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Author Topic: neutral ground bonding - using coach to power the house  (Read 16032 times)
buswarrior
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« on: February 01, 2011, 04:29:02 PM »

continuing from a diversionary thought in another thread...

Generators compatability with computer?Huh??
http://www.busconversions.com/bbs/index.php?topic=18838.0

I am a big fan of designing the coach conversion for redundancy, and we have the opportunity for that to extend beyond the coach.

If we are thinking of using the coach as back-up power for the house...

There are neutral ground bonding issues to consider, in order that electrocution hazards are not added to the crisis of lost utility power.

May we have some examples of the conditions that would endanger if the neutral ground is present in both the house and the coach?

What strategies, complex to simple, expensive to inexpensive, might we use to SAFELY accomplish this worthy goal of using our perfectly good generator in the coach to maintain our self-reliant selves inside the bricks and mortar alongside?

happy coaching!
buswarrior
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eddiepotts
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« Reply #1 on: February 01, 2011, 04:34:09 PM »

Remember to disconnect the wires from the house so you don't kill the line workers or send power to your neighbors.
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Melbo
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« Reply #2 on: February 01, 2011, 04:43:26 PM »

A sub panel in the house with no connection to your electric system powered from a "buddy outlet" on the coach would be the safest and simplest solution to my way of thinking.

It could run from the inverter or genset and have a gang of outlets that are readily available for what ever you need to plug in in the house

Properly wired it would be safe and isolated from your normal household power grid

HTH

YMMV

Melbo
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Sean
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« Reply #3 on: February 01, 2011, 04:52:27 PM »

...
May we have some examples of the conditions that would endanger if the neutral ground is present in both the house and the coach?


In the simplest terms, since the neutral and grounds are connected at both the generator and at the main panel, then the return current will be divided among those pathways between those two points.  If you had, say, two #8 wires for ground and neutral, then about half the current will travel on each.  But if you use, say, metal clad cable, then a good portion of the return current will actually travel on the jacket.  This presents a shock hazard to anyone who comes in contact with the jacket.  Since the ground points at both ends are likely interconnected through many means, lots of things can become "hot" this way, including the bus chassis and the house panelboard.

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What strategies, complex to simple, expensive to inexpensive, might we use to SAFELY accomplish this worthy goal of using our perfectly good generator in the coach to maintain our self-reliant selves inside the bricks and mortar alongside?


The most straightforward is what I suggested in the other thread: connect your fridge, computer, etc. directly to the bus power system using extension cords and/or plug strips.

The alternative is to completely isolate the ground from the neutral at one end or the other.  In a house, this would mean adding an isolated neutral bus to the main panel, then ensuring that the feeder to this neutral is completely disconnected from the mains (as should also be the hot wires) when feeding from the generator.

Alternatively at the generator end, remove the ground/neutral bonding strap inside the generator's wiring box.  However, the generator then must be also physically disconnected from the bus's systems while powering the house, lest there be a potential for a completely unbonded system when finished.

Both of these latter methods involve a level of risk, in that forgetting to put things back the way they ought to be can create an extreme hazard.  For this reason, I recommend the simpler extension-cord method, or else buy a proper backup generator for the house.

HTH,

-Sean
http://OurOdyssey.BlogSpot.com
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Sean
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« Reply #4 on: February 01, 2011, 04:56:19 PM »

A sub panel in the house with no connection to your electric system powered from a "buddy outlet" on the coach would be the safest and simplest solution to my way of thinking.

It could run from the inverter or genset and have a gang of outlets that are readily available for what ever you need to plug in in the house

Properly wired it would be safe and isolated from your normal household power grid


Such a system is not allowed by code.  Any permanently attached/installed electrical panels and receptacles must also be permanently grounded.  There are obvious safety risks in having a completely ungrounded electrical distribution system permanently installed.

The only sort of distribution system that is both safe and legal in such a circumstance is one that is "temporary" as that term is defined by the code.  Nothing may be permanently affixed or secured in such an installation.

-Sean
http://OurOdyssey.BlogSpot.com
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robertglines1
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« Reply #5 on: February 01, 2011, 05:05:57 PM »

I had a friend with local power utility fix mine up I just pull the main and plug bus into welder outlet and all is good. I to was concerned with hurting someone with back feed or mixed up ground. Last time the house was plugged into the bus for 2 weeks.he fixed the main disconnect so it cut hot lines and ground. then house was plugged in like a extension cord.Have used several times and no shocks or back feed to grid.
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Sean
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« Reply #6 on: February 01, 2011, 05:39:28 PM »

I had a friend with local power utility fix mine up I just pull the main and plug bus into welder outlet and all is good. I to was concerned with hurting someone with back feed or mixed up ground. Last time the house was plugged into the bus for 2 weeks.he fixed the main disconnect so it cut hot lines and ground. then house was plugged in like a extension cord.Have used several times and no shocks or back feed to grid.


I'm sure you meant to say the disconnect cuts the neutral, not the ground.  The ground must never, ever be broken.

That said, I have to say this is incredibly dangerous as well as illegal.  On top of the double-bond problem I have already described, backfeeding any system through a female receptacle is never allowed and is, frankly, playing with fire.  And should your main disconnect ever be accidentally re-engaged while your generator is connected, you could, indeed, kill someone.  At best, you'll overload your generator as it desperately tries to power the whole neighborhood.

Please, folks, let's be smart about this:  it is against the law for a reason, and that reason is that people get KILLLED this way.

If you really want to power your house with your bus generator, then fix the double-bond problem and get yourself a proper generator connection with fail-safe transfer mechanism.  It's required by law, and, sheesh, they're just not that expensive.

-Sean
http://OurOdyssey.BlogSpot.com
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« Reply #7 on: February 01, 2011, 05:43:24 PM »

In your newer houses, the neutral bar is isolated from your panel and your grounds. That is if they were inspected when built. But you never really know what someone did in your house.
I am with Sean on this one. Use extension cords or a separate generator. You should also install one of these http://www.northerntool.com/shop/tools/product_200196624_200196624#

Gary
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« Reply #8 on: February 01, 2011, 05:50:22 PM »

In your newer houses, the neutral bar is isolated from your panel and your grounds. That is if they were inspected when built. But you never really know what someone did in your house.

I would have to go take my panel cover off to be sure, but I recall that the neutral and ground are bonded in my house main panel.  My house was built in 2001 per code and was fully inspected.  I did all my own wiring with a little help from my father.
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« Reply #9 on: February 01, 2011, 06:05:05 PM »

Since neutral bonding is suppose to be at a single location, when using my generator to power my house I disconnect the generator from the bus and remove the neutral grounding at the generator. The main circuit breaker on the house panel is turned off and the unbonded generator is back feed into the house panel. Neutral grounding is done in the house panel. Most home panels share the same terminals for both ground and neutral wires making it difficult to isolate neutral to ground bonding. With this configuration the generator is completly disconnected from the bus and neutral bonding is done in the house panel.
When reconnecting the generator to the bus, the neutral bonding at the generator is reconnected. Kenny
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Sean
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« Reply #10 on: February 01, 2011, 06:06:23 PM »

In your newer houses, the neutral bar is isolated from your panel and your grounds. ...


Actually, in most jurisdictions, the neutral and ground bus will be one and the same in the main panel, even in brand new construction.  Sub panels, however, will have a separate, isolated bus for neutrals.

There are some jurisdictions that require an isolated neutral bus in the main panel, with the bond at the service entrance where the meter is located.

-Sean
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« Reply #11 on: February 01, 2011, 06:14:37 PM »

Other than getting electrocuted, is there a way to test to make sure the system is safe i.e. when the bus generator is separated from the bus and plugged into the house? Can you use a meter to test?
Thanks

Fred
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« Reply #12 on: February 01, 2011, 06:17:29 PM »

Y'all are really confusing me!  Huh  I wish Cody were here to help decipher it all out! Wink
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« Reply #13 on: February 01, 2011, 06:33:50 PM »

If any of you have ever faced the fact that you will not have power for many days much less the fact that your business's will not have power for possibly 3 weeks you will soon learn that codes are no longer in play. As with many things in life some common sense takes front and center. I had 4 generators running for several weeks, a fuse panel that only I could understand now and every generator well grounded to the ground besides to the panels at my shop. It was that or no heat, no money and a lot of other serious issues. I back fed my house through the dryer with the generator. Others did it through the heat pump. Breakers work in either direction! You do what you have to do. I did and the biggest hassle was getting fuel to run them when there was no power to the fuel pumps!
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« Reply #14 on: February 01, 2011, 06:45:46 PM »

In Alaska they have made us isolate the neutrals from the grounds for 15+ years now. I do know that other jurisdictions have different codes. Not only that, even in my state you never know if someone connected a neutral to a ground in a light box someware. This is why I don't recommend connecting the bus to the house, because you just never know.

I am really glad this thread was started, lots of good information. I know a few people here that has been wanting to do this. We have power outages all the time from storms and beetle kill trees falling on lines.

Gary
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