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Joined: May 2004
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It's always a good idea to talk with the AHJ.

Dave

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Joined: May 2003
Posts: 2,876
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e57 Offline
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Like I was saying earlier, I like to hit the meter section first, and lugs from there to each main, bond on the way. This way, the grounding won't have to be messed with if there ever needs to be a panel change. The meter section is as perminant as it can be, sized at 400/320A, panels get changed.... Who knows you might be the guy doing the changing.

Any way for examples sake, I have a portion of the handbook on my web-space.
http://www.markhellerelectric.com/25066.pdf


Mark Heller
"Well - I oughta....." -Jackie Gleason
Joined: Feb 2003
Posts: 687
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E57, Thanks. A piture is worth 1,000 words.

Short circuit,

Some larger homes around here have 2 200 amp panels. Each one has a seperate set of 3/0 feeding it from 1 meter base. They would not be paralell because they go to a different 200 amp panel.

Ok, I see I was using the wrong column for conductor area above. Let me try again.

2 3/0=167,800 x 2 = 335,600 circulal mils
335,600 is closest to 350 Kmil
250-66 says 350 Kmil CU = #2 CU ground

Did I get it right?

Tom

Joined: Jun 2004
Posts: 613
S
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Tom...that is the formula that I use [Linked Image]

What do you feed the meter base with...wire and pipe?

shortcircuit

Joined: Mar 2001
Posts: 2,056
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shortcircuit,
I'm not sure why you disagree with my method.
It is the same as you described in your initial response, ecxcept that the 2nd panel is also 200-amp. Therefore, the tap is #4 copper just like the GEC.

e57,
For some reason, our local PoCo won't permit GEC connections in the meter socket.

Joined: Jun 2004
Posts: 613
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Redsy...what you are telling me then is, that you run a #4 copper GEC for a 400 amp service?

shortcircuit

Joined: May 2003
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e57 Offline
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Redsy, here a picture for you... http://www.markhellerelectric.com/25024.pdf

Many linemen see grounds as a hazard, it seems. They seem to think that if the ground comes loose it will fall on the live busses of the meter, and KaBoom. (It could happen in a main the same way) Some PoCo's don't see the meter as "accessable" because they lock it, ours are just a wire, or lollipop seal.

The way I see it, if there is a bonding or ground failure in a set up where the GEC is in one panel, the other panel and the meter base is lost. Another reason I like "all-in-ones".

Anyway, what shortcircuit's getting at is, with a #4 GEC you're limited to 3/0 SEC's making it a 225A service if it were a single family dwelling. For a 320A continous, youd need 350MCM SEC's, with a #2 GEC. And another size up for 400A even.


Mark Heller
"Well - I oughta....." -Jackie Gleason
Joined: Feb 2003
Posts: 687
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Short Circuit,

We use RMC with bonding bushings between the panel(s) and meter. We run the ground rod wire to the meter.

Tom

Joined: Jun 2004
Posts: 613
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RMC [Linked Image] Tom...

1)What size service entrance conductors do you feed the 320 meter can with on the line side?

2)What size and type conduit are SEC installed in on the line side of the 320 meter can?

3)What size bonding jumper do you install from the RMC nipples on the line side of the service disconnecting means?

shortcircuit

Joined: Mar 2001
Posts: 2,056
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shorty,
I have only done a couple of these and now that I think about it, they had wellwater, so the only GE was (2) rods, which, although only #6 is required I ran #4.
However, in my area, I have seen several installations like the one described, and never saw more than a # 4 GEC.

BTW,
I'm not sure that this is a "true" 400-amp service, although Note 1 to Table 250.66 would still seem to require an upsized GEC .

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