Adding OTR Microwave Circuit

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rowdy235

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Hey guys, hope everybody is doing well in this crazy time. I have been trying to get some home improvement done and had a question about a new project I'm working on.

The house I am in is 50's era and had the wiring upgraded at some point (in the 70s) but it still lacking compared to modern standards. I only have a 100a panel and right now most of the outlets are all on one 20a branch circuit. Obviously the "heavy hitter" appliances test that limit. Eventually I'm planning to have the house rewired and upgraded to a modern 200a service, but that's a ways down the road.

For now I picked up an over the range microwave on a good sale and I'm looking to get a new circuit run for it. Fortunately, I freed up a 240v 20a circuit last year by replacing the (original!) electric W/H with a gas model. The wire that used to feed the W/H comes out of the wall in a finished utility room right on the other side of the wall where the OTR Microwave will be going, but down at waist level.

To be clear, I am planning to have an electrician come out and make the connections, but just wanted to get thoughts on my plan.

My plan was to replace the existing 240v breaker for the water heater with 2 120v 20a breakers, one for the microwave and one for future expansion. I would then use one of the existing hot 240v wires for neutral and the other for hot, and still have a ground, essentially converting the 240v circuit into a 120v. (Wire is 10ga IIRC)

Now, the other issue is that the wall between the kitchen and utility room is insulated, and lath/plaster on both sides. So fishing a new wire up to above the microwave is not really a viable option. Would running some EMT from a junction box on the utility room side where the existing wire comes out of the wall, running up and going through the wall and into the kitchen cabinet on the other side to a surface mount box be a safe/code complaint option? I've read so many opinions and code references but all I can come up with is "nothing says it isn't legal".

I appreciate any feedback, thanks in advance!
 

Stuff

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Verify the old cable has a full size ground. Assume one wire is white. Rest of the plan sounds OK.

Code tells you what you can't do. It isn't a design guide so you have a lot of leeway.
 
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MWr

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According to your plan, everything should work without problems.
 

rowdy235

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Thanks for the replies!

After further inspection yesterday it appears the circuit does not have a ground after all- only two hots and neutral, red, black, and white wire. So it doesn't look like there's any code-complaint way to make that circuit work. Probably better to run a circuit with some modern wire anyway, and at least I have good crawlspace access.

Thanks again!
 

jadnashua

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10g wire is kind of a bear to fish anywhere. But, if you were able to use that cable, if it isn't long enough, keep in mind that any splice needs to be in an electrical box. If you identified say the red wire as ground, it would work.

THey make flexible, 5' long drill bits, and, you can buy an extension for them as well. You need to have a good idea what's in the wall so you don't inadvertently drill through say a gas line, water, or drain, or another wire, but that can let you get a hole where you need it to run your wire. They have a small hole on the end you can then attach the new wire to and pull it back, or you could pull some string, and then use that to pull your wires.

Even on plaster, if you cut out a small section, I've been able to put it back in, patch the saw kerf, and repaint, making that look as good as new. You can use EMT, as far as I know. It's nicer to have it in the wall, though.
 

rowdy235

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Running inside the wall would obviously be preferred, but just not sure of the feasibility. The back side of the wall is just a utility room so I'm not concerned about the EMT looking bad or anything. My plan was to install a junction box where the existing wire exits the wall, run EMT up the wall and through to the other side, to a surface mount box inside the cabinet. From there I would pull some THHN through the conduit and splice to the existing wire.

However it is my understanding that you cannot (per code anyway) relabel/recolor a wire to be a ground. While I'm sure it would work fine (heck, most of the house is 2 prong outlets anyhow) if I sell this house I don't want it to pop up on an inspection and have to run a new circuit anyway.
 
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