replace 220v oven with 115v microwave

Discussion in 'The Projects Forum' started by Bork2, Feb 14, 2015.

  1. Bork2

    Thread Starter New Member

    Feb 14, 2015
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    I want to remove a 220v wall oven and install a 115v microwave in same area. Its a built in oven and I think its directly wired rather than use of a receptacle. Wires connected in a metal box that just sits behind the oven. Probably some kind of pigtail to also give 115v to electronics, clock, etc. Need to install a 115v receptacle for the MW. The current circuit is from a breaker (2-pole?) in my main outside box. I assume this is a 20 amp circuit now. Can I use the existing breaker or need to replace it with 15 amp single pole? Any help/ideas before I start this project would be appreciated.
     
  2. Dodgydave

    AAC Fanatic!

    Jun 22, 2012
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    What country are you in?
     
  3. Bork2

    Thread Starter New Member

    Feb 14, 2015
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    US Florida
     
  4. MaxHeadRoom

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    Jul 18, 2013
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    If it is 240v and neutral, use one conductor (L1) and neutral and cap off the other (L2).
    Ensure the wire size is sufficient, and you can replace the relevant double breaker with a single 15amp if you wish, you could also remove and cap off the unused L2.
    Fit a 15amp outlet. Make sure you also have a ground wire.
    You could also cut the link on the Live side of the outlet and use L1 & L2 for each top and bottom outlet, replace the breakers with two separate 15amp.
    Max.
     
  5. #12

    Expert

    Nov 30, 2010
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    1) Don't assume what size the breakers are, read the label.
    You have to turn them off to change the wiring. That is a good time to read the label.

    2) What colors of wires are arriving at the metal box?
    Especially, is there a red in there?
     
  6. MaxHeadRoom

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  7. Reloadron

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    Jan 15, 2015
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    What you should have is 240 VAC split phase and coming from the breaker box should resemble the below drawing if it was installed correctly.

    240 VAC Split.png

    Depending on the breakers the wire gauge should be AWG 14 (15 Amp Service) or AWG 12 (20 Amp service). The color scheme should look like the drawing. The breakers should be "ganged" and mechanically tied together so if either breaker trips it takes the other with it. Both breakers (or at least one) should be replaced. For kitchen counter application and a microwave oven you want a single line of AWG 12 for a 20 Amp service outlet. All kitchen service outlets should be GFIC protected either using a GFIC breaker at the panel or a GFIC outlet. I suggest you check the name plate data on the microwave oven and note the wattage?

    If the existing branch line is AWG 12 wire then just fold the red back and disconnect the red at the breaker panel and only use the white and black. Service outlets are polarized. The outlet should look like this:

    120V 20A Outlet.png

    That is a rough approximation.

    Ron
     
  8. #12

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    I often enough find this:
     
  9. #12

    Expert

    Nov 30, 2010
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    Then you have to change it to this and use a 20 Amp receptical.
     
  10. Reloadron

    Active Member

    Jan 15, 2015
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    Yeah, should have included the new 120V. My excuse is I wanted to eat dinner so I rushed things. :)

    120 Volt.png

    I love the eraser tool.

    Ron
     
  11. #12

    Expert

    Nov 30, 2010
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    Sorry. I missed that one. :oops:
     
  12. Bork2

    Thread Starter New Member

    Feb 14, 2015
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    Thanx Ron, et al. Remember I'm just a rookie DIY so even your diagrams I have to deal with. So, can I just remove the current breaker, replace it with a single pole 15amp one and use the existing 12 guage wire to a new recepticle? I'll soon get around to taking the oven out and giving you feed back on what is there.

    Bob
     
  13. Reloadron

    Active Member

    Jan 15, 2015
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    Yes, but I would check and see what the existing wire gauge is. Here is what I will share with you. There is the NEC (National Electric Code) and there are also State and Local building codes that govern this sort of stuff. I would be remiss if I didn't tell you how this should be done to code. What you will have is a counter top kitchen appliance. While I do not know the power requirements of your specific microwave oven the NEC does spell out kitchen outlets. NEC Article 210, Section III covers required outlets. Nowhere does it specify that a microwave has to have a dedicated circuit. The microwave is just another cord/plug kitchen appliance. The required circuitry for that is covered in Article 210.52 (B) and (C). All said and done I believe in all of that without reading deeper that there is a requirement for 20 Amp service and it must be GFIC. I know a 20 Amp GFIC Circuit Breaker (New ones combine AFCI/GFCI) run around $40 each rated for 20 Amp service which is the code. There is also the option of using GFCI outlets rather than a GFCI feed from the breaker panel.

    How you choose to go about doing this work is your choice, I am saying you should research your local codes which are generally based on the NEC. Many residential communities have their additional codes and require the work be done by a licensed and bonded electrician and be inspected upon completion. Many locals require a local city building permit be pulled before starting the work, so again the research rest with you.

    That said if it were me I would run 20 amp service using AWG 12 wire and wire to code. For kitchen counter appliances I would make sure there was GFCI protection.

    Ron
     
  14. MaxHeadRoom

    Expert

    Jul 18, 2013
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    If you have a 12g supply there you are half way home, check the rating of the M.W.
    You can also either replace the breakers with singles or in some cases the bridge link can be removed on the double.

    From the previous Link.
    "The new code now requires all kitchen receptacles to be protected by ground fault circuit interrupter (GFCI) receptacles, and must have at least two 20A circuits supplying general purpose kitchen receptacles."
    Max.
     
  15. Bork2

    Thread Starter New Member

    Feb 14, 2015
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    Well----In my box I have a 30 amp 2 pole breaker for the current oven. There is a red and black wire--one at each pole. The cable also has a white wire and it connects to the common bar in the box. These are 10 gage wire! The microwave requires at least 20 amp circuit. It is not a counter top but a shelf mounted appliance. So--whats best way to go about this now. Is there a receptacle that easily handles the 10 gage size?
     
  16. #12

    Expert

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    It's never easy to wind a 10 ga wire around a screw, but have you tried?
    If all else fails, you are allowed to wire nut on a piece of 12 ga wire.
    There is no such thing as a 30 amp 120V receptical. You should buy a 20 amp receptical and a 20 amp breaker, then look at post #7
     
  17. Reloadron

    Active Member

    Jan 15, 2015
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    Actually #12 there is a 30 Amp 120V service receptical and plug. NEMA L5-30. The terminals are made to handle #10 AWG without busting up your fingers. Just for future reference.

    Ron
     
  18. #12

    Expert

    Nov 30, 2010
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    Ah...the twist-locks. I did not consider those for residential use, but they will work.
    NEC has some strange rules about how many 15A or 20A outlets MUST be attached to a 20 A breaker.
    Any strange rules about 30 amp circuits?
     
  19. Reloadron

    Active Member

    Jan 15, 2015
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    Ah yes, the NEC book is a fun book. A real treat to follow. When I retired I should have burned those books but decided to take them with me. Every 3 years we were required to take the course in my engineering department. On the bright side it got us out of the plant for a week. :) One of the greatest days of my life was the day our department hired an IE (Industrial Engineer) because I was forever getting sucked into IE projects I had little to absolutely no working knowledge of.

    As to 30 Amp 120 Volt circuits? Really nothing strange in the NEC I see at a glance. A 20 amp breaker branch circuit must be 12 AWG and a maximum of 14 taps. A 30 amp breaker branch circuit must be 10 AWG and a maximum of 14 taps. Table 210.24 Summary of Branch-Circuit Requirements. Also, I agree that in residential you seldom if ever see a 120 volt 30 amp service twist lock plug and receptical. I never have anyway but such weird things do exist.

    We had a guy at the plant once manage to get caught on a power cord that should have been below the deck and yank it out of the wall. Great, an OSHA trip hazard plus when the test stand lost power some incredibly bad things happened. When bad things happen there are forms and forms to complete. Then more forms and then meeting to explain what went wrong and why it went wrong. Following that incident I had every single critical outlet become a twist lock. Yep, I was a real happy person the day we hired Chuck the IE. :)

    Ron
     
  20. #12

    Expert

    Nov 30, 2010
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    Every three years? What's the big deal? I read the 1981 NEC book once and figured out what the inspector would want to see. (NFPA 70-1981) After that it was a rare event that I got caught doing something wrong...like 2 wires under a screw clamp. Odd, that's how the neutrals are done in the breaker box. Why can't I do that with the power wires?

    It doesn't matter. The only thing that matters is getting the inspector to sign off. :D
     
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