NEMA L14-30, Purpose of neutral in circuit (4 vs 3 prong)

Post in 'DIY and General non-hearth advice' started by g1mb, Dec 13, 2011.

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  1. burnham

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    I am a lineman and a master electrician. Your 4k generator could excite the coil in a transformer and send primary voltage out of the primary bushing. You don't have to backfeed the entire grid if a wire is broken, or a fuse is blown. Maybe you know what you're doing...maybe you don't. Maybe you just think you do.
     
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  2. nate379

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    Sure. I know to turn OFF the main and it's fine. It's just like wiping my ass after I chit, not something I forget.
     
  3. velvetfoot

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    Isn't bonding of neutral and ground only supposed to occur in one place, like the main panel?
     
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  4. BrotherBart

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    Personally I don't post my illegal activities on public Internet sites until a long time after the statute of limitations has run out.

    Prosecutors use Google too.
     
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  5. bubba3228

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    When I took my apprenticeship the State of Wisconsin head inspector visited our class, he explained to us, the statute of limitations for murder is 7 years. There is NO statute of limitations for anything I am responsible for installing. I take my profession very seriously.
     
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  6. nate379

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    I torn the tag off my pillow and went 3mpg over the speed limit today... please come arrest me. ahahahahaahaha!
     
  7. oldspark

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    This thread is out there orbiting the earth now, and it aint comeing back soon.
     
  8. jharkin

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    A lot of arrogance on this thread. I'm no master electrician but I know enough from reading that I can tell folks are doing things over their head here.

    Somebody IS going to get hurt. When that happens and you go to JAIL don't say we didn't try to warn you.

    g1mp - It seems like you are still not grasping a critical concept. Ground x= Neutral. A neutral IS a current carrying conductor, its just biased to zero volts. a loose connection in the wrong place can put that at full line voltage. Thats why the old 3 wire dryer outlets are no longer legal for new installs -they were using the bare wire as the neutral current carrying conductor. It was an old exception that is no longer allowed for good reason.

    NATE379 - I checked you are right that you can still buy 3 prong 240v outlets - misstatement on my part. I'm still fairly sure that current code does not allow piggybacking of ground on the neutral for any new installs (our resident electricians should confirm).

    velvet - Yes you are correct the neutral should only ever be bonded in one spot. Bonding in multiple places creates multiple paths and the potential for neutral current to follow the bare ground - again leading to the risk highlighted above. It is for this reason that when you use a generator feeding a main or transfer switch via a 4 wire (hot/hot/neutral/ground) you are supposed to break the bond of ground and neutral at the generator end.

    Finally... For anyone who thinks they are so perfect they will never forget to kill the main. What happens when the power goes out in the middle of the night in pouring rain and your basement floods and you are frantically rushing, half asleep, to get that generator up and running to restart your sump pump. Ive been in that exact situation. Walking through an inch of water to hookup extension cords. Not fun or safe. I can tell you I would forget in spite of my best intentions. Maybe you are much more careful than me but I just cant stomach the risk. You don't even need an expensive transfer switch. A simple $50 interlock breaker will do it. You have a lot more than $50 into the generator.
     
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  9. gpcollen1

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    I think those of us responsible DIYers back feeding our panels are very careful and always open the Main Breaker. The problem with discussions like these is that someone who knows nothing, like half the people buying generators out there in the past 2 months in CT for sure, could very well forget the open the Main Breaker. I would not forget even with a foot of water int eh basement, which is impossible at my house anyway.
     
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  10. hemlock

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    Suppose someone else (friends/visiting family, etc..) closes the main trying to "help"? I've learned from years in industrial repair that some people just like flicking switches. I'm not suggesting my little set-up is perfect, but I'm not back-feeding to the grid - which is precisely why I built my panel. I'm not trying to come across as critical - but there's mistakes, and then there's mistakes , and one like this could be life-changing. I'm no electrician, but I've worked around it enough to have a huge respect for it.
     
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  11. oldspark

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    Well I am (was) an electrician, industrial type and when ever some of these posts come up I do some research and usually learn a few things, one of the best things I have learned is NOT to give advice about wiring on a forum, you never know how much the other guy knows so its hard to cover all the things that can go wrong. There are so many varibles that change what you need to do, hooking up a gen in one of them, I would never cut the neutral off and not use it (think some one did that) electrical is easy to learn but not over night. So much good information on the net these days no need to ask joe blow for info, do your own research and if you dont understand some thing hire it done. Rambling now :sick:
     
  12. gpcollen1

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    I agree to an extent BUT there are very simple devices out there that can keep people from closing the main. I am still working on what my final system will be. for now, it is manual.

    http://www.seton.com/no-hole-circuit-breaker-lockout-js171.html

    http://www.grainger.com/Grainger/BRADY-Blocking-Bar-Lockout-Kit-3LY22?Pid=search
     
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  13. g1mb

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    For the record: I understand the difference between the ground and neutral circuits. I never had any intention of using the ground (bare wire) to carry current. I referred to the neutral wire on my 3 prong dryer outlet as ground because in an older 240 system I wouldn't have referred to it as a neutral per se.

    I'm not going to get into a shouting match over back feeding an outlet as I am actually on your side of the issue. But If I were to backfeed this 3 prong dryer outlet from my generator I would be backfeeding 2 hots legs and 1 neutral through a 10/3 cable to the main panel. No bare wire involved. As far as the bonding issue, even though the neutral and ground are bonded in my generator, I would not be bonding them in the house because I would be feeding a 3 prong receptacle, and not a 4. If I were to backfeed a 4 prong (newer) receptacle with this generator as is, I would most certainly be creating a bond between the neutral and ground circuits in the house.
     
  14. Vermonter2011

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    Six Dangers of Backfeeding Through The Dryer Outlet: http://www.qsl.net/kc5qhh/backfeeddangers.pdf

    One thing that people haven't mentioned here (maybe I missed it) is that if you are backfeeding through your dryer outlet and you leave the main open, the power company can fry your generator, your wiring and/or all kinds of stuff throughout your house. They also will intentionally fry any generator that is live on the line, to protect their personnel.

    So not only is there a risk of injuring a lineman, but there is also a risk that your property can be damaged if you leave the main open.
     
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