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Discussion in 'Electronic Repair' started by Darmok, Jul 19, 2005.

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  1. Darmok

    Darmok Guest


    I finally had my old fuse box replaced with a Cutler-Hammer circuit
    breaker box last year. It has a 'disconnect' in it, to isolate me
    from the local power company. I had this added, as my intention was
    to be able to 'back feed' power to the box via a side door outdoor
    receptacle. Its a standard 12 circuit box, 6 to a side. On the left
    side is a 70 amp dbl breaker which serves as the disconnect. This
    side also has a 20 amp dbl. (220vac) breaker for the central A/C.
    There are 2 open circuits on the left side. On the right side are 6
    20 amp breakers for the rest of the house, various rooms.

    Now, the way I figured it, when the power goes out (like it does about
    every time a squirrel farts around here), all I'd have to do is
    disconnect from the power company, flip the A/C breaker (for safety,
    and turn it off at the thermostat), and then plug my generator into
    the outdoor receptacle via a dbl. male extension (using very high
    quality 12-3 Polar/Solar GE cable ... about 3/4" diameter).

    Well, I had a chance to try this out a couple days ago, when power was
    out for 4 hours (we had a thunderstorm ... not a bad one ... we just
    lose power a LOT). I plugged in the generator after it leveled out,
    and was greeted with lights when I entered the house. HOWEVER, there
    were 3 rooms where there was no power. 3 rooms had power. When I
    went to the circuit box, I pulled the cover and, using my DMM, I found
    that every other circuit breaker had no AC on it: #1 hot; #2 dead; #3
    hot; #4 dead; #5 hot; #6 dead. I sort of figured that the entire
    right side of the box would be powered up, but maybe there's some kind
    of alternating pattern to "balance the load". That's the only thing I
    can think of. Can anyone shed light on why I have power to only half
    the circuits? I'm a professional electronic technical specialist, and
    work with SMT/BGA boards every day ... but I'm NOT an electrician, so
    I'm out of my area of expertise.

    TV's and computer, radios and lights all worked fine. A ceiling fan
    in the living room was making a weird noise, and it finally stopped
    circulating after a bit. I thought it died, for some strange reason,
    however, when the power came back on, and I once again connected to
    the power company, the ceiling fan worked fine. Don't understand that
    one at all. Do all motored items not work with generator power? Am I
    wrong to think that my refrigerator will work properly with generator
    power? (the kitchen was one of the rooms that didn't power up)

    With the disconnect turned off, and the A/C breaker OFF, would it be
    safe to jumper something to get power to the unpowered circuits?

    Thanks for any help.
  2. NSM

    NSM Guest

    Because some devices have 220 fed to them so you need to have both breakers
    adjacent. That's normal. Either get a split 220 generator properly installed
    or just unplug things and run them from the generator via extension cords.
    Hard to say why. Maybe it has a solid state control? Remote?
    If the generator delivers good 60 cycle power it should work fine.
    Everything you suggest is nasty and could kill someone. Get a proper
    isolater switch from Home Depot etc. If you back feed power up the lines by
    forgetting something, you could kill a lineman or someone else one day.

  3. <snippety-two>

    NononononoNO! NEVER run emergency power that way!

    For starters, circuit breakers don't work reliably in reverse.
    That's why they have a 'Line' and 'Load' side. If you get an overload
    while running your generator into an outlet, the breaker may not trip.
    This could easily start a fire, damage your generator, and cause your
    home insurance carrier not to honor claims related to any damage from
    such activity.

    The other issue, and the reason you were missing power to some
    rooms, is that modern residential power lines are split-phase. You get
    two 'hots' which, between them, carry 220V, and a neutral line. The two
    hot leads are usually split inside the breaker box to avoid loading one
    side too heavily. Your generator was likely only providing power to one
    of the hots.

    Another factor of Why You Don't Want To Do It This Way: It's in
    direct violation of the National Electrical Code, and probably local
    codes as well. If you get caught running things that way, you could have
    many more worries than just the risk of overload and a few dead rooms.

    The ONLY way to correctly run emergency power, so that there is
    minimal risk to you and any power company folk who happen to be working
    on the lines, is to install a proper generator transfer switch. Such are
    readily available from home-improvement stores (I prefer Lowe's,
    personally) or industrial electric suppliers such as Platt Electric or

    They're not particularly difficult to install, but not all states
    or counties allow the homeowner to do electrical work, and you will have
    to have the completed installation inspected no matter what (if you
    expect your homeowner's insurance company to continue to honor your

    The thing to do is check with your local government's electrical
    or home inspection office. They will tell you if (a), you as the
    homeowner are allowed to do electrical work, and (b), what permit(s)
    you'll need to get a transfer switch going.

    You may be better off leaving the job to a professional

    And no, BTW. It would not be at all safe, for you or any power-
    line workers, to "jumper" anything in the box. Get a transfer switch.

    Happy tweaking.

    Dr. Anton T. Squeegee, Director, Dutch Surrealist Plumbing Institute.
    (Known to some as Bruce Lane, ARS KC7GR,
    kyrrin (a/t) bluefeathertech[d=o=t]calm --
    "If Salvador Dali had owned a computer, would it have been equipped
    with surreal ports?"
  4. Jamie

    Jamie Guest

    you need a generator with 2 phase out .
    that is 2 120 volt outs that are out of phase with
    a common/neutral.
    commercial power in the US for residents normally have a center tapped
    transformer that will give you 120 from outer tap to center and if you
    need 220 for dryer, the 2 outer only are used ! because they are out
    of phase from each other bye 180 degrees, you can get double your
    in houses, its common to split up the load and try to equally load
    the 2 120 lines coming in.
    this means you should have a generate that outputs 2 120 lines that
    are out of phase.
  5. James Sweet

    James Sweet Guest

    Get a generator transfer switch, it's the only safe and legal way to do it
    and you'll save yourself a lot of headaches. You can get them at any
    hardware store, they have a number of switches that let you select
    individual circuits between line and generator.
  6. James Sweet

    James Sweet Guest

    Circuit breakers will work just fine in reverse, the current is AC so it's
    reversing rapidly anyway but either way it makes no difference at all.
    There's plenty of other reasons not to do what he's contemplating though.
  7. Stan

    Stan Guest

    }For starters, circuit breakers don't work reliably in reverse.

    Explain please...what's inside a curcuit breaker that needs to
    have the AC connected to the LINE to not malfunction?

  8. Ross Herbert

    Ross Herbert Guest

    Firstly, I would have thought it would be mandatory for the main
    utility supply to have a supply disconnect switch at the entry point
    to the main distribution box, and it would not be something you could
    elect to add at your own discretion.

    Also, you didn't say whether the disconnect switch allows selection of
    either the mains or generator supply or whether this is performed
    safely by following a defined manual sequence for change-over.

    The main supply disconnect switch usually consists of make contacts
    only and this switch is either on or off. Assuming that only active
    and neutral are passing through the switch then it will consist of 2
    make contacts.

    In order to create a demarcation point for the house wiring and the
    new generator input socket you should follow the mains disconnect
    switch with a similarly rated switch which has double change-over
    contacts (break before make). One side of the contacts will connect to
    the active and neutral outputs from the main utility disconnect
    switch, while the other side will connect to the respective line and
    neutral pins on your generator input socket. The common side of the
    switch will connect to the house distribution circuit breakers and
    neutral link. The switch allows you to select either the main utility
    supply or the auxiliary generator supply without the possibility of
    accidentally connecting both the supplies together. It provides a
    fail-safe system to prevent such an occurrence, and may be mandatory.

    You may be able to get away with substituting the make only main
    supply disconnect switch with the change-over switch, but then there
    will be no clear demarcation point between the main utility supply
    side of the wiring and the auxiliary generator supply side.

    Ross Herbert
  9. Darmok

    Darmok Guest

    - big snip -

    Thanks to all who've replied so far ... given me quite a bit to
    think about.

    FWIW, my circuit box was installed by a certified electrician .. I
    simply didn't feel competent to do something on that scale. They
    pulled my meter on the side of the house in order to install it.

    The 4KW generator I have (by Coleman) has 2 AC outlets, which, when
    measured unloaded, provide 130 VAC. I haven't tried to measure across
    the 2 outlets to see if 260 VAC is available, but I suspect that I
    will find that is true.

    I suppose I could wire up some kind of cross-over switch by the box on
    the side of the house next to my Central A/C compressor unit. That
    would be the logical place to bring in 220/240/260 vac.

    I will continue to read your comments, and check at Home Depot or
    Lowe's for the switch many of you have described.

  10. NSM

    NSM Guest

    I would never wire one backwards, however they should work either way. They
    are more subtle than most people know however.

  11. Jim Adney

    Jim Adney Guest

    Perhaps you didn't tell him all of what you had in mind. A good
    electrician would have explained the danger, and illegality, of
    installing your backup power this way.
    My guess, and it's just a guess, is that you'll find that both outlets
    put out the same 130V. There should be a spec plate somewhere on your
    generator that gives its output voltage. If it doesn't mention
    something above 200 V somewhere, then you have a very straightforward
    120V single phase generator.
    This transfer switch, what you're calling a cross-over switch, needs
    to be inserted in the line between your meter and your breaker box.
    It's purpose is to make sure that there is no way that you can ever
    connect both the generator and the line to the house, or the generator
    to the line. It's for your safety, the safety of anyone working on a
    downed line in your service area, and the safety of your generator. It
    could also be wired up permanently with a cord which you could safely
    plug into your generator when the need arises. You don't EVER want to
    have a male plug that can be hot when unplugged.

  12. James Sweet

    James Sweet Guest

    The transfer switch doesn't go between the meter and the panel, it wires
    into the panel and the individual circuits go between the breaker output and
    the hot wire to the circuit you wish to have backup power available to.
    They're metal boxes with a plug for the generator and a flex whip to wire
    into the panel, they start at around $120 for a small one.
  13. Jim Adney

    Jim Adney Guest

    Then let me rephrase:

    The transfer switch goes into the line feeding whatever load you wish
    to provide emergency power to. In his case, he's asking to feed the
    whole box, which means that he needs one of the larger transfer
    switches and he needs to put it in the line between his meter and his
    service panel.

    Of course he probably also needs a bigger generator, and one rated at
    220V, but the box he is asking to power really isn't all that big, so
    I suspect that he just needs a 220V generator and a transfer switch
    rated to handle the total box power.

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