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    stanfortyman's Avatar
    stanfortyman Posts: 5,598, Reputation: 279
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    #21

    Feb 20, 2008, 02:36 PM
    Quote Originally Posted by tkrussell
    For a home with an existing 2 wire cable with ground, the bare is allowed to be used as the neutral and equipment ground per this exception.
    This is ONLY allowable if the existing cable is type SE. The bare wire in NM cable is not, and NEVER was, allowed to carry regular circuit current. PERIOD.
    Frankly I am surprised that anyone is even suggesting it can.

    Here is the applicable code section:

    250.140 Frames of Ranges and Clothes Dryers

    Frames of electric ranges, wall-mounted ovens, counter-mounted cooking units, clothes dryers, and outlet or junction boxes that are part of the circuit for these appliances shall be grounded in the manner specified by 250.134 or 250.138.

    Exception: For existing branch circuit installations only where an equipment grounding conductor is not present in the outlet or junction box, the frames of electric ranges, wall-mounted ovens, counter-mounted cooking units, clothes dryers, and outlet or junction boxes that are part of the circuit for these appliances shall be permitted to be grounded to the grounded circuit conductor if all the following conditions are met.

    (1) The supply circuit is 120/240-volt, single-phase, 3-wire; or 208Y/120-volt derived from a 3-phase, 4-wire, wye-connected system.

    (2) The grounded conductor is not smaller than 10 AWG copper or 8 AWG aluminum.

    (3) The grounded conductor is insulated, or the grounded conductor is uninsulated and part of a Type SE service-entrance cable and the branch circuit originates at the service equipment.

    (4) Grounding contacts of receptacles furnished as part of the equipment are bonded to the equipment.




    See, the exception is that the grounded conductor could also be used as the grounding conductor. NOT the other way around.
    A NEUTRAL WAS ALWAYS REQUIRED!
    donf's Avatar
    donf Posts: 5,679, Reputation: 582
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    #22

    Feb 20, 2008, 02:54 PM
    Standforty man,

    Well I'm in serious trouble, because my place has a three wire drop and three wires com into the SEP. Two are Hot and one goes to the Neutral bus. On the neutral bus, both ground and neutrals are connected. Physically, there is no grounding bus in the SEP.

    So I have only two hots and a Neutral, The house is currently receiving a 200 amp service. Now I know the at the SD panel, ground and neutral meet up. So I understand the wisdom of using the neutral bus for both ground and neutral connections. What I don't understand is how two electricians can read the same code cite and come up with two different answers both supported by the same text in the book. Sorry, that makes no sense to me.

    Is there a method in place to get the NEC to explain what the paragraph is actually saying>
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    stanfortyman Posts: 5,598, Reputation: 279
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    #23

    Feb 20, 2008, 03:05 PM
    Sorry Don. I am not following you.
    How does this apply to the topic at hand? Meaning a household cooking appliance.
    stanfortyman's Avatar
    stanfortyman Posts: 5,598, Reputation: 279
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    #24

    Feb 20, 2008, 03:28 PM
    Quote Originally Posted by donf
    Is there a method in place to get the NEC to explain what the paragraph is actually saying>
    The NEC Handbook is a BIG help in this respect.
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    tkrussell Posts: 9,659, Reputation: 725
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    #25

    Feb 20, 2008, 04:19 PM
    Excellent, someone reads the exceptions to the exception.

    Now the poster has a very clear answer.

    Nicely done, Stan.
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    qn1234 Posts: 15, Reputation: 1
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    #26

    Feb 20, 2008, 08:42 PM
    Before I go any further with this question, please tell me what wires you have coming from the breaker to the receptacle. Are they Black, Red, White and bare or are they Black, White and bare ground?
    Currently, it's a 12/2 wg (3-wires: black, white, and bare) NM cable. It's hooked up to a standard white 3-leg receptacle like the ones around the house. The old 24" microwave has a standard 3-leg plug like the one from a carpet vacuum. Had my wife wanted a 24" or 27" microwave there wouldn't be a problem. Hey, but I don't blame her; she wants something to match with the rest of other appliances.

    I was aware of the voltage difference, but I was told it's going to be an easy job. :confused:
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    qn1234 Posts: 15, Reputation: 1
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    #27

    Feb 20, 2008, 08:55 PM
    Quote Originally Posted by stanfortyman
    This is ONLY allowable if the existing cable is type SE. The bare wire in NM cable is not, and NEVER was, allowed to carry regular circuit current. PERIOD.
    Frankly I am surprised that anyone is even suggesting it can.

    Here is the applicable code section:

    250.140 Frames of Ranges and Clothes Dryers

    Frames of electric ranges, wall-mounted ovens, counter-mounted cooking units, clothes dryers, and outlet or junction boxes that are part of the circuit for these appliances shall be grounded in the manner specified by 250.134 or 250.138.

    Exception: For existing branch circuit installations only where an equipment grounding conductor is not present in the outlet or junction box, the frames of electric ranges, wall-mounted ovens, counter-mounted cooking units, clothes dryers, and outlet or junction boxes that are part of the circuit for these appliances shall be permitted to be grounded to the grounded circuit conductor if all the following conditions are met.

    (1) The supply circuit is 120/240-volt, single-phase, 3-wire; or 208Y/120-volt derived from a 3-phase, 4-wire, wye-connected system.

    (2) The grounded conductor is not smaller than 10 AWG copper or 8 AWG aluminum.

    (3) The grounded conductor is insulated, or the grounded conductor is uninsulated and part of a Type SE service-entrance cable and the branch circuit originates at the service equipment.

    (4) Grounding contacts of receptacles furnished as part of the equipment are bonded to the equipment.




    See, the exception is that the grounded conductor could also be used as the grounding conductor. NOT the other way around.
    A NEUTRAL WAS ALWAYS REQUIRED!
    :confused: I'm totally confused now! :confused:

    First, there was hope, then little hope, then some hope, and it now looks like I'm going to have to bring out the hammer and knock down some walls. :o I've been staring at the walls and scratching my head. :confused:
    stanfortyman's Avatar
    stanfortyman Posts: 5,598, Reputation: 279
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    #28

    Feb 20, 2008, 09:43 PM
    Quote Originally Posted by qn1234
    :confused: I'm totally confused now! :confused:
    Really? I had hoped it was very clear.
    What are you unsure about?
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    qn1234 Posts: 15, Reputation: 1
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    #29

    Feb 20, 2008, 11:45 PM
    Quote Originally Posted by stanfortyman
    Really? I had hoped it was very clear.
    What are you unsure about?
    I didn't mean to say that your posts were not clear. I think they are very helpful and make a lot of sense. It's me who lacks of knowledge about electrical wiring. After reading posts from various people I'm confused as to whether I will end up tearing down the walls, sale the unit and buy something else, or hire an electrician to do the work. I'm an average DIYer and I like to do it myself if it's feasible.

    We spent some $1500 on this unit and hate to sale it at a loss. I'm afraid Sears might not want to take it back since we have it for a month now. Anyway, we rather keep this unit.

    I really appreciate your and others' help.

    Please keep talking. Maybe there is still a better answer out there.
    donf's Avatar
    donf Posts: 5,679, Reputation: 582
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    #30

    Feb 21, 2008, 06:08 AM
    Well for one thing, Sears has a 30 day, free return policy. That solves the problem for you one way.

    However, why are you thinking that you need to knock walls down? When I had to change the conductors from 10/3 to 8/3 for a new range/oven @ 40 amp, all I had to do was get my hand inside the wall and pull the two staples out, then I attached a "Chinese finger" onto the end of the 10/3 and used the existing 8/3 to pull the new wire down to the SEP.

    Now I only had to pull about 20' of cable, so it went quite smoothly. However if you are the least bit unsure of what you have to do in the SEP, then under no circumstances should you attempt to do the work. You can do all the prep work, for example pulling the cable, than call the electrician to do the connections and test the work,

    Regardless, though of who does the work, someone will have to get an electrical permit. Home owners can get permits, however, If I'm hiring someone to do the work for me, I would want him to do the entire job which would include pulling the new conductors and getting both the permit and the required electrical inspection.
    Stratmando's Avatar
    Stratmando Posts: 11,188, Reputation: 508
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    #31

    Feb 21, 2008, 06:35 AM
    Hook up the Black to breaker, Identify white as red or black, connect to Breaker, Neutral and ground to ground. You should already be cooking. Don't let it all get confusing. Use the Metal plate with Greenfield connector, and call it a day.
    donf's Avatar
    donf Posts: 5,679, Reputation: 582
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    #32

    Feb 21, 2008, 07:54 AM
    "Sorry Don. I am not following you.
    How does this apply to the topic at hand? Meaning a household cooking appliance."

    Okay, I only have three populated lugs on my SEP. They are two hots and one Neutral. The Neutral Bus Bar is populated by both Bare and White wires.


    There is no way for me to attach a bare wire to Ground, because there is not a physical Ground bus bar. If I were to replace the conductors with a 12/3 line to the oven's receptacle, I would have to attach both the White and the Bare wire to the Neutral bus, correct?


    With respect to the existing 12/2 conductors, what difference does it make whether I use White or Bare for ground, they are both connected at the same connection point. While White can carry current, (as in a 120/20 amp switch loop circuit) what stops ground from doing the same? Ground will have to carry short circuit current safely to a ground rod and isn't a short circuit capable of a very large amperage rate even if for a very short, no pun intended, duration? Is your thinking directed at the size of the 12/2 Bare wire? Because the bare wire is insulated within the cable sheathing, is it not?


    Why this in important to me, because I'm playing catch-up with re-learning the NEC code and implementing the current code to update some horrible electrical work that was a gift from a previous owner. I'm working very hard at learning. I haven't had to study basic electricity since 1972. From then on it was all electronic work both in the field and in labs.

    If I've got something wrong because I remembered incorrectly then I've got two problems. One the work I did was incorrect and has to be done properly and two, the electrical inspector that approved what I did, needs to be re-educated.
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    qn1234 Posts: 15, Reputation: 1
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    #33

    Feb 21, 2008, 08:48 AM
    Quote Originally Posted by Stratmando
    Hook up the Black to breaker, Identify white as red or black, connect to Breaker, Neutral and ground to ground. You should already be cooking. Don't let it all get confusing. Use the Metal plate with Greenfield connector, and call it a day.
    Somehow I feel this is going to work, but this is what others suggested not to do. :o

    Anyhow, before doing anything, I'm going to call in a licensed electrician, have him explain what's involved. I go get a permit, then have him do the wiring. I'm familiar with the permit process as I have done my garage to game room conversion last year.

    Worst case, I can see that by cutting four 5"x5" holes on the ceiling I should be able to run a new 10/3 gw cable from microwave to the subpanel sitting under the stairway. The distance is about 20 feet. I installed some recessed lights before on the same ceiling so I'm familiar with running cables across the joists.
    donf's Avatar
    donf Posts: 5,679, Reputation: 582
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    #34

    Feb 21, 2008, 10:22 AM
    Quote Originally Posted by qn1234
    Somehow I feel this is going to work, but this is what others suggested not to do. :o

    Anyhow, before doing anything, I'm going to call in a licensed electrician, have him explain what's involved. I go get a permit, then have him do the wiring. I'm familiar with the permit process as I have done my garage to game room conversion last year.

    Worst case, I can see that by cutting four 5"x5" holes on the ceiling I should be able to run a new 10/3 gw cable from microwave to the subpanel sitting under the stairway. The distance is about 20 feet. I installed some recessed lights before on the same ceiling so I'm familiar with running cables across the joists.
    Quang,

    Do not get the permit yourself! If you are calling in an electrician to do the work, let him submit the required plan and obtain the permit. If you get the permit yourself, then you are going to be held responsible for any mistakes the electrician made during the inspection, not the electrician.

    If the electrician pulls the permit, then he is responsible to repair any mistakes he made, not you.

    That's the way it works here in Virginia. Only a home owner or a Master electrician can pull permits with the appropriate forms and a drawing of the proposed work.
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    qn1234 Posts: 15, Reputation: 1
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    #35

    Feb 21, 2008, 11:22 AM
    Quote Originally Posted by donf
    Quang,

    Do not get the permit yourself! If you are calling in an electrician to do the work, let him submit the required plan and obtain the permit. If you get the permit yourself, then you are going to be held responsible for any mistakes the electrician made during the inspection, not the electrician.

    If the electrician pulls the permit, then he is responsible to repair any mistakes he made, not you.

    That's the way it works here in Virginia. Only a home owner or a Master electrician can pull permits with the appropriate forms and a drawing of the proposed work.
    Good suggestion. I will keep that in mind.

    I do appreciate your and others' help. This is a wonderful forum.
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    donf Posts: 5,679, Reputation: 582
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    #36

    Feb 21, 2008, 11:39 AM
    Stanforty,

    Light bulb on, 2X4 across the top of my head! By Jove I think I now understand your issue with the cable.

    I re-read your previous posts and just now picked up on why neutral is needed.

    It is because the appliance needs both 120 and 240VAC correct? Therefore I also need to supply a Neutral and a ground.

    But I have no way of supplying a ground because I have only three wires on the Service Drop. Two Hot, 1 Neutral. My only choice, if I follow your instructions correctly, is to wire both Neutral and Ground to my Neutral Bus bar.

    Why the commotion if I do it as I originally suggested? The only difference would be the bare wire serving a neutral as to the installation, the nm cable does shield the bare wire.

    These are questions, I'm hung up on the understanding why, since in both cases you would be getting 120/240 to the receptacle. Which by the way, I haven't found an outlet rated at 120/240 20 amp. Do they even make them or would Mr. Quang have to use a 30 amp outlet which would force him to rewire with 10/3 AWG and a 30 amp breaker.

    Believe me I'm not trying to be a pest, I am trying to understand your logic over mine.
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    qn1234 Posts: 15, Reputation: 1
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    #37

    Feb 21, 2008, 01:07 PM
    Quote Originally Posted by donf
    Stanforty,

    Light bulb on, 2X4 across the top of my head! By Jove I think I now understand your issue with the cable.

    I re-read your previous posts and just now picked up on why neutral is needed.

    It is because the appliance needs both 120 and 240VAC correct? Therefore I also need to supply a Neutral and a ground.

    But I have no way of supplying a ground because I have only three wires on the Service Drop. Two Hot, 1 Neutral. My only choice, if I follow your instructions correctly, is to wire both Neutral and Ground to my Neutral Bus bar.

    Why the commotion if I do it as I originally suggested? The only difference would be the bare wire serving a neutral as to the installation, the nm cable does shield the bare wire.

    These are questions, I'm hung up on the understanding why, since in both cases you would be getting 120/240 to the receptacle. Which by the way, I haven't found an outlet rated at 120/240 20 amp. Do they even make them or would Mr. Quang have to use a 30 amp outlet which would force him to rewire with 10/3 AWG and a 30 amp breaker.

    Believe me I'm not trying to be a pest, I am trying to understand your logic over mine.
    Okay, this brings up a question... again.

    Given that have a 12/2 wg, can I use the bare for neutral and share the ground off the oven sitting right below the microwave? I know I asked this in the original post.

    Note that there is an oven using 10/3 wg right below where the microwave goes.
    donf's Avatar
    donf Posts: 5,679, Reputation: 582
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    #38

    Feb 21, 2008, 01:21 PM
    No,

    Look at the installation instructions, they are tying Neutral to ground on the appliance. You would be using the bare wire as both neutral and return.

    By the way, Are you sure that your home is on a three wire drop or lateral? How do you know this for sure, have you been inside the main panel and verified that there are two power lugs and only one Neutral wire and bus bar?

    If you actually have four wire, then your only option is to remove the 12/2 and run 12/3 and all this dialogue, while very interesting, particularly to me, would become pointless.
    stanfortyman's Avatar
    stanfortyman Posts: 5,598, Reputation: 279
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    #39

    Feb 21, 2008, 01:41 PM
    Quote Originally Posted by Stratmando
    Hook up the Black to breaker, Identify white as red or black, connect to Breaker, Neutral and ground to ground. You should already be cooking. Don't let it all get confusing. Use the Metal plate with Greenfield connector, and call it a day.
    This is 100% flat out WRONG.
    Do whatever you want, but this is WRONG.

    Telling someone to use the bare ground of an NM cable as a current carrying neutral is NOT a very smart thing to do. If something bad happens because of this, and this is quite possible, where will you be??

    To QN. The information I have given you is code correct. I have provided facts to back it up. Whether you follow this or other information is up to you.

    Good luck.
    stanfortyman's Avatar
    stanfortyman Posts: 5,598, Reputation: 279
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    #40

    Feb 21, 2008, 01:54 PM
    OK Don, I'll try to explain the best I can.

    The three wires coming into your house are indeed two hots and what is correctly called the grounded conductor. The layman's term for the grounded conductor is "neutral".
    There is NO "grounding" conductor coming in from the utility. You will never have a "4-wire" drop from the street. The POCO will never provide a grounding conductor.

    A "grounded conductor" is one that is intentionally grounded at some point. This is the conductor that carries the current imbalance of the two hot service wires. This is also what gives us 120 volts at our service instead of just 240v.

    A grounding conductor, or more correctly, "equipment grounding conductor" is NOT the same thing. Here is a definition:

    Grounding Conductor, Equipment. The conductor used to connect the non–current-carrying metal parts of equipment, raceways, and other enclosures to the system grounded conductor, the grounding electrode conductor, or both, at the service equipment or at the source of a separately derived system.




    At the main service disconnect the two are bonded, meaning they are connected together mechanically and electrically. This is the ONLY Place that they are bonded.

    A bond neutral to ground bond downstream of the service equipment can be a very dangerous thing. Metal parts of equipment can become energized. Connections can arc and spark. Splices and connections can become hot to the point of fire.
    If they are bonded, or if the ground is used as a neutral, the grounding can and will carry current. THIS is what makes it dangerous.
    An equipment grounding conductor is NOT meant to carry current.

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