Can I ground a 10/3 ungrounded wire?

Discussion in 'Electrical Forum discussion & Blog' started by enviroko, Aug 28, 2007.

  1. enviroko

    enviroko New Member

    Messages:
    37
    I would really like to use this wire for now until I can get it replaced but I don't want it left ungrounded. I want to temporarily use it for an electric dryer. It is already connected to my old fuse box and runs over close to the dryer.
  2. Bob NH

    Bob NH In the Trades

    Messages:
    3,317
    Location:
    New Hampshire
    NEC 250.140 Frames of Ranges and Clothes Dryers.

    The Exception to 250.140 permits an existing branch circuit without a grounding conductor to be used for a Range or Clothes Dryer if all of the following conditions are met. (edited for your described condition)
    (1) A 120/240 Volt single phase circuit
    (2) Grounded conductor (neutral) at least #10
    (3) Neutral is insulated; or if it is not insulated then it is part of a Type SE Cable and the branch circuit originates at the service equipment (not a sub-panel).
    (4) Grounding contacts of receptacles furnished as part of the equipment (such as an outlet on the control panel of a range) are bonded to the equipment.

    If the dryer has a 3-wire cord, then you can use a 3-wire receptacle.

    If you are connecting a dryer that already has a 4-wire cord, then the frame of the dryer must be connected in a way that the frame is grounded. That could be done by connecting the ground in the 4-wire receptacle to the neutral terminal in the connector. If you do that, then you should put a note on the receptacle to tell future users that the grounding terminal is connected to the neutral terminal. If the connection is made internal to the dryer then you should put a note on the dryer that the frame is connected to the neutral.

    You should be aware that both of these conditions result in grounding the frame of the dryer, because the neutral, also called the "grounded conductor", is in fact grounded. The conductor that is absent from your circuit is called the "equipment grounding conductor" and has been used in only recently (I don't know how recently) installed dryer and range circuits.
  3. snafflekid

    snafflekid Electrical Engineer

    Messages:
    45
    I'm trying to think of a case where this would not be true.
  4. enviroko

    enviroko New Member

    Messages:
    37
    Ok Bob, thanks for the information. I would like to clarify to make sure that I'm understanding you right. Are you saying to connect the ground wire from the dryer's receptacle to the neutral wire of the old 10/3 wire? Here are some pics to make sure that I am conveying the info to you correctly.

    Dryer plug and receptacle already in place.
    [​IMG]

    Disconnected wire coming from receptacle.
    [​IMG]

    Line to fuse box.
    [​IMG]

    [​IMG]
  5. Bob NH

    Bob NH In the Trades

    Messages:
    3,317
    Location:
    New Hampshire
    It is a little confusing to me because you have two different wires.

    The usual situation would be for something like the "line to the fuse box" to be connected to the three terminals of the receptacle.

    You don't indicate where the "disconnected wire coming from receptacle" is going to or coming from. That is an extra wire that I didn't infer existed based on your first posting. Is that piece of 4-wire going to be part of your new circuit?

    The usual way to hook this up would be for the "line to fuse box" to be hooked to the 3 terminals of the receptacle with the twisted ground/neutral wire going to the L shaped terminal.

    If you need the 4-wire for an extension to make up the length from where you want the outlet to the point where the "line to fuse box" wire ends, then you should connect the 4-wire to the 3-wire in a junction box using wire nuts, put the receptacle where you need it to plug in the dryer, and connect the receptacle to the 3-wire in the junction box. You can use the white wire + black + red to extend the circuit.

    http://www.selfhelpandmore.com/switchoutlet/dryer/dryershowall.htm

    http://fixitnow.com/appliantology/dryercords.htm
  6. enviroko

    enviroko New Member

    Messages:
    37
    Sorry bout that. I'll try to clarify and thanks for being patient.

    The wire coming from the receptacle is from a previous dryer hookup (before I owned the house) and it is already up in the floor joists near the junction box that I want to use. The old line connected to the fuse box is also up in the floor joists and is currently in the junction box. Sort of like this...

    [​IMG]





    Here are the pics again from the dryer to the line going to the fuse box. If I connect the wires according to my arrows, is that correct? What do I need to do with the ground wire?

    [​IMG]

    Thanks Bob!
  7. Bob NH

    Bob NH In the Trades

    Messages:
    3,317
    Location:
    New Hampshire
    The ground wire in the 4-wire cable is superfluous as long as the 3-wire back to the panel and the 3-wire cord are used. Fold it out of the way so it doesn't short to anything. You will want it if you ever replace the 3-wire SE cable and the 3-wire cord.

    The other connections look fine. That black wire of the 4-wire cable appears to have split insulation, but it might be just a photo-artifact. If the wire is exposed it must be fixed.
  8. enviroko

    enviroko New Member

    Messages:
    37
    Thanks Bob! You have been a big help. There's lots of room to cut and restrip both wires.
  9. enviroko

    enviroko New Member

    Messages:
    37
    Oh, another question. Shouldn't I connect the ground wire to a cold water pipe just to be safe? I thought about using a wire nut to extend it over and clamp it to the pipe. It's only about two feet away.
  10. Furd

    Furd Engineer

    Messages:
    446
    Location:
    Wet side of Washington State
    Nope. If you cannot run the equipment grounding conductor all the way back to the panel the power conductors run from then don't connect it to anything.
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