two buildings,2 mains, 1 generator

[twistin214]

we have two residential buildings. building #1 has 2-200 amp main discs. 1 feeder was ran(3 wire) to building #2 for majority of load.
2nd feeder suplying building #1 goes through generators transfer switch into sub panel then also feeds building #2.(again unfortunatley only 3 wire).
my head is spinning with all the diffrent comments on how to ground bond this.the inspector said it's like a new service just like mike holt said he would. i am confused and keep thinking about all this stray objectionable current flowing around the earth.i believe the gen is shipped out with a nueteral/ground bond. how many paths are we creating here? thanks for your help.
fyi-building #1 is garage and building#2 is a house

 

[hillbilly]

The first thing that I would do is draw the circuits on a piece of paper. It makes it's a lot easier to see what you're dealing with.
Is the generator going to be permanently installed, or a portable?
What kind of transfer switch?
steve

 

[twistin214]

i thought i had it last night but have lost it now. it is a permanent generac generator with automatic power that has been installed for some time .
currently the two feeders come into the house, to me one is a 200amp sub panel and the other a 100 amp sub/gen.panel.the distance was about 200' and that was there reasoning on not running the gec. they are treating it like a new service. is this compliant?

 

[George Stolz]

Twistin, do I have this right?

I didn't draw in grounding paths at all, because it's unnecessary.

Suppose the red cables entering Disconnect #1 and the transfer switch are service conductors. There will be a neutral loop between these two boxes. It can be minimized, but will be present. All the grouped service disconnects are required to be connected to the Grounding Electrode System present at the structure.

Note, if the picture is perfect (and the red groups are service conductors) then the transfer switch must be service rated.

When you get to the second building, the house, the tone changes. These conductors are outside feeders, not service conductors. An Equipment Grounding Conductor must be run with these conductors, because it doesn't comply with 250.32(B)(2). There are two neutrals, there have to be.

Two neutrals would constitute a violation of the second condition of 250.32(B)(2).

Give me corrections on the picture, and I will edit the original.

 

[twistin214]

thanks george for the drawing and help- building 1's 2nd 200 amp disco goes:disco/sub panel/transfer switch/100amp sub panel, that is 2nd feeder to house. there idea was to prep for future house and have a generator feed a little bit of garage and house.
-my issue is i had told builder,supply house,& boss that each feed needed it's own gec. the inspector said that the distance was far enough @300' that it was like a new service. re-bond. my boss agrees with this theory and both panels are currently bonded through grnd rods.
i am just understanding enough to be getting it, and not debating parallel nueterals with them. the job has been completed & i have not been able to let go. i could somehow slide my way back there if this application deems too dangerous. is the grounding and bonding electrical world always this dramatic.thanks again

 

[George Stolz]

thanks george for the drawing and help- building 1's 2nd 200 amp disco goes:disco/sub panel/transfer switch/100amp sub panel, that is 2nd feeder to house.

Okay. I'm headed to bed, I can correct this if the need arises.

My issue is i had told builder,supply house,& boss that each feed needed it's own gec.

Keep your terms straight. The conductor running from the garage to the house would be an EGC, not a GEC.

The inspector said that the distance was far enough @300' that it was like a new service. re-bond.

That's section 187 of the good ol' boy handbook: Throw the NEC out the window when it's inconvenient. If you're trying to make code-sense out of what's going on, it's not going to happen. Services are services as far as the NEC is concerned. If it's not directly connected to a utility, it's not a service. So saying, "That looks a lot like a service from my house" doesn't change the fact that it's not.

my boss agrees with this theory and both panels are currently bonded through grnd rods.

Of course he agrees; it's cheaper.

What do you mean when you say "both panels are bonded through ground rods"?

i am just understanding enough to be getting it, and not debating parallel nueterals with them. the job has been completed & i have not been able to let go. i could somehow slide my way back there if this application deems too dangerous.

Let's say disconnects 3 & 4 each have their own GEC to a common ground rod. The parallel GEC does form a parallel path for the neutrals. Now the neutrals are one parallel conductor, of uneven length (and undersized, if the GEC is #6). Will it cause a fire? Who knows.

I would not waste the breath in trying to change the EC or the Inspector. I would move.

Is the grounding and bonding electrical world always this dramatic.

I think so - it's all so misunderstood that it has to be. The other day I heard someone I believe actually knew better speaking of a grounding electrode as a ground fault current path. I suspect it was multiple thoughts funneling through one mouth at the same time, getting garbled. I hope.

 

[twistin214]

-each panel has a #4 gec out of it going to 2 common grnd rods.
-the look on faces when i say that grnd rods are not for clearing faults is un explainable. i believe the older school theory was that when in doubt, drive a grnd rod. why send it back to the source when you can go to earth here.
-since mike holt & this forum i understand more theory but in this situation maybe ignorance is bliss.

 

[George Stolz]

For what it's worth, they are right in that services are allowed to have some hijinx going on as far as bonding goes. Circular paths can be hard to avoid at times.

But just because we're allowed to do things somewhat wrong in some circumstances, is not an excuse to do as we please at any time, IMO.

 

[bill@nkapc]

If the buildings are seperated a distance of perhaps 100', no metalic connection possible,-faulty gnd path posible- treat the overhead or underground as a seperate service. Install ground rods, and main breakers in the 2 panels in the garage.

 

[George Stolz]

If the buildings are seperated a distance of perhaps 100', no metalic connection possible,-faulty gnd path posible- treat the overhead or underground as a seperate service. Install ground rods, and main breakers in the 2 panels in the garage.

Bill, could you please clarify your statement? If you treat the house's disconnects as a seperate service, then the disconnects would have to be both connected to the grounding electrodes at that house.

If they are properly connected, then it will allow neutral current from either disconnect to flow onto the neighboring feeder's neutral. It would violate 250.6 and 250.32, perhaps even more sections than that.

 

[George Stolz]

Twistin, is there a service disconnect where the red ? is? Or do I have the service side of the transfer switch wrong?

 

[twistin214]

2nd service in garage, everything else is right

service conductors to single 200amp disco box
then to non-generator sub panel,which has a 100amp break going to-
transfer switch for generator, that powers-or feeds a
sub panel in garage and has our second feeder to house for sump,ect..

-i am not sure who is in the ufo flying between the two buildings in your schematic, but i'm guessing that he or she is studying or keeping a watchful eye on paralell nueterals.

 

[George Stolz]

I updated the picture with the UFO. Does that look right?

You're filling up my garage wall with all your junk, M.

 

[twistin214]

that is it. i better get some computer skillz to be able to post a drawing like that. i read a post from 2004 about the hazard potential of someone touching both panels with a lost nueteral. is it going in the wrong direction to think about not bonding the panels(knowing that an electrician in the panel won't let a hot wire touch the side) & not bonding the 2 systems through grnd rods? just a thought & 4 wire should be ran with other metallic or not. so much easier. it also drives me crazy in older homes buying a new appliance that is prepped for a nuteral grnd bond.

 

[George Stolz]

I read a post from 2004 about the hazard potential of someone touching both panels with a lost neutral.

Touching either panel and earth would complete a circuit. Touching both panels would be unnecessary, to receive a shock under an open (or high-resistance) neutral.

Is it going in the wrong direction to think about not bonding the panels...

Without a doubt that is a bad idea.

(knowing that an electrician in the panel won't let a hot wire touch the side)

Bonding is essentially insurance against the unknown. An electrician is the last thing that will probably cause the panel to become energized. Time and chance is what we're insuring against, not qualified personnel.

(What about) not bonding the 2 systems through grnd rods?

I think having all the electrical equipment in the house bonded to the same potential is a greater concern than the parallel neutral issue.

All thing being equal, the installation is wrong. Once that is established, then we venture into the shades of gray arena. What's worse, parallel neutrals or having a chance of different potentials between the frame of the refrigerator (which is likely on Disconnect (6)) and the surface of the lamp (which could be on Disconnect (2)).

It's like saying, "I'd rather die of extreme cold than extreme heat". There are drawbacks and advantages to either fate. It's complicated.

4 wire should be ran with other metallic or not. so much easier.

It is easier to implement, and have future changes covered at the same time. But, at the same time, generally the neutral is larger than the EGC that the code would require. A larger neutral (or ground) will have less resistance, and will kick a circuit breaker better under a short circuit or ground fault.

In my opinion, 250.32(B) is very good as it is.

it also drives me crazy in older homes buying a new appliance that is prepped for a nuteral grnd bond.

I bet their thinking is, they would rather deliver an appliance that may be misinstalled with a fault clearing path than an appliance that doesn't, that could shock someone and get the appliance manufacturer sued. But that's a guess on my part.