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  • 4 vs 3 conductor plugs for kitchen ranges

    Picked up a craig's list range to replace the ratty one I had. Replacement came with a 4 prong plug. Wall had a 3 prong socket. There was a ground wire in the box not attached to anything, so I went and got the 4 connector socket and wired it in and all seems well.

    My question is why? I felt it would be a little reckless to do but suspect it would have worked just fine to wire the 3 connector cord from the old range into the new one. Can you do this and just jumper the ground to the neutral? what consequences are you risking if you do? is it better to leave the ground unconnected or to jumper it to the neutral? Or is it just crazy unsafe and pull another wire if you only have 3? and if so, why?

    I'm confused in general about the difference between a ground and a neutral since they are (at least in the very few boxes I've had the front off of) connected together at the box anyway. Doesn't this make them the same wire?

    Can anyone explain?

    also, just for my peace of mind, have I done something unsafe by not paying any attn to which connector got red and which got black? In my mind it can't possibly make a difference to mix the two up, but then again see above discussion of ground vs neutral to see how well my mind works.
    Last edited by Ace Sewer; 07-07-2012, 10:18 PM.
    This is my reminder to myself that no good will ever come from discussing politics or religion with anyone, ever.

  • #2
    Re: 4 vs 3 conductor plugs for kitchen ranges

    the 4 wire system gives the range both 240 and 120 with the white neutral. yes the ground and neutral are typically bonded at the panel, but that's it. i don't believe that you even bond at a sub panel.

    the red and black don't really mean much at the range as they should both pull the same amperage from both sides of the panel. typically the 120 is used for the light, clock and computer panel. but the wattage is next to nothing compared to the 240 circuit. typically you balance the best you can the 2 legs so that the neutral draw is the difference between the 2 legs. so in a perfect world the 50 amp outlet/ 40 -45 amp draw will never exceed the difference between the 2 legs. ad in the case of the range, probably not much more than 100 watts.

    then again electrical is not my #1 trade

    rick.
    phoebe it is

    Comment


    • #3
      Re: 4 vs 3 conductor plugs for kitchen ranges

      Thanks Rick, but that doesn't really answer my questions.

      The additional wire going from 3 to 4 wires is the ground, not the common. I'm aware that the common is there, in both cases, to power 120v components.

      My questions are:
      - is it in any way unsafe to wire a three connector plug into the range designed for the 4 connector plug?
      - if doing that should one jumper the ground to neutral, or leave the ground at the stove unconnected?
      - if that is unsafe, and you should bite the bullet and pull a 4th wire if one isn't there, why? please explain what is the point of a separate ground, as isn't it the same wire as the common since they are tied together at the breaker box anyway?
      - does it matter at all if you flip flop red and black?
      This is my reminder to myself that no good will ever come from discussing politics or religion with anyone, ever.

      Comment


      • #4
        Re: 4 vs 3 conductor plugs for kitchen ranges

        Originally posted by Ace Sewer View Post
        Picked up a craig's list range to replace the ratty one I had. Replacement came with a 4 prong plug. Wall had a 3 prong socket. There was a ground wire in the box not attached to anything, so I went and got the 4 connector socket and wired it in and all seems well.

        My question is why? I felt it would be a little reckless to do but suspect it would have worked just fine to wire the 3 connector cord from the old range into the new one. Can you do this and just jumper the ground to the neutral? what consequences are you risking if you do? is it better to leave the ground unconnected or to jumper it to the neutral? Or is it just crazy unsafe and pull another wire if you only have 3? and if so, why?

        I'm confused in general about the difference between a ground and a neutral since they are (at least in the very few boxes I've had the front off of) connected together at the box anyway. Doesn't this make them the same wire?

        Can anyone explain?

        also, just for my peace of mind, have I done something unsafe by not paying any attn to which connector got red and which got black? In my mind it can't possibly make a difference to mix the two up, but then again see above discussion of ground vs neutral to see how well my mind works.
        Here's the deal. Years ago when electric ranges and colthes dryers came about, they were basically full 240v items some may have had light bulbs or timers that worked on 120v so they used the bonding of the then widely used BX cable as a neutral return fo the 120v itmes. The current was small. It was the only way to get around making them work so the MFG'rs just grounded one side of the 120v devices to the chassis of the unit and the metal jacket of the BX served as a neutral return. I guess it was back in the early 90's when the NEC realized that an awful lot more 120v devices were being added to these ranges and dryers. In some cases the old BX wire had corroded and there were some poor ground connections to the BX jacket. When you pass current on a poor connection you get sparking. The higher the current passing, the bigger the sparks. Since the outer jacket was exposed to outside materials, these sparks could cause a fire or a shock hazard. SO the NEC changed the code and no longer allowed any current whatsoever no matter how small to be passed as "normal operating current" on a ground connection/wire. So, any building construction that came about after that code change would require feed wire that had a seperate insulated neutral wire (white) in addition to a ground to such appliances that required both 240/120v. That would require a 4 prong plug. If you have an older house that had an old range that was wired with 2 wire BX and you are changing to a new unit that has 4 wires looking to be connected, the only way to make it work would be to ground the white wire. Far as I know the code allows this only if there no new construction to the kitchen where new wire could have been added to update to new codes. So what you did was probably Ok as far as code goes only as a grandfather clause. You need to make sure that all your ground connections are tight and that you have a good bond to the BX jackect all along its route back to and including the panel. Romex is better in this regard as the bond is actually a wire and a bteer connection can be made to a wire. Hope this answers your question.

        Comment


        • #5
          Re: 4 vs 3 conductor plugs for kitchen ranges

          Originally posted by Ace Sewer View Post
          - is it in any way unsafe to wire a three connector plug into the range designed for the 4 connector plug?
          Ranges are NOT "designed" for 4-prong plugs. They are designed to accept either. This is why the bond is removable.


          Originally posted by Ace Sewer View Post
          - if doing that should one jumper the ground to neutral, or leave the ground at the stove unconnected?
          DEFINITELY leave the bond in place for a 3-wire installation. That is the whole point.



          Originally posted by Ace Sewer View Post
          - if that is unsafe, and you should bite the bullet and pull a 4th wire if one isn't there, why? please explain what is the point of a separate ground, as isn't it the same wire as the common since they are tied together at the breaker box anyway?
          The fact that they are in a common place in the main panel make absolutely NO difference. It's what they do and their intended purpose once they leave the panel that matters.
          WHat can happen with a 3-wire system is if the NEUTRAL gets compromised you can have objectionable current on the chassis of the range. This will only happen if there is a problem, but it is possible.



          Originally posted by Ace Sewer View Post
          - does it matter at all if you flip flop red and black?
          Not at all.

          Comment


          • #6
            Re: 4 vs 3 conductor plugs for kitchen ranges

            Originally posted by QROKING View Post
            Here's the deal. Years ago when electric ranges and colthes dryers came about, they were basically full 240v items some may have had light bulbs or timers that worked on 120v so they used the bonding of the then widely used BX cable as a neutral return fo the 120v itmes. The current was small. It was the only way to get around making them work so the MFG'rs just grounded one side of the 120v devices to the chassis of the unit and the metal jacket of the BX served as a neutral return. I guess it was back in the early 90's when the NEC realized that an awful lot more 120v devices were being added to these ranges and dryers. In some cases the old BX wire had corroded and there were some poor ground connections to the BX jacket. When you pass current on a poor connection you get sparking. The higher the current passing, the bigger the sparks. Since the outer jacket was exposed to outside materials, these sparks could cause a fire or a shock hazard. SO the NEC changed the code and no longer allowed any current whatsoever no matter how small to be passed as "normal operating current" on a ground connection/wire. So, any building construction that came about after that code change would require feed wire that had a seperate insulated neutral wire (white) in addition to a ground to such appliances that required both 240/120v. That would require a 4 prong plug. If you have an older house that had an old range that was wired with 2 wire BX and you are changing to a new unit that has 4 wires looking to be connected, the only way to make it work would be to ground the white wire. Far as I know the code allows this only if there no new construction to the kitchen where new wire could have been added to update to new codes. So what you did was probably Ok as far as code goes only as a grandfather clause. You need to make sure that all your ground connections are tight and that you have a good bond to the BX jackect all along its route back to and including the panel. Romex is better in this regard as the bond is actually a wire and a bteer connection can be made to a wire. Hope this answers your question.
            Dude, this is SO WRONG it's not even funny!

            The jacket of BX was NEVER, EVER intentionally used as a "return", or neutral, nor did it have ANYTHING to do with the reasoning behind 3-wire range circuits.This was NOT even close to the description of a 3-wire range circuit. If this is what you think I am kind of scared.


            A NEUTRAL was ALWAYS required. ALWAYS. This was allowed to be in the form of SEU cable, where the outer braid is and was a neutral conductor, just like in a main service. This is the ONLY time a neutral is/was allowed to be bare. Other than that an insulated white neutral was required.
            The whole point of a 3-wire system was that the ground was allowed to be bonded to the neutral. The NEUTRAL served both purposes, NOT the other way around.


            I am actually VERY curious as to where you got all this misinformation. That is a pretty long description for almost none of it to be correct.
            Last edited by Speedy Petey; 07-08-2012, 09:11 AM.

            Comment


            • #7
              Re: 4 vs 3 conductor plugs for kitchen ranges

              The OP did not specify what type of wire he had presently feeding his range circuit. If he indeed has a 3 wire BX type cable he can use the 4 prong plug and by code must. I wish he would have specifically called out exactly what he has. Although he asks the question if there is a difference in the black and red wires. Assuming he has a black and red wire, that leads me to beleive he has to have a white wire. If he indeed has a white wire then whatever kind of wire it is must have some sort of a bond in which case there is no excuse for not going by code and using the 4 prong plug which he is compelled to do at this point. SO the correct answer to his question is that if he has the ability to install a 4 prong plug , he must. QUSTION TO YOU PETEY....Have you ever come across a range supplied by a 8/2 or 6/2 BX cable?

              Comment


              • #8
                Re: 4 vs 3 conductor plugs for kitchen ranges

                All well and good, SEU cable cannot be used as such by today's code. The main point I was trying to make is that now under present code, bonds and neutrals have to be seperate after the main disconnect. You could not get by using SEU cable like you did back then. Although the "ONLY" thing that I wrote that might be questionable is that a BX cable would have fit into the same catagory as the SEU cable as far as acting as a neutral. Other than that the rest of my rant was on target. You need not be scared.

                Comment


                • #9
                  Re: 4 vs 3 conductor plugs for kitchen ranges

                  Thanks all for the illumination. I don't know the proper terminology for what I have, so I will just describe it as best I can and hope that will tell you what I have. I have 4 separate insulated solid wires (one eack black, white, red, green) pulled thru flex conduit. Knowing very little about wire gage and unwilling to pull the stove out again to look at the printing on the insulation I am guessing they were 10 or 12 gage. The black, red, and white were wired to the existing 3 prong socket, and if memory serves were a heavier gage than the green. The green was just hanging out in the box not hooked to anything.

                  I bought a socket to match the 4 prong plug on the stove and wired it to the 4 wires in the box. I did put a meter on them first and verified that the black and red were each 120 v to white and to green and were 240 to each other. green and white were a closed circuit.

                  I think what I've done is fine both function and code wise (and please tell me if it is not). I happened to have the ground wire so I bought the 4 prong socket and used it. I was mostly just tapping the reservoir of expertise here to make certain I'd not done something stupid and dangerous, and also just curious about why the separate ground. I now (I think) understand that in normal circumstances there is no need for it, but that it is there to keep the chassis from becoming energized should the neutral fail to work properly.

                  Thanks again.
                  This is my reminder to myself that no good will ever come from discussing politics or religion with anyone, ever.

                  Comment


                  • #10
                    Re: 4 vs 3 conductor plugs for kitchen ranges

                    OK, that helps a great deal. Since you do have a BLACK, RED, WHITE AND GREEN wires, you have all the 4 wires to comply with the present code as to the proper way to hook up the plug. If you have a junction box you would buy a 4 prong outlet which has 4 positions to put wires on. You would hook them up accordingly. Red and black can be switched, but the white and green must be on the correct terminals. The next thing to look at is the range itself. Often times there is a small jumper wire connecting the white wire to the green. Since you have all 4 wires available to you, you would remove the jumper and connect each wire individually to it's respective wire on the terminals behind the range. Essentially what this does is seperate the neutral from the (bond) which is the whole essence of the newer code.

                    Comment


                    • #11
                      Re: 4 vs 3 conductor plugs for kitchen ranges

                      Originally posted by QROKING View Post
                      QUSTION TO YOU PETEY....Have you ever come across a range supplied by a 8/2 or 6/2 BX cable?
                      No, because for a 120/240v (typical) range it would not have EVER been legal or safe. The sheathing of old AC cable carrying current is a VERY dangerous thing.

                      I have certainly seen it with 8/3 or 6/3 BX/AC.

                      You never answered my question, where did you get all that from?

                      Comment


                      • #12
                        Re: 4 vs 3 conductor plugs for kitchen ranges

                        Originally posted by Speedy Petey View Post
                        No, because for a 120/240v (typical) range it would not have EVER been legal or safe. The sheathing of old AC cable carrying current is a VERY dangerous thing.

                        I have certainly seen it with 8/3 or 6/3 BX/AC.

                        You never answered my question, where did you get all that from?
                        Exactly the point I was trying to make PETEY, it would be dangerous "IF" that was the case. I was simply pointing out the dangers such as shock hazard and sparking. JUST because it was not permitted doesn't mean it was never done somewhere, someplace.

                        Comment


                        • #13
                          Re: 4 vs 3 conductor plugs for kitchen ranges

                          Originally posted by QROKING View Post
                          JUST because it was not permitted doesn't mean it was never done somewhere, someplace.
                          OK, no problem.
                          It's just earlier you wrote that this was the common way of doing it. Now you are saying "somewhere, someplace".

                          You wrote:
                          light bulbs or timers that worked on 120v so they used the bonding of the then widely used BX cable as a neutral return fo the 120v itmes. The current was small. It was the only way to get around making them work so the MFG'rs just grounded one side of the 120v devices to the chassis of the unit and the metal jacket of the BX served as a neutral return.
                          So I was foolish enough to think that's what you meant.
                          In all my years I have NEVER seen this done, nor have I heard of it being done, nor have I EVER heard this as the reasoning behind 3-wire range circuits (which I know for a fact is not true).
                          I know I am being trivial, but it is/was distressing hearing this from another electrician.
                          Last edited by Speedy Petey; 07-08-2012, 10:17 PM.

                          Comment


                          • #14
                            Re: 4 vs 3 conductor plugs for kitchen ranges

                            You are right PETEY, I did say that and in that regard it is wrong. I am not old enough to have wired anything like that and surely wouldn't these days of course. That kind of a thing was before my time and probably before the writing of the NEC. We both know full well there are things done that are not right all the time. One time I was in an old underground well pump house. They had a lid that you lifted up and went down a ladder. There was some kind of underground 2 wire non metalic wire feeding the pump. It was 240v. They had a light in the pump house so you could see what you were doing down there. They sank a ground rod to operate the 120vac for the light, it was a little dim but it did work. That's not right, but it was done. I suppose we did clear up this issue however despite the lengthy debate. We do agree on how it is supposed to be done right however.

                            Comment


                            • #15
                              Re: 4 vs 3 conductor plugs for kitchen ranges

                              Originally posted by QROKING View Post
                              One time I was in an old underground well pump house. They had a lid that you lifted up and went down a ladder. There was some kind of underground 2 wire non metalic wire feeding the pump. It was 240v. They had a light in the pump house so you could see what you were doing down there. They sank a ground rod to operate the 120vac for the light, it was a little dim but it did work. That's not right, but it was done. I suppose we did clear up this issue however despite the lengthy debate. We do agree on how it is supposed to be done right however.
                              our well pit light was wired that way for many years, it worked well,
                              Push sticks/blocks Save Fingers
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