Oven neutral or not

Discussion in 'Electrical Forum discussion & Blog' started by Sleepless, Jul 3, 2014.

  1. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
    2,540
    Location:
    North Carolina
    Yes a four wire cable would be required
    A four wire is safer than a three wire only if the bond if removed in the range itself
    The ground is required to be in the same cable as the rest of the conductors or no ground can be used from another circuit.
    Terry likes this.
  2. Reach4

    Reach4 Well-Known Member

    Messages:
    2,423
    Location:
    IL
    What do you say about this code exception and the cable that was run in the 70s?
    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 connected to the equipment grounding conductor 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 connected to the grounded circuit conductor if all the following conditions are met.​

    https://www.inkling.com/read/nation...sociation/chapter-2/vii--methods-of-equipment
  3. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,143
    Location:
    New England
    In a properly working device, all current that goes out one power lead MUST go back through the other power lead. To get 120vac from a 240vac circuit, the return lead is the neutral...for 240vac, the return lead is the other 240vac lead (return is somewhat ambiguous, since power is actually flowing back and forth).

    A GFCI circuit looks for the 'loss' of some of that return current (IOW, it somehow made it to ground instead of the current carrying conductor - the neutral or the other 240vac hot lead). That 'loss' of current could easily be going through you to ground. That imbalance means current is going somewhere it is not designed to go. Back at the main panel, ground and neutral are tied together, but depending on the length of the wires and the amount of current that they are carrying, at the other end, they may or may not have exactly the same potential (which is the reason why the code was changed to separate them). The ground is a safety return wire that should provide a path to trip the circuit breaker if there's a short and neutral is compromised in some way. If you're moving the device, it is my understanding that the circuit must be brought up to current codes, and that would mean running a new cable. The code does not allow you to use a ground from another cable to augment the ground at the newly installed device.

    So, a GFCI does not require a ground attached at all to work...it is looking for there to be the same power in both power leads, and if it isn't, there's a problem and it trips, removing power to protect you.
  4. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
    2,540
    Location:
    North Carolina
    In the original post the circuit is being moved therefore it is no longer existing but being installed.
    There are such things as timers and lights that require the installation of a neutral. An equipment grounding conductor is required with all ungrounded conductor installs. In a three wire circuit for a range or dryer the bare conductor is being used as a neutral not an equipment ground.
    In any circuit including multiwire circuits, meaning a neutral is present, contact with any two current carrying conductors results in a short circuit which opens the fuse or circuit breaker really fast.
    One end of the equipment grounding conductor is connected to the neutral in the service equipment and the other end is connected to all exposed metal surfaces which includes the metal of ranges and dryers. Should either of the ungrounded conductors come into contact with the metal it would be the same as coming in contact with the neutral and the overcurrent devices opens quickly.
    Should the neutral come into contact with the metal and an equipment grounding conductor is properly installed it parallels the return path for the current This lowers the resistance of the return path which will have a drastic effect when someone comes into contact with the metal.
    In a three wire circuit the person touching the dryer becomes the first parallel path which greatly increases the current potential for that person.
    If a four conductor is used without removing the bond in the range or dryer there is the parallel path between the neutral and equipment ground which is a violation of the code.
    Terry likes this.
  5. PatrickH

    PatrickH New Member

    Messages:
    17
    Location:
    Virginia
    Sleepless,

    Installing new branch circuit for your new range can't be any more painful than considering all these options... How about a new gas range instead? ;)
  6. Sleepless

    Sleepless New Member

    Messages:
    10
    Actually a gas wall oven would be my preference, but they are very rare (I suspect there are concerns about gas venting). (The cook top will be induction and is in a separate location from the oven.)

    Looks like we're going to rip up some perfectly good sheetr0ck.

    I still think that the easiest solution is an oven the runs on 240 rather than 120/240. I have looked and have yet to find one.
  7. Sleepless

    Sleepless New Member

    Messages:
    10
    Several years ago I installed a transformer at our wellhead with a 240 VAC primary 120/240 VAC secondary. This allowed for a GFCI protected circuit for a light and heat tape. (You should have seen the electrical mess that the well installer left!)

    Certainly something like this could be installed (by the manufacturer) of a wall oven. It would add to the cost, but would be cheaper than running a new 4 wire circuit.
  8. PatrickH

    PatrickH New Member

    Messages:
    17
    Location:
    Virginia
    You mentioned you were going to take out the sheetrock in the kitchen. Based on what you've said, I'd guess that there's a floor above? If so, then are there any second floor closets or interior walls above your kitchen that you could fish a new circuit to the attic through?
  9. Sleepless

    Sleepless New Member

    Messages:
    10
    That would probably be possible, but a rather long run. I suspect that I will hire an electrician to do their thing with long drill bits and fishing rods.
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