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Thread: Backfeeding question

  1. #31
    DIY Senior Member guy48065's Avatar
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    Quote Originally Posted by jwelectric View Post
    Nothing hard about it at all.
    Certainly--but I just wanted to SEE how yours looks.
    Romeo and Atlanta, MI

  2. #32
    Jack of all trades DonL's Avatar
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    Quote Originally Posted by guy48065 View Post
    Certainly--but I just wanted to SEE how yours looks.


    That is what I told Her...
    Theory only works perfect in a vacuum.

    Cyber Security Protection for Windows C:\ > WWW.WinForce.Net

  3. #33
    General Engineering Contractor ballvalve's Avatar
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    Quote Originally Posted by jwelectric View Post
    Once upon a time there was a man who liked to play with Crocodiles but he is no longer with us, Steve Irwin.

    So my advice is to either do things in a safe manner or look forward to meeting Steve. Playing with danger such as described above is a sure way to join the un-living.
    If you know the rules of elecricity, it does not bite, unless you goof bad. My crocodile wont bite because its a female plug, and the pump has a small breaker panel. then use a pigtail with double male ends to make the dead connection. turn off pump with lever on pressure switch, start genset and turn lever on.

    That Aussie had a big screw loose. should have been in the circus.

  4. #34
    General Engineering Contractor ballvalve's Avatar
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    Quote Originally Posted by guy48065 View Post
    Oh I bet there are many more hair-raising setups that no one will admit to. 10 years ago I had AC installed and the installer got into my meter box for some reason. Since then the little lock wire has been visibly and obviously cut and in over 100 visits by the "meter reader" it's never been replaced.
    Soooo...when I backfeed my house I pull the meter and connect the genny cord right to the bottom meter lugs. Works for me until such time that I replace my panel.
    the code gestapo would really love to find that! I had a meter in the absolute middle of nowhere where I worked a vineyard. No meter for years, no cover and hot terminals. I just made a jumperset to irrigate the well. Another property had a hot open meter socket for 32 years. Some 6th sense told me to test it before playing and inded it was hot. Could have had a 32 year pot grow there for free. Our utility is pretty lax in these VERY rural areas. for instance, the power to my house comes down a steep canyon with the crossarms attached to pine trees. [1996!] The tie back for the final pole is drilled into a large oak tree.

  5. #35
    DIY Senior Member kcodyjr's Avatar
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    Re: backfeeding. Please, pretty please, with a cherry on top, don't. Just don't.

    I'm not licensed for current carrying wiring, but I am comfortable with the science, and do have professional experience with data wiring, several types of audio, and some endpoint telecom stuff. The theory crosses over completely, even if the installation codes don't at all.

    Given a suitable ground, all you need to carry current is one wire. See earth-return systems. Main breakers do not disconnect the neutral; therefore you have the one wire. Not all installations bond the neutral and ground at the panel and even if it does, residential ground rods often make a lousy connection to the earth. So, don't count on the neutral being electrically clamped to ground. Think of it as essentially hot; it can become actually hot under some non-fault conditions; not full voltage, but enough to bite.

    Something often missed about electric circuits is that, in any series circuit, the current is identical throughout the circuit at any given time. Or, in layman's terms, what goes in must come out. If you're drawing 20A at 240V, there's 20A coming through each pole of the breaker. If you're drawing 10A at 120V, there is 10A going through the hot and 10A going through the neutral. It isn't just waste or spill being sent down the neutral; it's not like a pipe delivering electricity to you. It's more like sticking your hand into a river. If it wasn't all flowing past you, there'd be no pressure on your hand.

    Consider the circuit again with that in mind.

    Generator sends +/- 120 into the panel, some of which goes straight through as 240V, some lesser amount coming back along the neutral as 120V. Neutral is therefore no longer at ground potential, to some greater or lesser degree. However, neutral is touching someone else's loop and able to exchange electrons with it.

    Imagine a stream running within inches of the mighty mississip. Now imagine the river drying up, to simulate the power outage. Now knock down the separating wall, and observe insignificant, but nonzero, amounts of the stream leaking out into the riverbed.

    Now, restore the river, and stand the hell back. What just happened to your generator and anyone standing near it?

    Clearly, this doesn't happen every time someone does this, but it can if conditions line up right.

    If you really must use the house wiring to supply your key appliances from a generator, here's my suggestion. It probably isn't code, but I'm perfectly comfortable asserting that it's safer than what you're doing.

    Install a small main-lug subpanel next to your existing main breaker panel. Move all those key circuits over to it.

    Instead of hard-wiring the subpanel, connect it via a 3-wire-plus-ground plug and receptacle to the main breaker panel. Also connect a hardwired ground between the two. (BUT NOT NEUTRAL!)

    Then, when the power goes out, fire up the generator, drag its extension cord down to the basement, and plug the whole subpanel into it.

    Then, when the power comes back on, there's absolutely no cross connections and no safety hazard. Stop the generator, plug the subpanel back into its dedicated outlet, and close its feeder breaker in the main panel.

    Let's describe this as "specialty manual transfer switch, at the end of your arm." All organic, fully green technology.

    Guys, if that idea is in any way actually viable, please modify for code compliance...

  6. #36
    DIY Senior Member guy48065's Avatar
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    Now, restore the river, and stand the hell back. What just happened to your generator and anyone standing near it?
    Nothing because I'm not connected to the grid. You can't get any more positively, verifiably UN-connected than to pull the meter.
    Romeo and Atlanta, MI

  7. #37
    DIY Senior Member kcodyjr's Avatar
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    DonL, I would certainly assume so, but I can't claim to know the code.

    I wouldn't necessarily assume the ground conductor goes to the pole, though. I've never seen more than three where the pole lines hit the house around here, although my MH uses a four-conductor connector to a ground rod next to a multi-meter mast. However, if one is going to use in-house wiring AT ALL then the ground conductor has to be accounted for. It'll be bonded to the panel and, hopefully, to a ground rod right outside or to the footings' rebar or both.

    Does one really drive a ground rod in when using a portable generator? I've never seen anyone bother... and it seems to me, better off using the house's ground rod than none at all.

    I don't see a problem with the mains neutral being bonded to the same ground rod via the panel, though. There will only be current present during fault conditions, so the neutral won't be seeing a potential. Just to drive it in again, I do see a problem with putting steady potential on that same point in the panel via the in-house neutral conductor, which is why backfeeding without a true mains disconnect is always stupid.

    Come to think of it, that same MH connector would be suitable for what I suggested, and you wouldn't need to hardwire ground, assuming the generator really does have its own ground rod.

  8. #38
    DIY Senior Member kcodyjr's Avatar
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    Quote Originally Posted by guy48065 View Post
    Nothing because I'm not connected to the grid. You can't get any more positively, verifiably UN-connected than to pull the meter.
    I've actually never seen one off. Do they indeed disconnect the neutral as well?

    If so, then safety problem mitigated, unless the power company guy sees it. It'd be a world of hurt playing with meters around here.

  9. #39
    Jack of all trades DonL's Avatar
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    Quote Originally Posted by kcodyjr View Post
    Given a suitable ground, all you need to carry current is one wire. See earth-return systems.

    That may be true if the Voltage is high enough, but for 120 or 240 VAC , It will not work in any earth resistance that we have in the USA. For HV distribution it works fine, but a loose Transformer ground can kill you.


    A couple ohms of resistance makes a big difference on low voltage like 240 VAC.
    Theory only works perfect in a vacuum.

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  10. #40
    Retired Defense Industry Engineer jadnashua's Avatar
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    Ground is for safety to provide a path to trip the breaker or fuse or help bleed off induced voltage from a storm. The fact that neutral is bonded to ground is a useful thing, but is not required except for that safety issue (which is big, though). If your loads are balanced, any current in the neutral line back to the transformer is minimal to nothing, but in a 110vac circuit, it is whatever is coming out of the hot lead, at least until it gets back to the panel. So, while neutral may have a low voltage to ground, it still can carry a lot of current and this is potentially dangerous.

    Once repaired HV power supplies while in the Army...the filament voltage was only 5vdc, but since the cathode might have been at 5K volts, it couldn't actually be 5vdc to ground or things would arc and burn up...it was 4,995vdc to ground. It all depends on what your reference point is...

    Point of all this is that the neutral can and often does have current running through it and it is not insignificant. Mess with things, get a loose connection, or take things off, and rearrange them, and it can be very dangerous. The fact we take these things for granted is where you can get sloppy, and create a very bad situation. The codes are written for those 'what if' situations, to try to keep people safe. Messing with them can put not only you, but your property and others in mortal danger. If you don't know what you are doing, or can't do it per code, you probably should not be doing it.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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