Electrical Wizards, Another Panel/subpanel question

[Steve Barker]

Ok, i understand the whole panel/subpanel setup. And isolating the neutral from the ground in the sub etc etc. Here's the question: We've recently purchased a house (next door) and it has the typical farm setup, (meter on the pole with a disconnect, and three wires to the house). The difference with this one is that there is a second panel that was added in about 1960, when they added on to the house, which i assumed at first was just a sub off the main panel. I just noticed today that the second panel is ALSO tied into the feeders just outside the house and so it in effect is a second main panel. Are there any issues with it being this way as long as each panel has it's own pair of proper ground rods? Should the two be bonded together either at the ground rods OR between the two panels?

thanks!

[The Post Quartermaster]

I don't know the answer to your question. I'm not even sure I understand the question. But I know this. In my area, if you have a hookup like that running off of just one meter, you gonna pay. If I understand the hookup correctly, what is happening is that they were stealing power by getting an additional level of service at the reduced rate charged after a certain level of usage. People around here have actually gone to jail for that.

[Wayne Whitney]

Three wires to the house is acceptable unless (1) there is some other metallic path between the house and the pole (e.g. a phone line) or (2) you are working on the feeder and are subject to the 2008 or later NEC (existing feeders are OK). In either of those cases, you need a 4 wire feeder with an explicit EGC, and then at the house the grounds and neutrals are kept separate (with the grounding electrodes connected to the ground, not the neutral).

All grounding electrodes (e.g. ground rods) at a building must be interconnected. It is fine to have a single pair of ground rods for both panels; you could run the grounding electrode conductor to one panel and then a jumper to the next panel. If you have more than two rods, you still have to interconnect all the rods.

Also, in your situation with two main panels, the feeder neutral should be connected to the grounding electrode system at each of the main panels. This is the rare case where you interconnect ground and neutral at more than one location in a building.

Cheers, Wayne

[gfretwell]

The code says disconnects for the building should be "grouped" and you can't have 2 sets of service entrance conductors. It sounds like you have 2 disconnects in one building that are separated. I can't think of any way to fix this that is easy and 2008 code legal. I would not stay awake nights worrying about it if it is otherwise compliant.

[rlz]

Bare with me as I'm not a electrician, but why would grounding rods needs to be interconnected on the two mains panels in one building? What's the difference between one building with two main and two house next too each other with two meters that attach to the same pole wires? Just curious about the logic.

Robin

[Tony]

What??????????? I have 2 main panels run off of one main with a meter on the pole with the transformer. One to the house and one to the garage. The power company told me that is the best way to do it so I don't have to have 2 meters.

[ROANIN]

Wish they would do that for me, they made me get two meters and I have to pay commercial rates for the damned garage.

R

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[gfretwell]

Is the garage a separate structure? That is the difference. I got the impression the OP was talking about two service drops to one building.

[gfretwell]

The logic is you want one ground reference. Dirt is not really a reference in spite of the fact that we call it ground. By bonding all the electrodes together, you create a single reference point.

[Pete C.]

You missed that the meter and main disconnect for the entire residence are located on the pole, not at the house. It's also not two sets of service entrance conductors, since those end at the disconnect at the pole, after that it's feeders to the two panels.

[gfretwell]

That just moves you from 230.70 to 225.33. They still have to be grouped in one location.

[Steve Barker]

yes, two panels in the same house. the garage is detached and is fed off the pole. typical ag setup. One meter.

[RBM]

I'm not sure that I'm getting a clear picture of this setup from the OP. I see it as Wayne Whitney describes: The drop comes to the pole, down the pole into a meter, out of the meter into "the service disconnect", out of the service disconnect back up the pole, then across to house via one set of triplex. At the house the triplex is tapped into twice and feeding two separate panels.

[John Grabowski]

I think in this case the disconnect at the meter on the pole serves as the main panel and therefore the bonding of the neutral and ground should take place in there as well as your ground rod connection. So you should have four wires to each subpanel or metal conduit could serve as the grounding conductor with three wires. At the time these were installed three wires were permissible with the installation of a ground rod at each building. One shared ground rod was all that was needed at the time for both buildings.

I think that the rated life for a copper clad ground rod is 40 years. Other materials except stainless steel is less. You should probably install new rods for optimum lightning protection. Install two rods at least 16' apart and have one common grounding electrode conductor with one end going to one panel and the other end going to the other panel. Also install at least one new rod at the meter pole.

Is there a main breaker in each panel? Are the conductor sizes the same for each panel?

[Steve Barker]

exactly right

[Steve Barker]

yes, and yes. at this time, everything involved is 4ga. And it's all the same building. Actually, the panels are only about 8 feet apart, but in different rooms.

[The Post Quartermaster]

Nothing wrong with that if the power company okays it. But, as I said, I'm not sure I understand the hookup as it was described. But it sounded to me like it would be the same as if a neighbor made a deal to run their power off your meter and then split the lower cost. All I'm saying is that method is really, really frowned upon around here.

[Wayne Whitney]

gfretwell is exactly right about the need for the disconnects to be grouped, I missed that. Whoever installed the second panel installed a violation which should be fixed. So the second panel should be converted to a subpanel of the first main panel, which would require a

4-wire feeder from the first main panel. Hopefully it wouldn't be too hard to do since it is only 8 feet away.

Cheers, Wayne

[gfretwell]

Bear in mind, I also said I would not lose any sleep over the way it is done now. This is a technical violation but I don't see a huge safety issue since the service disconnect is on the pole. The fire department would pull the meter anyway and the homeowner knows what he has.

[RBM]

Those disconnects on the house are not service disconnects. The only service disconnect is on the Pole. At least by current code it should be done as John Grabowski describes. The ground rods should be installed at the pole and attached to the service disconnect. Four wires should be run from the disconnect to the sub panels at the house.