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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 online now
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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 online now
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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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  #25  
Old 04-15-2017, 10:34:07 PM
Steve Dawkins Steve Dawkins is online now
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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
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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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  #27  
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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  #28  
Old 06-11-2017, 03:43:40 PM
nothingbutdarts nothingbutdarts is online now
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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 online now
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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
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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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  #31  
Old 06-11-2017, 04:42:16 PM
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Default Re: Wiring up 6.5NH (Backfeed Discussion)

I think part of the confusion is that what your inspector meant to say is that you must have a floating neutral to avoid dual NEUTRAL paths. You can have as many GROUND paths as you like. The more the merrier.

But remember, BOTH M2 and M3 connect to the neutral, and NEITHER connect to ANY ground at the generator.

Whether or not a ground rod is required is debatable. Not per NEC, AFAIK, but may well be a local requirement. Even if not, it's likely easier to comply with your inspector than fight over something relatively easy to accommodate.

It certainly doesn't do any harm. As far as connecting it, I'll leave that to those with generator specific experience. All the ones I've connected have been with solid wire, but I would think stranded would be better due to generator vibration and movement.

Keith

Last edited by Vanman; 06-11-2017 at 06:43:05 PM. Reason: Removed incorrect information.
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  #32  
Old 06-11-2017, 04:55:35 PM
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Default Re: Wiring up 6.5NH (Backfeed Discussion)

Thanks - that is very helpful and I'll test it all out with a meter before finalizing. Appreciate your input!
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  #33  
Old 06-11-2017, 05:33:21 PM
Kevin K Kevin K is offline
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Default Re: Wiring up 6.5NH (Backfeed Discussion)

The wire you circled in red is NOT the M2 ground. That wire grounds the bottom commutator brush. Two of the commutator brushes are grounded, so you will find a similar wire grounding the top commutator brush.

There are two M2 grounds, which are short wires with push on clips connecting the M2 junction blocks to ground. The M2 brushes are the second from the generator end.
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Old 06-11-2017, 06:51:39 PM
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Default Re: Wiring up 6.5NH (Backfeed Discussion)

DOH! Thanks for straightening me out on that jumper, Kevin. I edited my post, so that I don't lead any future readers astray. :bonk

BTW, remember to check to be sure that there is no continuity between the M2/M3/neutral junction before connecting the wiring to the building. Once the neutral and ground are connected to the building, you will read continuity between neutral and ground by virtue of their connection at the house.

Keith
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  #35  
Old 06-11-2017, 10:42:02 PM
armandh armandh is offline
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Default Re: Wiring up 6.5NH (Backfeed Discussion)

I did this same 6.5-NH install for my daughter [YMMV]
picture of one of the two [parallel] bonding straps that must be removed
https://www.smokstak.com/forum/attac...9&d=1472156024
the other one shared a ground screw with a commutator brush.
be sure the commutator brush is re connected to ground after bonding strap removal.

since I only had to go 20 ft I used 10-3+G

it was my 3rd interlock install
daughters home
current home
previous home

all done live, but I do not recommend that for a noob.
as a teen age noob I ruined a pair of glasses with molten copper splatter.
at 71 YO I'm a bit more careful.

also moving breakers will likely be necessary.
if there are 4 wire lighting circuits, care must be taken to keep
the red and black on opposite legs, or the 2 circuit's common neutral will be overloaded.
all 3 of my installs had such circuits!

6.5 NH works great for my daughter

Last edited by armandh; 06-12-2017 at 08:38:26 AM.
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  #36  
Old 06-12-2017, 10:12:45 AM
Steve Dawkins Steve Dawkins is online now
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Default Re: Wiring up 6.5NH (Backfeed Discussion)

Quote:
Originally Posted by armandh View Post
as a teen age noob I ruined a pair of glasses with molten copper splatter.
I bet you didn't mind wearing glasses after that day. Don't ask me how I know.
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Old 06-13-2017, 07:38:55 AM
armandh armandh is offline
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Default Re: Wiring up 6.5NH (Backfeed Discussion)

Quote:
Originally Posted by Steve Dawkins View Post
I bet you didn't mind wearing glasses after that day. Don't ask me how I know.
yep don't mind it a bit....and
I'll bet, for a similar reason!

after reading the next post I add to similar.....
but much less 115 V 60A fire works.

Last edited by armandh; 06-14-2017 at 06:49:53 AM.
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Old 06-13-2017, 10:26:44 AM
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Default Re: Wiring up 6.5NH (Backfeed Discussion)

Yes sir....the "incident" tripped a 1200 amp, 480 volt main breaker for an asphalt plant where we were adding equipment. I wish they had arc flash suits back in 1984. It would have saved a lot of pain and suffering. I was inside of an orange fireball. Used to curse glasses every day before that. After I saw molten metal embedded in the lenses, I never complained about glasses again.
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  #39  
Old 06-13-2017, 11:54:04 AM
Leon N. Leon N. is online now
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Default Re: Wiring up 6.5NH (Backfeed Discussion)

Anyone who installs multiple earth grounds between a generator and the home is asking for trouble. Unfortunately the item that will take the hit most likely will be the generator.
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Old 06-13-2017, 12:00:09 PM
Vanman Vanman is online now
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Default Re: Wiring up 6.5NH (Backfeed Discussion)

/\ ??? Do tell!

In many cases code even requires them. All they do in this case is reduce the magnitude of local voltage​ gradients in the earth and reduce the difference in voltage between the equipment and ground during a ground fault or a lightning strike. In the latter case, those extra grounding electrodes may well SAVE connected equipment.

Keith
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