Water Heater connection flamed out!


Old 06-14-11, 08:33 PM
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Water Heater connection flamed out!

Hello all,
OK, I'll start with the questions first so the professionals (who probably see this every day) won't need to read the story...

First, what's the proper way to connect 10 ga. solid to stranded? I used a wire nut and apparently didn't do it correctly. Is there something better than a wire nut? I seem to remember a small "Bug" type connector with a "wire nut top" that threaded over it. How about a crimp ring?
Does the NM dropping down from the joist to the water heater need to be in pipe? I've seen with and without.
If the NM does go into a pipe, does the jacket need to be stripped so just the wires are in the pipe? I've been told that it does, but the current installation has NM going right into EMT at the joist. Also, the way I read the code, it sounds OK (see 334.15(B).
Thanks in advance for your suggestions.

and now a cautionary DIY tale - I had done some electrical work next to the water heater a couple of weeks ago (unrelated to problem). I thought I smelled something overheating, like burning plastic. Couldn't find the source, so I didn't pat much attention. So last Sunday, I come in from working in the yard all day. Go to take a shower and there's no hot water. "[email protected]#$% cheap Lowe's water heater!" I'm thinking. I go downstairs to find a large burned area on the top of the palstic control box on the water heater! Opened it up and found one of the Hot lines had flamed out! The wirenut was completly consumed - only stubs of the wings were left and insulation on the failed connection had burned back about 4 inches. The hot line had finally burned off enough of the insulation to come in contact with the ground and trip the breaker.
I dodged the bullet on this one. If this had happened in a wall, it could have easily caused a fire. Be careful...

Thanks again for your comments and suggestions,
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Old 06-15-11, 05:30 AM
pcboss's Avatar
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A properly sized wire nut should be fine for your connection. Lead the stranded slightly past the solid and then twist. Give a slight tug on the stranded to make sure it is secure.

Do not strip the outer jacket off the cable in the conduit sleeve. Unless subject to physical damage you probably don't need the EMT, but it does make it look neater. You should have a bushing at the ends to prevent abrasion on the insulation.
Old 06-15-11, 05:17 PM
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We always sleeve our NM cable feeding water heaters with a short piece of FMC. Looks professional and protects the cable.
Old 06-15-11, 09:11 PM
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Our nm is usually taped or ty-raped to the cold water pipe, although I would rather see conduit.

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