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Why does my main breaker box have a shared ground/neutral?

Discussion in 'Electrical Engineering' started by KR Williams, May 10, 2004.

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  1. KR Williams

    KR Williams Guest

    Because the current is supposed to flow in the neutral, and the
    ground is there as a *safety*. I.E. *ALWAYS* at ground, no
    matter how the current flows. Think of an open neutral somewhere
    in your house. If the ground, which is hooked to appliance
    cases, were the same as the neutral, these case would suddenly be
    at 120V. ...not good.

    Ground is your friend (usually). Neutral is there as a return
    for electrons. They're tied together at your entrance panel to
    keep the peace. ;-)
     
  2. Brian

    Brian Guest

    A neutral is only a return in direct current applications.


    Because the current is supposed to flow in the neutral, and the
    ground is there as a *safety*. I.E. *ALWAYS* at ground, no
    matter how the current flows. Think of an open neutral somewhere
    in your house. If the ground, which is hooked to appliance
    cases, were the same as the neutral, these case would suddenly be
    at 120V. ...not good.

    Ground is your friend (usually). Neutral is there as a return
    for electrons. They're tied together at your entrance panel to
    keep the peace. ;-)
     
  3. Your picture shows main lugs only. Where is the main service disconnect
    and overcurrent protection?
    The grounding conductor, grounded conductor, and grounding electrode
    conductor are suppose to be bonded at the service disconnect. Your panel
    does not look like a service to me.
    I have an article on this at:
    http://www.electrician.com/electa1/ground100.html
     
  4. daestrom

    daestrom Guest

    Use a screwdriver whose shaft is insulated for this purpose. In a pinch,
    spiral wrap the shaft with electrical tape, with 1/2 overlap so each point
    has two layers of tape. Just leave the last 1/4 to 1/2 inch of the tip
    exposed.

    Some boxes, with a lot of stray bare conductors not neatly tucked in can be
    very scary places. Especially when you try to push them aside to reach a
    breaker :)

    daestrom
     
  5. That's all there is except for the meter.

     
  6. It is very unusual to have ready access to the mains when they are only
    protected by the primary fuse at the service transformer. That seems to be
    you situation.
    Before working on this panel hot I would carefully perform a hazard analysis
    to determine the risks that you may be taking. The fault current could be
    extremely high and you could be placing yourself in harms way by working
    this panel hot. I am an electrician with over 40 years experience and I shy
    away from working on any hot circuits on the supply side of a service
    disconnect. These hot circuits are like working with nitroglycerine.
    I would contact the utility company and see if they can pull the meter to
    de-energize the panel before working on it. I would also ask for a courtesy
    inspection by any authority having jurisdiction including the utility
    company. Most utility companies seal any disconnect, box, meter, or panel
    that allows direct access to the supply side energized circuits.
     
  7. Yup, that's how this one is, there's two mains, one on each side. Then
    there's about 2 pole breakers above the mains that can't be turned off.
    Unfortunately I have to add one there so I'll have to do it hot.
     
  8. Doh, I meant to say there's one main on each side (60 amps) and there
    are also about 6 slots above those (2 poles).
     
  9. Ok, I just looked and I guess I thought there were more. There are 5
    breakers, one emtpy slot.
     
  10. Blue Crown

    Blue Crown Guest

    Gerald, don't you remember when it was legal to run unfused service
    entrance conductors for long distances without a main overcurrent
    protection? You still could not have more than 6 main disconnects at
    the panelboard. Most of those panelboards were "split-buss" panels,
    where one of the mains was used to feed the lighting and receptacles.
    Now, of course, you cannot run the service entrance more than about 5
    feet or less without a main breaker. Usually just on the opposite wall
    back-to-back with the meter box. Make sense? Later... Blue Crown
     
  11. Cougercat

    Cougercat Guest

    The neutral and ground are usually tied together in the CB panel or fuse
    panel of a residence. A #4 copper wire should go from the neutral bar to a
    8 foot ground stake that has been pounded into the ground someplace.

    Your best bet would be to install a 30 amp single trip/dual circuit breaker
    (or 2 circuit breakers with a common trip) and feed your welder off of it.

    --jj
     
  12. That's for the water heater. I guess I could wait until a thunderstorm
    brings a tree down in my neighborhood. It happens often this time of
    year. It was off for 3 days last winter.. I just really don't want to
    work on it hot. I'm not worried about exceeding 100amps, even though the
    oven is 40, air conditioner 60, main lighting 60x2, dryer 30, water
    heater 40, etc. We rarely run all of these at the same time. I'm
    probably only rarely going to use the 50 amp for the welder/air compressor.
     
  13. Bah, I just looked at it more closely, and it's going to take a long
    time to hook everything up. I might have to move some other breakers. I
    guess I'll have to have the meter pulled.
     
  14. Bob Weiss

    Bob Weiss Guest

    Unless you can prove 25 ohms or less ground resistance with only one
    rod. As a practical matter, you end up driving the second rod...:)

    Bob Weiss N2IXK
     
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