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Sub Question


CHI2
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At a 1947 home today I came across 2 200 amp panels. One had a 200 main breaker and a 100 amp breaker labled Sub panel. The majority of the breakers for the home were in the sub, however the sub had a main breaker of 200 amps. The sub was also bonded to the panel, however the jumper between the neutral and ground bars was removed. Any suggestions?

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Originally posted by CHI2

At a 1947 home today I came across 2 200 amp panels. One had a 200 main breaker and a 100 amp breaker labled Sub panel. The majority of the breakers for the home were in the sub, however the sub had a main breaker of 200 amps. The sub was also bonded to the panel, however the jumper between the neutral and ground bars was removed. Any suggestions?

If I understand this properly, you've got a 200-amp service panel. In this panel, there's a 100-amp breaker that feeds a second panel. The second panel has a 200-amp main breaker.

If I've described this much properly, it's fine so far.

Next, you say that the sub panel is bonded to the main panel. That's fine.

Last, you say that, in the sub panel, the jumper between the grounding terminal bar and the neutral terminal bar has been removed. That sounds fine also.

Did the sub panel feeder contain four wires? If so, then it sounds ok to me.

- Jim Katen, Oregon

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Sounds like you saw a 200 amp main panel with sub panel. To say you had 2 200 amp panels would be off the mark. The 200 amp breaker in the sub is irrelevant since power is supplied and limited by the 100 amp breaker in the main panel. The service would be 200 amps.

As for the bonding - you lost me.

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Yeah, that sounds right.

One thing Jim, the sub is bonded at the ground bar to the sub panel enclosure. That's throwing me. I thought that strap needed to go.

And thanks for the correction Eric. I knew the moment I typed 2-200 amps someone would catch me!

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Hi,

I don't really see a problem with him reporting that it was 2-200 amp panels, as long as each panel is rated for 200 amps. He could have one 200 amp panel and one 100 sub-panel and it wouldn't change the fact that he's got a 200 amp service. I think it can help to know what the sub-panel enclosure is rated for.

Rob, the ground bus is supposed to be bonded to the enclosure in a sub-panel. It's the neutral that's supposed to be isolated from the EGC's and the enclosure.

So, how many conductors are feeding the sub?

OT - OF!!!

M.

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Originally posted by CHI2

I've got a picture of it. Let's see if this loaded correctly.

In the picture I see four feeder wires, the grounding terminal bar bonded to the panel enclosure and the neutral bar floating. I think that much is fine.

The only thing that doesn't make sense in there is the second large, bare grounding wire. What's that doing there? Where does it go? Is this sub panel very far remote from the service panel?

It shouldn't be under the same lug as the other grounding wire. That lug is only listed to hold a single conductor.

- Jim Katen, Oregon

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The sub is about 25' from the main panel. I could not trace the second grounding wire to its location. There was a bare wire at the water heater and at the galvanized waste line.

I'm glad I brought this up. It all looked ok as far as the 100/200 situation. I just thought I'd better run it past the experts.

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Where are the two(?) bare copper ground wires going? It looks like they're exiting the enclosure through a hole drilled in a knockout(?). Are they the wires that go to the wate heater & galvanized waste line?

I'm mildly confused, and only looking for clarification.....I have no answers.

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Hi,

They look like home run bonding cables to me. I agree with Jim; they should be on the bus, not that one-conductor lug. If there isn't a hole large enough in the ground bus for them, there should be separate lugs for each. It would have made more sense to have those in the main panel, No?

OT - OF!!!

M.

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The location of the sub was the original location of the main panel. It appeared the home had overhead service and is now buried. The service now enters from below where the "new" main is installed. The new main now feeds the sub which contains the majority of breakers. It appears they didn't want to come to the rear of the home with the new entrance so they opted to install a new panel along with the sub. The home was only 1300 sq ft. with a detatched garage that had a light and one receptacle. Kind of overkill. But of course the knob and tube buried in the attic and ungrounded three pronged outlets remained.

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Originally posted by CHI2

The location of the sub was the original location of the main panel.

Well that probably answers the question about why there are two big grounding conductors. One of them is taking the place of the original grounding electrode conductor. Given the age of the home, I'll bet that it connects to a cold water pipe. When they installed the new service, they probably drove a new pair of grounding electrodes and ran a wire from them and from the water pipe to the new service panel. Oftentimes, the AHJ likes them to preserve the old grounding electrode conductor even though it isn't strictly necessary. I'll bet that's what the second bare wire in your picture is.

It appeared the home had overhead service and is now buried. The service now enters from below where the "new" main is installed. The new main now feeds the sub which contains the majority of breakers. It appears they didn't want to come to the rear of the home with the new entrance so they opted to install a new panel along with the sub.

I'm surprised that they didn't just install a 200-amp meter main. It would have been quick and easy.

The home was only 1300 sq ft. with a detatched garage that had a light and one receptacle. Kind of overkill. But of course the knob and tube buried in the attic and ungrounded three pronged outlets remained.

Well, one thing at a time. Incremental improvements are better than none at all.

From your descriptions and the picture, I think that the installation is fine. The double connection at the grounding lug is a quibble that they can get fixed the next time an electrician is present for other repairs.

- Jim Katen, Oregon

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Mike,

As for saying 2 200 amp panels - It would seem that that could easily be interrupted by the client as 400 amp service.

I think that it is important for the inspector to know what the panels are rated for but not worth communicating to the client. I've had clients notice the disconnect for the subpanel and begin adding up numbers figuring that somehow the 200 amps had been amped up to 300.

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