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Generator & Transfer Switch Issue Solved-Metal Building To Ground or not?

Generator & Transfer Switch Issue Solved-Metal Building To Ground or not?

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  #1  
Old 04-25-16, 05:58 PM
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Generator & Transfer Switch Issue Solved-Metal Building To Ground or not?

For a short recap:

I have a Gentron (Sam's Club) 8KW running (10KW peak) generator that does not have GFCI breakers, but neutral is bonded to the frame.

I decided not to do a transfer switch, and instead, the 4 circuits that need to be powered during an outage will have a plug on them. They will plug into a receptacle that is powered from the utility, and when needed, switched to a receptacle powered from the generator. The generator is attached to a 7' copper grounding rod (I tried to push it in with a bucket of a tractor and bent it).

I have a NEMA 14-30 plug at the generator, and 40 feet of 4 conductor 8 AWG SOOW cable.

So, the way I interpret NEC states that since it is a separately derived system, the neutral in the main panel should not be bonded to ground.

But I feel that the steel that composes the outside of the building should be bonded to:

Ground? or
Neutral?

The building itself should not have a ground rod attached, correct?

Should the metal of the building become energized, I only need 1 path back to the source, which would be the neutral or ground in the SOOW cable. If the building were grounded, there could potentially be multiple paths?

Am I right?

and if the building should be bonded to the ground? or neutral of the SOOW cable, what is the best way to do this?

Thanks In Advance

Walter
 
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  #2  
Old 04-25-16, 07:13 PM
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The generator is never connected to the house system (except via equipment grounding conductors and/or grounding electrode conductors). So no changes are needed at the main panel.

The circuits eligible to receive generator power are disconnected from the house system (via unplugging) and connected to the generator (plugged in there instead).

The 7' ground rod no longer qualifies as a grounding electrode but can be left in place. Still, if the ground rod is at the foundation, it should have a #6 copper wire bonding it to the nearest pre-existing ground rod for the building.

One spot on the building shell should be connected to the main panel back, to the main panel neutral bus, to a pre-existing ground rod with all 8' in the ground, or somewhere along the #6 copper wire connecting those last two items.

Don't forget, the cable that is plugged into the generator must first feed a subpanel if more than 20 amps are involved. Ordinary receptacles further downstream must have overcurrent protection (fuses or breakers) of 20 amps or less.
 

Last edited by AllanJ; 04-25-16 at 07:29 PM.
  #3  
Old 04-25-16, 07:56 PM
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You said that the generator is never connected to the house system (except via equipment grounding conductors and/or grounding electrode conductors). So no changes are needed at the main panel.

The circuits eligible to receive generator power are disconnected from the house system (via unplugging) and connected to the generator (plugged in there instead).

The 7' ground rod no longer qualifies as a grounding electrode but can be left in place. Still, if the ground rod is at the foundation, it should have a #6 copper wire bonding it to the nearest pre-existing ground rod for the building. All ground rods for the building must be so bonded.

One spot on the building shell is bonded to the electrical ground which is the panel neutral bus. The actual attachment point could be any one of: the main panel back, the main panel neutral bus itself, a ground rod with all 8' in the ground, or to one of the #6 (sometimes #4) copper wires coming from the panel and going to ground rods or to a cold water pipe exiting the house underground .

Don't forget, each cable that is plugged into the generator must first feed a subpanel if the cable will carry more than 20 amps. Ordinary receptacles further downstream must have overcurrent protection (fuses or breakers) of 20 amps or less.
 
  #4  
Old 04-25-16, 08:17 PM
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I always try to include as much information as possible, but I have missed a couple of points.

The 7' copper ground rod is at the generator, 40' away from the building, and connected by an approved ground rod clamp to #4 bare copper. So if I understand correctly, I need a full 8' copper rod buried in the ground. Does it need to be any amount of distance from the 7' rod? I have read something about ground rods being at-least 8' apart.

Then I just make sure that the panel [for the generator] (with a 30 amp main breaker and 2-15 amp breakers and 2-20 amp breakers) is bonded to the metal shell of the building, which I assume can be with sheet metal screws?

Reading one of your sentences make me believe I need to install the panel bonding screw, which then provides the bond between the panel neutral and panel ground. This is the part that confuses me.

Thanks for your responses. I just don't want someone leaning against my building, in the rain, to even have the chance of being shocked.

If
 
  #5  
Old 04-25-16, 08:22 PM
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I though generators were not normally connected to a ground rod except when there was no alternate power supply such as generators on construction sites?
 
  #6  
Old 04-25-16, 09:07 PM
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This generator (GG10020) has 4 NEMA 5-15 receptacles (2x2), a NEMA L5-20 and L14-30 receptacles. There are 2 20 amp breakers and a dual pole 30 amp breaker. There is also a ground bolt and the manual states "The generator must be earth-grounded for fixed installations in accordance with all relevant
electrical codes and standards before operation."
 
  #7  
Old 04-26-16, 05:52 AM
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The "main" panel I was referred to is the panel with the first whole-house disconnecting means which may be a breaker set or just a plain (large) switch. The panel bonding screw or strap from neutral bus bar to the panel back should have already been installed there. This is where the fat ground wires (grounding electrode conductors) I referred to should enter.

With the generator and its ground rod(s) several to many feet away from the house, you do not need to run a fat (#6) wire from that ground rod over to other ground rods against the house. The generator will work just fine with just the 7' ground rod (or no ground rod at all). I am not sure whether the NEC specifies you need two ground rods fully 8' long or at least one ground rod fully 8' long at this generator. When two ground rods are required for a building (usually the case) the rods need to be at least six feet apart.
 
  #8  
Old 04-26-16, 07:04 AM
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For a panel mounted on the wall and that is energized only using a cord that may be plugged into a generator out in a field or plugged into a building receptacle, treat it as the first panel in a shed or outbuilding. It's a subpanel; the bonding screw or strap from its neutral bus to its back or other grounded parts must not be engaged.

Include a #6 ground wire from the panel ground bus or panel back over to the existing ground rod(s) for the building. There must still have a ground wire (equipment grounding conductor) in its cable or connection to its power source.
 

Last edited by AllanJ; 04-26-16 at 07:42 AM.
  #9  
Old 04-26-16, 11:15 AM
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I have attached a diagram of my setup. I have included the Letters A, B,C,D and E.

Please, connect the dots for me (A connects with _, but not with _) and then I can use the posts to understand what, why, how and when
 
  #10  
Old 04-26-16, 11:28 AM
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In the main panel, A & C both land on the shared ground/neutral bus (B) which is also connected directly to the metal panel box through the bonding screw or similar metal-to-metal mount. There should be a four wire feeder between the main panel and the generator panel (hot, hot, neutral & ground). The neutral from that feeder lands on the ground/neutral bus (B) in the main panel and on the isolated neutral-only bus (D) in the generator panel. The ground from that feeder lands on the ground/neutral bus (B) in the main panel and on the ground bus (E) in the generator panel which should also connect to the metal panel box itself.
 
  #11  
Old 04-26-16, 12:03 PM
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Im not an electrician but am a plumber/pipefitter for generator installs in my company..

From watching the electricians 2- 8 ft ground rods are driven in the ground 6 ft apart.. This they do when the existing ground rod cant be found or is questionable.. Or they add another 6 ft from the existing..

We install generacs and kohlers...

As far as the neutral, all the gens I see from the 8kw's to the 48 kw's we install have a floating neutral... The bond is made when the auto transfer switch, switches over to gen power.. ( I believe)

I know that the electricians often do a power swap where that take the mains out of the main panel and put them to the transfer switch..

Again these are just my observations.
 
  #12  
Old 04-26-16, 12:11 PM
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Oh lolol.. The gentran is a portable... Ignore my post below..

 
  #13  
Old 04-26-16, 12:12 PM
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I decided not to do a transfer switch, and instead, the 4 circuits that need to be powered during an outage will have a plug on them. They will plug into a receptacle that is powered from the utility, and when needed, switched to a receptacle powered from the generator. The generator is attached to a 7' copper grounding rod (I tried to push it in with a bucket of a tractor and bent it).
I dont think you need the ground rod.. The generator is a seperatly derived system...
 
  #14  
Old 04-26-16, 12:20 PM
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Portable generators are covered in Section 250.34 Portable and Vehicle-Mounted Generators. This section allows the generator or vehicle frame to serve as the grounding electrode when:
(1) The generator supplies only equipment mounted on the generator, cord-and-plug-connected equipment through receptacles mounted on the generator, or both, and
(2) The non–current-carrying metal parts of equipment and the equipment grounding conductor terminals of the receptacles are bonded to the generator frame.
IMSAjournal.com .
 
  #15  
Old 04-26-16, 12:56 PM
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I don't have a transfer switch. The protected circuits have a plug on them. I will switch the plugs from the dedicated receptacles wired to the utility panel to the other dedicated receptacles wired to the generator panel. When utility restores, I unplug and re-plug.

They are 2 completely separate panels. No shared circuits.
 
  #16  
Old 04-26-16, 01:49 PM
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Your equipment now is plugged into utility supplied outlets,when utility fails you remove the plugs and plug them into the generator,I don't see the problem,but what are you using the #8 cable for?
 
  #17  
Old 04-26-16, 02:39 PM
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2 Panels, 2 sources for electricity, no transfer switch. The 8/4 SOOW is from the generator to a dedicated panel for loads for the generator

Utility Load Generator
| | |
| | |
| | |
|-------Outlet U1 |--> Outlet G1---------|
Above: Load powered from generator

Utility Load Generator
| | |
| | |
| | |
|-------Outlet U1 <--| Outlet G1---------|
Above: Load powered from Utility

Load has a cable, which can be plugged either to the utility powered outlet, OR the Generator powered outlet.

No switching of L1, L2 or Neutral
 
  #18  
Old 04-26-16, 07:06 PM
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I read it this way, "Your equipment (the right panel which in turn feeds receptacles) is plugged into a utility supplied outlet, when utility fails you remove the plug and plug it into the generator."

The #8 SOOW cable is what is attached to the aforementioned plug and the aforementioned "equipment".
 
  #19  
Old 04-26-16, 07:24 PM
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You need two ground rods at the building, I'll call the rods "F".

B needs to be wired all the way to the 100 amp disconnect on the pole using at least #8 copper equipment grouinding conductor.
The left ground is connected to B and not C. Use #6 copper as grounding electrode conductor.
Connect B to F (with #6 copper grounding electrode conductor).
Connect E to F (with #6 copper GEC).
C goes to the respective (left) panel neutral bus only.
D goes to the respective (right) panel neutral bus only.
Connect A to B (with #6 copper bonding jumper). Should this wire first reach one of the grounding electrode conductors it may be tied there instead of paralleling the latter all the way to B.

Your building may be grandfathered with B (EGC) and C (neutral) being one and the same (at least #6 copper). Then anything that should be connected to either B or C is then connected to it (B/C).
 

Last edited by AllanJ; 04-26-16 at 07:45 PM.
  #20  
Old 04-27-16, 08:51 AM
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Correction: The left ground is bonded to B and not C, the actual connection made inside the pole disconnect panel. No separate grounding electrode conductor runs across or under the lawn or walkway over to the building.

Since you have a disconnect box on the pole outside, the "main panel neutral bus" is out there, not in your primary building panel. "Things" in or on the building that need to be "grounded" are connected to the building grounding electrode system that includes ground bus bars in building panels but not the neutral bus bars.
 

Last edited by AllanJ; 04-27-16 at 09:14 AM.
  #21  
Old 04-27-16, 11:01 AM
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Thanks for all the responses!

A picture is truly worth a 1000 words!

Walter

I pray that this implements all changes/updates to provide safety to people inside and out. The 2 grounding rods that have been added will be more than 8' apart.
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Last edited by wpreuninger; 04-27-16 at 12:20 PM.
  #22  
Old 04-27-16, 04:30 PM
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New Diagram, New question regarding AFCI/GFCI

There were just a couple of mistakes in my most recent diagram, I think this one is right.

Would it just be as easy as running a dedicated ground from the pole grounding rod?

The 2 ground rods at the building DO NOT need to be connected, otherwise there could be a fault and it could go back to both of the 2 source neutrals.

My thought experiment of saying that one of the hot's touches the metal skin of the building show that the fault current:

A) On Utility panel would be conducted from ground, onto neutral and back to the source.

B) On Generator panel would be conducted from ground, back to the source, which is bonded internally to the generator neutral.

Now, A new question: Both panels are Homeline's with Plug On Neutral. Will there be any problems with this wiring layout and using Dual Function CAFCI/GFCI?
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Last edited by wpreuninger; 04-27-16 at 05:51 PM.
  #23  
Old 04-27-16, 06:28 PM
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Im not an electrician as stated and posted the codes regarding this.. It just looks wrong ..I am not sure your getting the best advice here..

So you have ground rods for the gen when code states its not needed?

Seems like esentially what your doing on the gen side you will have two bonds and thats not allowed AFAIK... Unless I am missing something in your drawing...

Plus I cant see your drawing and its notes as I cant zoom in...

Remember the gen is on two wheels and two rubber stops.. Its an island if you think of it that way...
 

Last edited by lawrosa; 04-27-16 at 08:31 PM.
  #24  
Old 04-27-16, 08:05 PM
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There should be no neutral to ground bond inside the right panel. (Undo the green bonding screw if any in the neutral bus bar.) This is just right for unplugging the SOOW cable from the generator and plugging it into a house receptacle powered by the left panel. You said that there is a neutral to ground bond in the generator and that can stay in place.

To be correct and up to date you need a 4 wire cable or conduit (or 3 wires in a continuous metal conduit) i.e.dedicated ground accompanying the conductors from the pole to the left panel. Then have no neutral to ground bond inside the left panel.

Should a fault occur between a hot line and the building skin then the bonding jumpers, grounding electrode conductors and equipment grounding conductors provide a path for the fault current to return to the source without going through the dirt (ground, earth, soil) which latter path would reduce the fault current to be unable to trip a breaker but still be enough to electrocute someone.

All ground rods about the building being and used for anything including TV antennas and phone equipment need to be bonded together. If a fault occurred with a hot line from the utility power, then no significant current will go the other way to the source end of the other neutral (at the generator) so as to cause problems, and vice versa, and whatever minute current that went the wrong way would also stop when the breaker tripped.
 

Last edited by AllanJ; 04-27-16 at 08:49 PM.
  #25  
Old 04-28-16, 10:46 AM
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I think there has been a misunderstanding. The left panel is only for Utility Power. The right Panel is for Generator Power, only. There is a NEMA L14-30 Plug, connected to the SOOW cable, and the SOOW is hardwired into the right panel. The conductors from the pole are hardwired to the left panel. Power to the panels, not switched. What is switched are the circuits that are essential. This switch occurs manually and only from UR1 to GR1, and back. The generator is always connected to the SOOW cable by the L14-30 Plug. The generator only runs when there is a utility power failure.

Nothing from outside is plugged inside, or vice versa.

For my sanity, I will just run a large grounding conductor (#4) from the grounding rod on the left pole, remove the panel bonding screw in the left panel, and connect the grounds together, also with #4

Why is NEC 250 so confusing?

Thanks,

Walter
 
  #26  
Old 04-28-16, 04:48 PM
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Whether or not you have a generator, whether or not you have a fat ground wire (grounding electrode conductor) running by itself between the ground rod at the pole and the left panel, if your building is not grandfathered to have just a 3 conductor feed from the pole, then you need separate ground and neutral in the cable or plastic conduit between the pole and the left panel, or 3 conductors in a metal conduit between the latter two locations.

The requirement for separate neutral and ground between the pole disconnect (if any) and the first building panel goes back quite a many years although I don't know exactly how many.

Usually, if an upstream master disconnect (the pole disconnect in your case) was added where none was before, the feed continuing downstream must be upgraded to 4 conductors (or 3 in a metal conduit).

Without a pole disconnect, you can have 3 conductor service cable between the pole and the first building panel (left panel in your picture) which would then be the panel with first whole house disconnect and with the neutral-ground bond.
 
  #27  
Old 04-28-16, 07:37 PM
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Thanks! I understand and agree. I am running 4 conductor SER cable. Makes life simple, puts me in code even though I don't have to do code, yet.
 
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