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Wiring up 6.5NH (Backfeed Discussion)


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  #21  
Old 04-14-2017, 10:19:23 PM
AppleTech AppleTech is offline
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Default Re: Wiring up 6.5NH (Backfeed Discussion)

Thanks for the detailed write-up! I have #10 (10/4) running from the generator inlet box to the breaker box running to a dual 30-amp breaker. I'm OK getting a grounding rod and installing it at the generator chassis.

In the input box, the ground should connect from gen to box ground and to ground going into neutral bar in the main box? Here's how I'm envisioning the setup based on my understanding.

Also am I modifying the way neutral works in the NH such that it will no longer be able to be used standalone (which is OK)?

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  #22  
Old 04-14-2017, 11:54:53 PM
Steve Dawkins Steve Dawkins is offline
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Default Re: Wiring up 6.5NH (Backfeed Discussion)

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Originally Posted by AppleTech View Post
In the input box, the ground should connect from gen to box ground and to ground going into neutral bar in the main box?

Also am I modifying the way neutral works in the NH such that it will no longer be able to be used standalone (which is OK)?
You are correct, regarding the grounding at the inlet box and the panel. The ground wire in the SOOW cord will effectively ground the generator when the L14-30 connector is mated to the inlet box.

Will you need the NH as a stand-alone generator, or will it be exclusively used as a home standby? If you keep the neutral and ground isolated at the generator, it will be easy enough to tie them together, if needed in the future.

Neutral/ground connections have been a hotly debated issue on this bulletin board as well as many other fronts in the electrical industry. The National Electrical Code is updated every three years. Many changes are initiated because an incident/accident happened. I have seen older standby generators (1980s and earlier vintage) that had a bolt stud factory welded to generator stator, with the generator's neutral leads connected to that bolt along with a lug for field wiring connections. There definitely wasn't any neutral/ground isolation on them.

BTW, nice job on your graphics.
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  #23  
Old 04-15-2017, 12:15:40 AM
AppleTech AppleTech is offline
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Default Re: Wiring up 6.5NH (Backfeed Discussion)

I don't need it as a standalone I was just curious if I'd need to reconfigure it back should I choose to do so - sounds like I do.

Thanks for your advice!
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  #24  
Old 04-15-2017, 02:13:13 AM
Vanman Vanman is offline
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Default Re: Wiring up 6.5NH (Backfeed Discussion)

Steve, is the ground rod at the generator now required even when supplying a building where a main bonding jumper is installed, such as the OP's scenario?

I always thought that the ground rod was only required when the generator has a bonded neutral, and the building served doesn't, or at least that portion served by the generator doesn't and the transfer switch switches the neutral.

Or is this possibly just a local jurisdiction issue?

Keith
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Old 04-15-2017, 10:34:07 PM
Steve Dawkins Steve Dawkins is offline
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Default Re: Wiring up 6.5NH (Backfeed Discussion)

It's probably more of a local jurisdiction issue that morphed out of a manufacturer's installation diagram or recommendation. Some of the local cities wanted to see a ground rod at the generator, and others did not. The inspectors that did want a ground rod just checked to see if it was connected to the base or frame of the generator.

As we know, grounding electrodes (rods or otherwise) are not required for non-separately derived systems. NEC 250-54 does allow for "Auxiliary Grounding Electrodes" to be connected to the equipment grounding system for local earth reference or lightning protection.
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  #26  
Old 06-11-2017, 01:39:46 PM
AppleTech AppleTech is offline
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Default Re: Wiring up 6.5NH (Backfeed Discussion)

So I'm in the process of reconfiguring the generator wiring now so I can hook it up to test. I see there is a bus in the box with two sides - generator winding wiring goes into one and connection wires to outlet and other go through this bus. Is this a fuse bus? Is order important here or should I just reconnect items as described in my graphic above by moving them around this bus?
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Old 06-11-2017, 03:36:12 PM
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Default Re: Wiring up 6.5NH (Backfeed Discussion)

Ok so I determined it is just a connection bus. However my issue is that I'm out of slots. There are four connectors:

M1 -> CB1
CB1 -> Hot Blk out
M4 -> CB2
CB2 -> Hot red out

Does that mean that M2/M3 should just get wired directly in via wire nut to the outbound neutral white? I am supposing the bus is just to minimize wire nut usage?

Or should I skip the bus for the hot leads and just connect winding wires/outbound leads via the in-box CBs?

OK I think I got it. There were just superfuous connections.

Now I've got the following

M1 -bus- CB1 -> outbound hot blk
M4 -bus- CB2 -> outbound hot red
M2/3 -bus- outbound neutral white

OK another question - I seem to have continuity from chassis ground to neutral. My understanding is that per code I need a floating neutral that does not connect tho chassis ground. How do I make this change?

Right now I am:
M1 -> black hot
M4 -> red hot
M2/M3 -> neutral out

If I understand correctly, I need to wire M2 to the outbound ground and M3 to the outbound neutral, as well as ground the chassis with a rod. This will give me a floating neutral, since N and G are only bonded at the main panel bus?
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Old 06-11-2017, 03:43:40 PM
nothingbutdarts nothingbutdarts is offline
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Default Re: Wiring up 6.5NH (Backfeed Discussion)

Pull the brush access strap off the gen. end, you will see where I believe two A/C brushes have a strap tied to the bell housing, unbolt those to remove ground if that is what you need to do.
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  #29  
Old 06-11-2017, 03:44:28 PM
Vanman Vanman is offline
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Default Re: Wiring up 6.5NH (Backfeed Discussion)

M2 and M3 must be wired together and​ to the neutral only.

The equipment grounding​ conductor (from​ the house) connects to the chassis as does the grounding electrode conductor. Neither to any M terminals.

Keith
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  #30  
Old 06-11-2017, 04:17:15 PM
AppleTech AppleTech is offline
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Default Re: Wiring up 6.5NH (Backfeed Discussion)

Quote:
Originally Posted by nothingbutdarts View Post
Pull the brush access strap off the gen. end, you will see where I believe two A/C brushes have a strap tied to the bell housing, unbolt those to remove ground if that is what you need to do.
I will check this out!

Quote:
Originally Posted by Vanman View Post
M2 and M3 must be wired together and​ to the neutral only.

The equipment grounding​ conductor (from​ the house) connects to the chassis as does the grounding electrode conductor. Neither to any M terminals.

Keith
OK. However as current there is continuity from M2 to chassis ground. My understanding was that the M2 (generator ground, not chassis ground?). Do I need to remove the internal grounding strap to isolate chassis (12v) and generator (120v) ground locations?

This appears to be the grounding strap in question. Removing this would isolate the neutral to M3 and the chassis ground to M2?



---------- Post added at 02:56:00 PM ---------- Previous post was at 02:54:04 PM ----------

Ignore my second note above - I was confusing neutral and ground... my head is spinning.

---------- Post added at 03:17:15 PM ---------- Previous post was at 02:56:00 PM ----------

OK let me retype this. I need to get subscription so I can edit. Sometimes I type faster than I think.

Removing the internal strap will separate the neutral from the generator chassis ground, right?

Then wire M2 (generator ground) to ground run which will meet at the primary neutral bar

Then wire M3 (generator neutral) into neutral run to primary neutral bar

The one piece I'm missing is how to ground the generator to the localized grounding rod. There will still be continuity between ground wire and generator ground, right? If I ground this via ground rod, won't I have the code issue of dual ground paths? I'm just confused because the inspector said I needed to have a floating neutral to avoid dual ground paths - the system is supposed to use the grounding at the main panel. However he also said I should have a ground rod at the generator. Don't these statements contradict or am I missing something?
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