Grounding for outbuildings fed without EGC

N

nymtns

Member
Location
Well north of NYC, well south of Canada
Occupation
Engineer
I ran into an odd situation at a property a friend inherited. There are 3 structures on the lot, each about 100' apart, and a swimming pool.

The utility service comes in at one corner of the lot and originally ran underground 100' from the last pole to the main house, which had a 200A disconnect with a neutral bonding jumper installed.

From the main panel in that house, there was a feeder to a shed - with no EGC - the outbuilding had two rods and, again (no green wire in the feeder) the bonding jumper installed in its subpanel, which I understand was good per code at that time. This bonding jumper has been removed by others (see below), which I question, since there is no EGC in the feeder cable.

From there to the swimming pool runs another feeder without ground, and at the pool, there's a 6 space panel for the pool pump and heater, again with a rod, a bonding jumper to neutral (this one still connected), and what appears to be proper bonding of the pool equipment, rebar in the pool deck, and fence.

Some time in the 1990s, two changes were made.

1) A detached garage was constructed on the corner of the lot where the service enters, and the SE moved there. Two new rods were driven and neutral and ground bonded in the new service entrance panel. The original buried service entrance cable (again: no ground wire!) was reused to feed the main house. The bonding jumper was removed from the original service disconnect at the main house.

2) Rodents nested in the subpanel in the outbuilding between the main house and pool, which started a small fire. The subpanel was replaced and the jumper between neutral and ground was not installed in the new subpanel.

So the situation now looks like:

SE panel at garage (with rods and jumper)-feeder without EGC->Main House (with rod and water pipe ground)->feeder without EGC->shed (with rods, no jumper)->feeder without EGC->pool (rod plus CEE, jumper).

Not on the menu: digging up all the feeders. The grounding rods are actually in decent shape except at the shed, where I'll replace them - noticing the shed subpanel was "too new" and not jumpered as I would have expected for this era of construction was what made me look at all the rest actually. What's the right, code-compliant path forward?
 
At one time three wire to the buildings were legal along with GES at each. Even feeders from one building to another as long as there was no common metallic path between them. Neutrals were bonded at each SE.

I don't believe you can make it all legal now without starting over. Too many changes in the years that would now require 4-wire feeders along with GES at each location.
Add the pool and now it's possibly deadly.

IMO, you need to change the menu or let the customer go to another restaurant.
 
My impression is that it was all legal when it was done, except the removal of the bonding in the two modifications made in the 1990s, which I think was probably a mistake on the part of the electrician who did the work at the time. I actually don't see a safety issue at the pool because, despite what was done wrong in between the garage and the shed (breaking the bond on both those 3-wire feeders) the pool panel is bonded. Are you thinking of a safety issue I'm missing?

I'm looking at this as a favor to my friend. I'm not going to do the work nor is my name going on any filings. But it also seems clear that the two electricians in his town, both of whom have recently worked on this property (and one of whom probably messed this up 20-25 years ago) are also unsure what to do and want guidance. In the abstract, I wonder if just putting it back how it originally was (restoring the bond at the original service disconnect at the house, and the subpanel in the shed) would be safest, short of digging up all the feeders - and if so, whether they should just ask the AHJ for permission to do so.
 
Actually, as I think about this more - there are metallic water lines between house and pool, and house and garage, and the bonding to the pool equipment means that if the bond at the house were restored, there would be a second path for neutral fault current paralleling at least two of those 3-wire feeders. Which leaves me now thinking this was not legal when originally built, with those jumpers in place that were subsequently removed.

The other possibility, which I hadn't considered, would be replacement of the questionable ground rods at the shed without restoring the bond at that panel, and disconnecting the jumper at the pool panel. Thinking about it from first principles, this leaves all the structures with a safety ground, but the neutral is referenced only to the ground at the service entrance. I wonder about the impact on lightning protection, but aside from that, this seems better. Would it be legal? The mess of language around the exceptions in 250.32 makes my head spin.
 
Back in the day when they didn't run a grounding conductor to all the outbuildings on the property there was a N-G bond at every building's first disconnect.

Typically at a farm either the house or a pole in the yard would have the poco service. From there they would run 3 overhead conductors 2 hots 1 N to each building either radially from the pole, or in a daisy chain. The service to each building was treated just like an incoming service from the POCO. Each building would have it's own ground rod and N-G bond. If the bond was missing chances are the overload protection on that building's circuits would not open if there was some kind of fault to ground.

That was typical family farm power distribution back in the day. Now things are different and you can't install like that. It was more or less a 20's to 60's way of doing things.

That is a historical perspective on it, nothing to do with what is safe or what is code compliant
 
The EGC provides a low-impedance path for fault current to earth, reducing the likelihood of that current finding a path through a human. There is an EGC within each of these structures; the problem is that there's no EGC between them, and additionally (as I've realized while discussing this here) that even if the pre-2008 rule were followed and the bond reestablished at each structure, a different safety issue would arise, namely current on the water pipe in case of an open neutral.

Looking at the existing conditions in the main house - where there's a 3 wire feeder going "both ways" from the panel, no bond between ground and neutral, but a good pair of grounding electrodes (rod, pipe) taking the EGC within the structure to earth potential - it looks strictly safer than if the earth grounds were not there. Is that wrong?
 
Joethemechanic said:
That was typical family farm power distribution back in the day. Now things are different and you can't install like that. It was more or less a 20's to 60's way of doing things.

That is a historical perspective on it, nothing to do with what is safe or what is code compliant
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I wondered about that. This is about 50 miles south of where I live, downhill out of the mountains into farm country, and I believe the 1980s "main house" on this property was constructed on the existing footprint of some kind of farm structure that burned. The feeder to the shed at least might predate the 1980s (though the wire within each structure looks much newer than the 1960s, there are quite likely buried splices I don't know about).

I'm getting to the point of just telling my friend I have no suggestions other than to dig up and replace the feeders. If that's the only way that's safe and the only way that's currently to code, so be it.
 
What was considered safe then was not what we call safe now. In 2125 they will look and what we did and we will look like this to them.

550 3.png
 
nymtns said:
The EGC provides a low-impedance path for fault current to earth, reducing the likelihood of that current finding a path through a human. There is an EGC within each of these structures; the problem is that there's no EGC between them, and additionally (as I've realized while discussing this here) that even if the pre-2008 rule were followed and the bond reestablished at each structure, a different safety issue would arise, namely current on the water pipe in case of an open neutral.

Looking at the existing conditions in the main house - where there's a 3 wire feeder going "both ways" from the panel, no bond between ground and neutral, but a good pair of grounding electrodes (rod, pipe) taking the EGC within the structure to earth potential - it looks strictly safer than if the earth grounds were not there. Is that wrong?
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Yes, that is wrong.
 
ptonsparky said:
Yes, that is wrong.
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I don't mean to be dense nor to make you repeat yourself, but why? Surely it's no less safe, and - whether ideal or not - I have trouble seeing why it would not be more safe to have a redundant path from where there's more charge to where there's less, even if that is not at the exact same potential as the bond between neutral and ground 100' away at the service entrance.

Noting at this point my interest is pretty much academic only, so, if educating me doesn't seem like the best use of your time, I totally get that.
 
ptonsparky said:
At one time three wire to the buildings were legal along with GES at each. Even feeders from one building to another as long as there was no common metallic path between them. Neutrals were bonded at each SE.

I don't believe you can make it all legal now without starting over. Too many changes in the years that would now require 4-wire feeders along with GES at each location.
Add the pool and now it's possibly deadly.

IMO, you need to change the menu or let the customer go to another restaurant.
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^^^^^^^^^^That!
With a pool involved all bets are off.
 
nymtns said:
Surely it's no less safe
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If for not other reason (which have and will be mentioned here) it is less safe simply because there is a false sense that it is safer when it's not. If the people who are in, or around, this system believe it is potentially dangerous, they will be more cautious. If the believe it's "safer" then they may be less cautious and therefore at a higher risk.

And don't call me Shirley.

;)
 
Kinda of a hack but I'd say take a close look at the 120V loads and see if by chance they can be converted to 240V, many can be these days, you'd need a 2-pole breaker and switch for 240V LED yard lighting.
You could tape the feeder neutrals green and convert it to an ECG and remove all the 120V loads.
You'd convert all the neutral bars to ground bars.
Put a sticker on the panels '240V loads only' or something to that effect.
Make sure each panel is bonded to the equipment ground bar and each structure has 2 ground rods.
The catch is I don't think you land the white wire from a GFCI breaker for the pool on a equipment ground bar and not violate the listing, but I have never looked into it it may be allowed.
 
tortuga said:
The catch is I don't think you land the white wire from a GFCI breaker for the pool on a equipment ground bar and not violate the listing, but I have never looked into it it may be allowed.
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You could install a transformer and have a SDS for the 120v loads,,,,,,,,,,,,,,,,,,,


 
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