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Author Topic: neutral ground bonding - using coach to power the house  (Read 17392 times)
Sean
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« Reply #90 on: February 11, 2011, 09:01:39 AM »

  All I can say, is that if after almost 7 pages we dont have a CLEAR and SIMPLE answer... 


Art, I have provided a crystal clear answer that is as simple as possible.  I have written it three different times three different ways because some people want to continue to argue that there must be something easier -- there is not.  I will now write it a fourth time, in numbered order:

1. Isolate the neutrals in your house distribution panel, if they are not already.  Kits are sold in hardware stores for every make and model of panel to do just this; the kit is about $15-$20.  The task is tedious and time consuming but not difficult.  Do it now -- it will be too late when the power outage happens.

2. Install transfer gear upstream of this panel which transfers all hots and neutrals; usually that means three wires or "poles."  This can be a manual switch, an automatic switch, a pair of interlocking circuit breakers, or a junction box with lugs where the wires can be removed to connect to a generator pigtail.  It can even be the original input lugs in the house panel, so long as there is a main lug for the neutral where it can be safely removed.

3. Relocate the house's ground-neutral bond upstream of the transfer gear if it is not there already.

4. Connect the bus generator to the transfer arrangement you installed in step 2.

Done.  Safe, simple, effective, inexpensive.  You ought to be able to do all of this with less than $30 in parts from Home Depot for the pigtail solution; a transfer switch or breakers is more and will depend on the size of your house service.

-Sean
http://OurOdyssey.BlogSpot.com
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Fred Mc
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« Reply #91 on: February 11, 2011, 10:17:02 AM »

"Isolate the neutrals in your house distribution panel, if they are not already.  Kits are sold in hardware stores for every make and model of panel to do just this; the kit is about $15-$20.  The task is tedious and time consuming but not difficult.  Do it now -- it will be too late when the power outage happens."

Sean, can you point us to a website that might have a picture of such a device. It helps when you go to the borg if you kinda have an idea of what you are looking for as they don't always understand what you are talking about.

Thanks
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Fred Mc
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« Reply #92 on: February 11, 2011, 10:23:11 AM »

So just to re-iterate so I have this clear in my mind.

1. I get a kit that allows me to isolate the neutrals in my house panel.
2. I install a transfer switch that switches both hots (but not neutral) from utility to generator i.e. the generator and utility can't both be on at the same time.
3.I hook up my generator that is neutral bonded.
4. The bonding occurs in the generator and not the house panel.

Thanks

Fred Mc.
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Sean
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« Reply #93 on: February 11, 2011, 10:57:17 AM »

...
Sean, can you point us to a website that might have a picture of such a device. It helps when you go to the borg if you kinda have an idea of what you are looking for as they don't always understand what you are talking about.

Here is a photo of an isolated neutral panel:

In the photo, "3" is the ground buss, bonded to the panel.  "2" is the isolated neutral buss, which has a cross-tie to a neutral buss on the other side of the panel for convenience.  "1" is the incoming hot power.

Here is another, smaller panel with an isolated neutral on the lower left, and ground on the right:


A kit for a small load center can be found here:
http://allmmj.com/index.php?option=com_community&view=photos&task=showimage&tmpl=component&imgid=1265&maxW=996&maxH=597

This one has space for eight branch neutrals and the incoming main, so it would be for an 8-space panel.

The isolated neutral buss is usually specific to the make and model of your panel.  You might have to special-order it or go to a supply house, but HD and Lowe's typically carry the ones for the panels that they sell in-stock.

...
2. I install a transfer switch that switches both hots (but not neutral) from utility to generator i.e. the generator and utility can't both be on at the same time.

No, it must switch both hots AND the neutral.  Three poles or contacts in total.

-Sean
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« Reply #94 on: February 11, 2011, 11:17:35 AM »

  Sean

  Ive read what youve written. I am not really arguing it so much as simply giving up on the whole idea. First, In my case I already have $800 into a Transfer switch that does not switch neutrals, there is no kit available to change it, and ill never get my money back out of it. Second, in your own words, 10 out of 12 licensed electricians dont know what they are doing with this kind of hookup. In fact, I doubt many electrical inspectors would approve it no matter how it was done. I know the last one I dealt with got very nervous when I mentioned a standby generator. Third, the place that sold the Transfer switch and builds generators wasnt that familiar with this kind of hookup. And fourth, telling anyone here how to do it could create a very dangerous situation if they do it wrong and they believe you told them how to do it it. It could come back to haunt you. Just saying no, or I dont know, seems the better choice here IMHO.

  That said, I do question the safety of keeping the Bus/RV generator neutrals bonded to the Bus chassis when connected to a home electrical system. If the gen is grounded to the Bus chassis along with the neutral, and the home electrical neutral is bonded to the ground rod in the earth at the main panel, under the right conditions it would seem your body could become a conduit if there is any potential between the Bus neutral and the ground rod. Maybe im just not seeing it right, but im totally uncomfortable with it now. I was thrown hard across a room into a wall once, and landed on the floor completely stunned and with my arm hurting like hell and my fingers burned after getting bit with 120 volts, and my arm hurt for over a year. I have a lot more respect for it now, lol.

  Anyway, I just dont like the whole idea anymore. Generators arent that expensive, and having a real dedicated system for the house with permanent mechanical connections is a better deal anyway.  

  
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Sean
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« Reply #95 on: February 11, 2011, 11:34:43 AM »

... telling anyone here how to do it could create a very dangerous situation if they do it wrong and they believe you told them how to do it it. It could come back to haunt you.

This is the reason that you will never see me suggest anything here that is not safe AND code-compliant.

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That said, I do question the safety of keeping the Bus/RV generator neutrals bonded to the Bus chassis when connected to a home electrical system. If the gen is grounded to the Bus chassis along with the neutral, and the home electrical neutral is bonded to the ground rod in the earth at the main panel, under the right conditions it would seem your body could become a conduit if there is any potential between the Bus neutral and the ground rod.

That is exactly correct.  However, unbonding the generator in the coach has its own dangers (and is against code), which is why I keep coming back to making the proper changes at the house end instead.

I respect your decision to get a proper backup generator so you can protect your $800 investment in transfer gear.  It is ultimately a safer solution anyway.  However, many people are following this thread and if they are insistent on using the bus for backup power, they need to see the right way to do it.

-Sean
http://OurOdyssey.BlogSpot.com
« Last Edit: February 11, 2011, 01:49:17 PM by Sean » Logged

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Tim Strommen
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« Reply #96 on: February 11, 2011, 12:14:36 PM »

Clarity:




...I respect your decision to get a proper backup generator so you can protect your $800 investment in transfer gear.  It is ultimately a safer solution anyway...

I second this...

...That said, I do question the safety of keeping the Bus/RV generator neutrals bonded to the Bus chassis when connected to a home electrical system. If the gen is grounded to the Bus chassis along with the neutral, and the home electrical neutral is bonded to the ground rod in the earth at the main panel, under the right conditions it would seem your body could become a conduit if there is any potential between the Bus neutral and the ground rod...

This is a HUGE reason, that in NEC any exterior mounted/serving outlets SHALL be protected by a Class-A (<6mA) GFCI device between the bond and the outlet!!!  If there turned out to be any potential across the neutral and ground that exceeds 6mA (often they trip as low as 4mA), it would pop the GFCI device and you'd be safe.  What goes out on HOT and doesn't come back on Neutral can be assumed to be returning on Ground due to the bond at the power source (but only with one bond in the system).  I think you're obviously on to the idea for how potentially dangerous this can be.and have the correct caution while approaching it...

...unbonding the generator in the coach has its own dangers (and is against code), which is why I keep coming back to making the proper changes at the house end instead...

I also second this - I would also offer for clarity of those reading this thread, that unless you have properly set up a load (house) to be plugged in to a portable generator - as a general rule, you should not plug your bus generator into the load.  This comment is intended to emphasise that nothing we've stated on this thread suggests that anything removes responsibility from the operator to check that the load they are attaching to is correctly set up for the power source you give it.  Like Sean's earlier comment, a device is safe by "listed" design practices and testing - it is always up to the installer/user to use these things correctly (so don't just plug into a neighbor's generator power input plug without ensuring it is correctly set up...).

{bad_humor}"Guns Don't Kill People, People Kill People With Guns" = "Electricity Doesn't Kill People, Electricians Kill People With Electricity"{/bad_humor}

-Tim
« Last Edit: February 11, 2011, 01:03:36 PM by Tim Strommen » Logged

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