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Discussion in 'Electrical Engineering' started by Rob, Sep 17, 2003.

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  1. Rob

    Rob Guest


    storm comming!!!! this friday.

    i have a honda 11hp 6850 max 5500 norm gen.

    what do you think of this set up

    -put in a 220v 30 amp breaker in home panel & wire it to another 30 amp
    disconnect thats tied to a female recepticle for the generator plug.
    --if power fails pull the main & turn off all breakers
    --close the 30amp breaker on the main panel & close the disconnect.
    --fire up the generator & plug it in.slowly turning on only essential
    breakers.(conservatively not to exceed gen. rating)
    **** how does this affect the load on the left & right poles of the
    generator if theyre not balanced?
    In otherwords I have 2 lives 1 neutral & a ground tied & isolated to my gen.
    if the left side of my panel (120v) draws more than the right will that
    affect the gen.? or as in theory it all comes back to source and
    balances.....I think.

    Feedback appreciated
    but not backfeed(haha)

  2. Rob

    Rob Guest

    hey guys....
    a disconnect is a manual trow over switch....sorry for the confusion.
  3. I agree with BG, do it right. It will keep you from killing yourself or the
    poor lineman working in your area. Get a manual transfer switch from an
    electrical supply store.

    Charles Perry P.E.
  4. Guest

    You miss the point. 1) Your disconnect will energize your circuit
    breaker panel without disconnecting the panel from the utility
    lines. 2) The cord you intend to use will have male plugs at each
    end. (Thus the name "suicide cord")

    Both of the above are unsafe.
  5. Rob

    Rob Guest

    your missing
    main breaker the 1st post

  6. As a slight aside, I find it really interesting that you can even *suggest*
    such a wiring scheme over there - let alone actually do it.

    In Oz/NZ, any modifications to a domestic switchboard to fit a generator
    connection *must* be done by a licensed electrician *and* inspected by the
    local power authority.. and then your insurance company will disown you
    before you can turn the power back on to your house! I guess that's to
    prevent Joe Householder killing himself...

  7. Rob, you said, "if power fails pull the main & turn off all breakers".

    The changeover from normal supply to generator supply must be mechanically
    interlocked such that it is not *physically* possible to connect the
    generator to the utility - even by accident.

  8. Guest

    No, I am not missing main breaker off -
    I read the first post. Now, re-read what I posted:
    "1) Your disconnect will energize your circuit
    breaker panel without disconnecting the panel from the utility

    Your disconnect is not mechanically connected to your main
    breaker. Therefore, your disconnect CANNOT trip or pull the
    main breaker. In your first post you said:
    "--if power fails pull the main & turn off all breakers"
    You are indicating that YOU (or some person)
    will pull the main. The DISCONNECT will not do it.

    You came here asking what people thought of your idea:
    "what do you think of this set up"
    People are trying to tell you what they think, but you are
    missing it.

    What you need is a TRANSFER SWITCH, not a DISCONNECT.
    The setup, as you described it, is unsafe for the reasons
    already posted. A transfer switch guarantees that the utility
    lines cannot become energized by the generator. Forget to pull
    the main in your method, and those lines can become energized.
  9. Guest

    People actually do far worse that what has only been suggested
    here, in spite of our rules to the contrary. I imagine its the
    same in Oz/NZ - but your rules may have "more teeth". I imagine
    someone here may have gone to jail for violating the electrical
    code, but I've never heard of it. People have died due to shoddy
    and illegal wiring.
  10. If you forget to turn main breaker off, or if someone else turns it back
    on, you will energize the lines leading to the distribution pole and
    there will be 7200 Volts waiting for an unsuspecting linesman. bad idea.
    Better to pull the meter and hardwire into the meter box if you don'r
    want to buy a manual transfer switch.
  11. Unfortunately, a lot of people die from shoddy and illegal wiring over here
    too :-( You should see some of the reports we get from Insurance
    Companies - it's amazing the things people will try to get away with.

    ...but the "line in the sand" is drawn pretty close to the incoming supply
    lines and anyone *actually caught* tampering with their utility supply is
    drawn slowly over hot coals by the Utility first and everyone else second..

    On the positive side, they only do it once.

  12. Rob

    Rob Guest

    I would never forget to open the main breaker in this case. Are there people
    out there that would or have? Alos I would block it open via mechanical

    Thanks for beating me up!
  13. I'm sure you wouldn't.. at least not intentionally, and Yes there are.
    Electrical wiring must be safe enough to be fool-proof. If someone else
    decided to hook up the generator whilst you were away somewhere and they
    killed themselves (as they have) you (as the designer/installer/owner) would
    get locked up. How would that make you feel??
    No problem!.. We are happy to oblige. ;-)

  14. Charles,

    Sorry for the belated response. I have not researched the various
    codes. I do not doubt that there may be codes or guidelines that
    suggest, recommend, or mandate double pole - double throw switches to
    connect generators to a customer's low voltage system. In most cases,
    the issue is to prevent damage to the generator itself or the
    associated wiring and equipment in the event it inadvertently attempts
    either to back feed a dead power system or to prevent an out of phase
    synchronization with a live power system.

    While the protection of utility personnel may be mentioned, I do not
    believe that this is a relevant point. My recollection is that the
    OSHA requirement for personnel safety mandates that conductors in a
    system of above 480 volts be tested and grounded before any work
    commences unless hot line techniques are employed. This means that the
    type of switches that a customer may or may not employ for generators
    have no bearing on the safety of utility personnel. In reality, who
    would trust their life to devices where an uneducated customer was
    responsible for the installation and maintenance and which in any
    event have no visible break to allow inspection to insure that they
    are open. We arrange elaborate assurances to confirm de-energization
    for personnel protection with interconnected electric utilities who
    know what they are doing (visibly open switches, locked, tagged,
    grounded, and guaranteed to remain so). Why would any rational and
    competent utility trust an even well intentioned customer with a
    portable generator and a plug or switch?


    John Phillips
  15. Tom,

    I would be interested in any references for your assertion. If any
    utility workers were killed, there has been a huge cover up in the
    electric utility industry where I work. If they were killed, they were
    in violation of OHSHA and most electric utility safety practices that
    require that they treat all conductors of 480 volts or higher as live
    unless they first test and then ground them or use hot line work
    techniques. It is the height of ignorance to assume that any utility
    would rely on an uneducated customer to prevent a back feed from his
    or her generator for the safety of the lives of its workers.

    Please give me some evidence or stop spreading misinformation and old
    wive's tales. I would like more than one instance of evidence since
    you used the plural.


    John Phillips
  16. Beachcomber

    Beachcomber Guest

    We arrange elaborate assurances to confirm de-energization
    I am not familiar with utility practices and have a question about

    Is it typical for a lineman after a storm to restore fuses and service
    disconnects without practicing the safety procedures (testing for the
    presence of voltage, proper gounding, etc.) that you mentioned?

    Improper backfeeding of service conductors is and should be considered
    a crime with severe penalties, of course.

    I'm just wondering if some of the experts in the field would suggest
    that perhaps a change in procedure for utility crews such as
    increasing training to be aware of,and test for, potential backfeeding
    situations might help prevent some of these incidents where a lineman
    was killed or injured. Are you saying that some utilities are
    deficient in this training?

  17. Bob Weiss

    Bob Weiss Guest

    A net-metered RE system must have an inverter/automatic transfer switch
    that automatically disconnects from the grid in the event of a loss of
    utility power. Utilities invariably require an accessible, well labelled
    disconnect outside the house, near the service entrance.

    The utility generally inspects the installation VERY closely before
    allowing you to connect such a system to the grid.

    Bob Weiss N2IXK
  18. If fused disconnect switches are not capable of picking up load, then
    the circuit should be tested for potential before it is closed.
    Recognize that it will normally take a very large generator to be able
    to back feed any section of distribution line. There are several
    houses on the low voltage side of my own 13.8kV to 240 volt
    transformer and my 5kW unit is not capable of back feeding them. There
    are hundreds of houses in the line segment between disconnects.

    John Phillips
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