding strip
Ray can correct me if needed. Why don't you just run an approved flex line from the box into the sink base cabinet, install a box and receptacle, and be done with it?
Attach a cord to the DW.
If you do end up hardwiring the DW, most new units have absolutely no room to work below. It's a little challenging and the time it takes to add a receptacle is worth it.
 
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Old 01-06-16, 09:31 AM
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Why don't you just run an approved flex line from the box into the sink base cabinet, install a box and receptacle, and be done with it?
Yes, but this may be an old ungrounded cable system with no ground.
 
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Old 01-06-16, 09:38 AM
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Just opened breaker box. Box has rigid conduit coming into it from above.

Running a whole new line is not really an option as the basement is entirely enclosed in tongue and groove pine paneling. There's really no way to access the walls to run a new line.

Light switch box above dishwasher has 5 lines running into it. I'm assuming all rigid conduit as that's what I see above the breaker box in basement.

I do not see a bare ground wire on the GFCI outlet. Only white and black wires.

Also, for reference - previous dishwasher was ungrounded (i'm assuming) because only the white and red wires from wall were attached to the dishwasher. It was like this for about 10 years with no issues. Not sure if that makes a difference.

Pictures to come as soon as my computer stops acting stupid.
 
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Old 01-06-16, 09:44 AM
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If it is rigid conduit to the switch box just run a green ground wire from a ground screw in the switch box through the Greenfield to the dishwasher space and run the Greenfield into the cabinet next to the DW. Install your GFCI receptacle for the DW there.
 
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Old 01-06-16, 09:53 AM
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Here are the photos. I will try and see if I can confirm that there is rigid conduit going to the switch box.

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Old 01-06-16, 09:57 AM
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By ground screw you just mean a self tapper right into the box itself?

Also what amp GFCI should I put under the sink?
 
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Old 01-06-16, 10:03 AM
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By ground screw you just mean a self tapper right into the box itself?
Yes, 10-32 machine screw (not a sheet metal screw).
what amp GFCI should I put under the sink?
A 15 amp is okay even if it is a 20 amp circuit.
 
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Old 01-06-16, 01:57 PM
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Thank you so much for all of the help gentleman, the dishwasher is now installed and working perfectly!
 
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Old 01-06-16, 03:39 PM
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!EXCELENT! Thanks for letting us know.
 
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Old 01-06-16, 08:12 PM
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The receptacle should not be behind the DW. It can be in the sink cabinet. It would also need gfi protection under the 2014 code.
I am not really familiar with the 2014 code, but I think it requires the dishwasher to also be AFCI protected. I believe this was one of the reasons the dual function GFCI/AFCI circuit breakers were developed.
 
 

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