DW Wiring

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  #1  
Old 06-08-07, 07:09 AM
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DW Wiring

Last night my daughter's DW quit working. She asked me to look at it. It appeared to have no power. The breaker was not tripped. The DW is hardwired to a 20Amp circuit.

When I checked the power connection in the JBox I was surprised. The ground screw was a chunk of corrosion. Although the connection was still made, it was so corroded that I wonder how good the ground was. The inside of the wire nuts were also corroded. There were arc strikes in a couple of spots in the JBox. I fixed the leak, and remade the connections with new wire nuts and ground screw.

My questions concerns the breaker. I am concerned that if this happens again, the potential is there for a dangerous shock. Would a GFI breaker protect the user from a shock if the JBox gets wet again? Is there a reason why a GFI breaker isn't required on this circuit? Is there a reason why I can't install a GFI breaker even if not required?
 
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Old 06-08-07, 07:33 AM
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The underside of dishwashers sometimes turn in to a pile of rust because of small leaks that develop.

A bad grounding connection will not cause the dishwasher to stop working. You didn't say whether or not the dishwasher now works or what you did to make it work. I'm curious about that.

You are correct to worry about shocks. A GFCI breaker on a dishwasher is unusual, but not prohibited and it would substantially increase safety. GFCI is not required because in general the electrical code assumes that well-maintained appliances don't leak.

Go ahead and replace the breaker with a GFCI breaker (or, if the dishwasher is cord-and-plug connected, use a GFCI receptacle). It might occasionally trip when it shouldn't, but that's a small price to pay for increased safety.

Consider a new dishwasher. They don't last forever, and this one may be on its last legs.
 
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Old 06-08-07, 09:02 AM
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John - Thanks for the response. The operating problem wasn't the ground, but the hot connection in the junction box. The corroded ground connection concerned me as a safety issue. I'm not an electrician, but I suspect a rust ball isn't an ideal connection. The wire nuts inside the jbox were also corroded and loose. It looked like most of the internal threads on the nuts were rotted. I put a magnet up to a couple of new wire nuts and was surprised to see that they are ferrous. IMO the connection was poorly made on install. Both black and white wires were only loosely twisted together. There were a couple of black spots on the inside of the jbox that looked like arc strikes. My guess is that when the connections got wet enough, they shorted intermittantly and the DW would quit.

The DW is only 4 years old. I remade the connections, taped the wire nuts thinking that might make them water resistant. I also taped the seams of the junction box in case it developes another leak. It now works fine. I ran it through a couple of cycles to check for leaks. There were none.

I'm headed over to her house to replace the breaker with a GFI. That's easier (and probably cheaper) than installing a cord and GFI receptacle. I just wanted to make sure I wasn't going to create another problem.
 
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Old 06-08-07, 10:22 AM
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Usually when I wire something in an area that could get wet, I try to bend the wires to orient the wirenuts inside the junction box such that they open downwards and cannot collect water. Make them "hats" instead of "cups".

> The breaker was not tripped.

For my own curiosity, what was the brand and approximate age of the breaker?

> the potential is there for a dangerous shock. Would a GFI breaker protect
> the user from a shock if the JBox gets wet again?

Yes and yes.

> Is there a reason why a GFI breaker isn't required on this circuit?

Usually, a properly grounded dishwasher will trip the breaker if there are any ground faults. Furthermore, the user-accessible parts of a dishwasher are plastic so even if the frame is energized, the user shouldn't be at risk.

> Is there a reason why I can't install a GFI breaker even if not required?

No, you may add one if you so choose.
 
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Old 06-08-07, 11:33 AM
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A little more info - The DW was installed by the appliance store. I don't know if they are required to be electricians but from what I saw the guy that made up this connection wasn't very skilled.

The breaker was a Murray 20A. I think it's probably OK but I'm putting in a GFI. I believe from the looks of the connections that the shorts were intermittant and the reason it quit working was because the corroded/loose connections actually opened. The hot and neutral wires had only a couple of loose twists. I think the wire nuts got wet and corroded allowing the poorly twisted wires to loosen.

I really wish I had taken a couple of pictures.
 
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