220 volt 3-wire vs. 4-wire

Discussion in 'Home Repair' started by M.Burns, May 11, 2008.

  1. M.Burns

    M.Burns Guest

    I have a 220-volt electric dryer with 3-prong plug going into a 3-prong
    receptaclet (2 blades on a 'V', and third L-shaped prong).
    Do newer electric dryers have a 4-wire plug with a ground?
    Would I have to replace the 20-year-old 3-prong receptacle?
    Just technically speaking, could the ground prong on the male plug be cut
    off to fit the old outlet (similar to what people of done for years on
    110-volt stuff). Or is the wiring for 4-wire 220 volt completely different
    because of 2 hot wires, neutral, ground, etc.?
    M.Burns, May 11, 2008
    #1
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  2. M.Burns

    RBM Guest

    "M.Burns" <> wrote in message
    news:a%CVj.84$...
    >I have a 220-volt electric dryer with 3-prong plug going into a 3-prong
    >receptaclet (2 blades on a 'V', and third L-shaped prong).
    > Do newer electric dryers have a 4-wire plug with a ground?
    > Would I have to replace the 20-year-old 3-prong receptacle?
    > Just technically speaking, could the ground prong on the male plug be cut
    > off to fit the old outlet (similar to what people of done for years on
    > 110-volt stuff). Or is the wiring for 4-wire 220 volt completely
    > different because of 2 hot wires, neutral, ground, etc.?


    The NEC allows you to use an existing three wire electric dryer feed and
    receptacle. Typically, dryers don't come with cord sets, so you specify the
    one you need for your outlet. Any new installations require a four wire
    feeder and receptacle. If, you do have a four wire feeder, it would be
    sensible to install a four wire outlet on it, then get the appropriate cord
    set with the new dryer
    >
    >
    RBM, May 11, 2008
    #2
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  3. M.Burns

    EXT Guest

    Canadians reading this should note differences that in Canada, dryers and
    non-built in stoves have all come with 4 prong cords for the past 35 years.
    Code requires receptacles that are fed by what is labeled a "3 wire plus
    ground" cable. It is not Code compliant to connect the neutral and ground
    together in the appliance.

    "S. Barker" <> wrote in message
    news:D...
    > Dryers don't come with cords. Just use your old cord on the new dryer and
    > go. You'll have to be sure the grounding jumper is in place on the new
    > dryer like it is on your old one.
    >
    > s
    >
    >
    > "M.Burns" <> wrote in message
    > news:a%CVj.84$...
    >>I have a 220-volt electric dryer with 3-prong plug going into a 3-prong
    >>receptaclet (2 blades on a 'V', and third L-shaped prong).
    >> Do newer electric dryers have a 4-wire plug with a ground?
    >> Would I have to replace the 20-year-old 3-prong receptacle?
    >> Just technically speaking, could the ground prong on the male plug be cut
    >> off to fit the old outlet (similar to what people of done for years on
    >> 110-volt stuff). Or is the wiring for 4-wire 220 volt completely
    >> different because of 2 hot wires, neutral, ground, etc.?
    >>

    >
    >
    EXT, May 11, 2008
    #3
  4. M.Burns

    Guest

    Re: 220 volt 3-wire vs. 4-wire

    On May 11, 12:08�pm, "EXT" <> wrote:
    > Canadians reading this should note differences that in Canada, dryers and
    > non-built in stoves have all come with 4 prong cords for the past 35 years..
    > Code requires receptacles that are fed by what is labeled a "3 wire plus
    > ground" cable. It is not Code compliant to connect the neutral and ground
    > together in the appliance.
    >
    > "S. Barker" <> wrote in message
    >
    > news:D...
    >
    >
    >
    > > Dryers don't come with cords. �Just use your old cord on the newdryer and
    > > go. �You'll have to be sure the grounding jumper is in place on the new
    > > dryer like it is on your old one.

    >
    > > s

    >
    > > "M.Burns" <> wrote in message
    > >news:a%CVj.84$...
    > >>I have a 220-volt electric dryer with 3-prong plug going into a 3-prong
    > >>receptaclet (2 blades on a 'V', and third L-shaped prong).
    > >> Do newer electric dryers have a 4-wire plug with a ground?
    > >> Would I have to replace the 20-year-old 3-prong receptacle?
    > >> Just technically speaking, could the ground prong on the male plug be cut
    > >> off to fit the old outlet (similar to what people of done for years on
    > >> 110-volt stuff). Or is the wiring for 4-wire 220 volt �completely
    > >> different because of 2 hot wires, neutral, ground, etc.?- Hide quoted text -

    >
    > - Show quoted text -


    I will add that i think 3 wire is a bad idea, with a bad day it could
    be a real hazard....

    buy a new dryer? then get a new cord and updated outlet
    , May 11, 2008
    #4
  5. M.Burns

    Beachcomber Guest

    Re: 220 volt 3-wire vs. 4-wire


    >> - Show quoted text -

    >
    >I will add that i think 3 wire is a bad idea, with a bad day it could
    >be a real hazard....
    >
    >buy a new dryer? then get a new cord and updated outlet


    Problem is - Many older houses are not wired for the updated outlet.
    If you don't have the proper wiring at the outlet (2 hots - Neutral
    -Ground), you are not allowed to install the 4 wire code-compliant
    outlet (vs. the old 3 wire outlet). Hence the grandfather clause...

    For many older houses - installing new dryer wiring would be difficult
    (expensive) and involve pulling new wires and possibly ripping up
    walls.

    The NEC allowed the 3 wire exception to save on copper during WWII.
    Then, one or two people got electrocuted by their dryers and they
    decided to go back to 4 wire some years ago.

    Apparently Canada never did this. Anyone know for sure?
    Beachcomber, May 11, 2008
    #5
  6. M.Burns

    Guest

    Re: 220 volt 3-wire vs. 4-wire

    On May 11, 2:05�pm, (Beachcomber) wrote:
    > >> - Show quoted text -

    >
    > >I will add that i think 3 wire is a bad idea, with a bad day it could
    > >be a real hazard....

    >
    > >buy a new dryer? then get a new cord and updated outlet

    >
    > Problem is - �Many older houses are not wired for the updated outlet.
    > If you don't have the proper wiring at the outlet (2 hots - Neutral
    > -Ground), you are not allowed to install the 4 wire code-compliant
    > outlet (vs. the old 3 wire outlet). �Hence the grandfather clause....
    >
    > For many older houses - installing new dryer wiring would be difficult
    > (expensive) and involve pulling new wires and possibly ripping up
    > walls.
    >
    > The NEC allowed the 3 wire exception to save on copper during WWII.
    > Then, one or two people got electrocuted by their dryers and they
    > decided to go back to 4 wire some years ago.
    >
    > � Apparently Canada never did this. �Anyone know for sure?


    for safety its likely worth the effort.

    just look at all the other updates required today, GFCI, arc fault,
    getting rid of K&T to obtain insurance, replacing fuse boxes, etc etc.

    wonder why the dryer exception has survived?
    , May 11, 2008
    #6
  7. M.Burns

    KLS Guest

    Re: 220 volt 3-wire vs. 4-wire

    On Sun, 11 May 2008 17:48:32 -0400, wrote:

    >On Sun, 11 May 2008 14:38:50 -0700 (PDT), ""
    ><> wrote:
    >
    >>wonder why the dryer exception has survived?

    >
    >Not much of a body count to justify changing it.


    Beautifully put. :D
    KLS, May 11, 2008
    #7
  8. M.Burns

    Beachcomber Guest

    Re: 220 volt 3-wire vs. 4-wire

    On Sun, 11 May 2008 18:16:08 -0500, "S. Barker"
    <> wrote:

    >if the grounding jumper is properly in place, then it's just as safe as a 4
    >wire. IF in fact anyone was actually shocked by a dryer, then it was a
    >dufus installation problem, not a # of wires problem.
    >


    Safe is a relative term. The safest installation would be to have
    the neutral separate from the grounded frame of the dryer, especially
    since in the US, dryers have 120 V. motors and thus there is always
    neutral current flowing when the appliance is operating.

    The exception was apparently allowed because it is extremely rare for
    the neutral to become disconnected, which could potentially energize
    the frame of the dryer to 120 V. Most dryers are installed next to a
    washing maching, which is more-than-likely to be properly grounded.
    Thus you would have a possible shock hazard.

    But, as mentioned before, most owners of older homes are not going to
    want to spend the money to rewire the dryer circuit for something that
    has basically worked fine for 10-40 years, if the 3-wire dryer plug
    option is allowed.
    Beachcomber, May 12, 2008
    #8
  9. M.Burns

    Mark Guest

    Re: 220 volt 3-wire vs. 4-wire


    > if the grounding jumper is properly in place, then it's just as safe as a 4
    > wire.



    This is NOT true.

    The three wire system, even when properly installed to code is
    dangerous becasue an OPEN circuit (which can happen) in the 3rd ground/
    neutral wire) can end up energizing the metal chassis of the dryer
    through the 120 volt clock motor or other 120 volt parts in the
    dryer. If someone then touches say the properly grounded washing
    machine and the dryer at the same time, they could get a dangerous
    shock.

    That being said, I have a three wire install in my house and it can be
    made safe with the simple addition of an axtra ground wire connected
    from the case of the dreyer to a good ground such as a nearby water
    pipe. I have a ground wire connected between the dreyer and the
    washer, therefore there can be no voltage across them.

    Yes three wire system were code and can be grandfathered to code, but
    they can still be dangerous and I would add the extra ground wire to
    be safe. Rewiring for a full 4 prong plug can be expensive if a new
    cable has to be pulled. Adding an external ground wire is cheap and
    easy and effective.

    Mark
    Mark, May 12, 2008
    #9
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