Residential Grounding and bonding

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Johnhall30

Johnhall30

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Location
New Orleans, LA
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Engineer
I see residential installations in my area like this all the time. Is this code compliant?

The meter can has a neutral to ground bond, which is also bonded to the meter enclosure, with a grounding electrode that goes to the ground rod, and the bonding screw installed in the main panel.

Wont this create three parallel paths from the panel to the meter enclosure? 1) The neutral 2) the bare ground and 3) the enclosure and conduit between the meter and panel

1649782487745.png
 
Parallel ground paths with service equipment (meters, service panels, etc.) are a common acceptable issue.
The picture you show is a somewhat common installation.
 
augie47 said:
Parallel ground paths with service equipment (meters, service panels, etc.) are a common acceptable issue.
The picture you show is a somewhat common installation.
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I agree. But I would point out that the bonding bushing at the bottom of the meter can is not required in this install.
 
texie said:
I agree. But I would point out that the bonding bushing at the bottom of the meter can is not required in this install.
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I agree and in doing so you created a violation of further causing objectionable current.
 
Johnhall30 said:
I see residential installations in my area like this all the time. Is this code compliant?

The meter can has a neutral to ground bond, which is also bonded to the meter enclosure, with a grounding electrode that goes to the ground rod, and the bonding screw installed in the main panel.

Wont this create three parallel paths from the panel to the meter enclosure? 1) The neutral 2) the bare ground and 3) the enclosure and conduit between the meter and panel

View attachment 2560210
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What is the elevation of the meter? It looks like a ladder is necessary to reach it?
 
Yes the meter looks too high. The local utility wants the meters at 6'5 AGF max. I just used this picture as an example for grounding and bonding discussion. It is not my work
 
texie said:
I agree. But I would point out that the bonding bushing at the bottom of the meter can is not required in this install.
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What about 250.92(B) for the offset nipple? Seems like the locknut/nipple flange is not one of the methods listed there. And if the offset nipple has to be at a particular rotational position to get the desired offset, it may not be "wrenchtight" in the hub below.

Looks like the last 6" or so of the GEC is serving dual purpose here as an equipment bonding jumper for the offset nipple.

Cheers, Wayne
 
wwhitney said:
What about 250.92(B) for the offset nipple? Seems like the locknut/nipple flange is not one of the methods listed there. And if the offset nipple has to be at a particular rotational position to get the desired offset, it may not be "wrenchtight" in the hub below.
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It could be that it's not wrench tight but it's all moot anyway becuase its a violation to have an offset nipple with straight threads in the hub.
 
My opinions, in no particular order:

The hub is adequate for bonding the nipple, but I'm not sure if offset nipples are suitable for service conductors.

The meter and main panel enclosures are "part" of the neutral, and is expected, but the parallel bare wire is not.

I don't think any of the bare wire should be in the meter, or at all. A service nipple can be bonded at only one end.
 
Johnhall30 said:
The GEC is touching the enclosure in 4-5 different spots so the objectional current would already be on the enclosure
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That's true but you're still required to limit any unnecessary connections that would cause objectionable current.

250.6 Objectionable Current.
(B) Alterations to Stop Objectionable Current. If the use of multiple grounding connections results in objectionable current and the requirements of 250.4(A)(5) or (B)(4) are met, one or more of the following alterations shall be permitted:
(1) Discontinue one or more but not all of such grounding connections.
(2) Change the locations of the grounding connections.
(3) Interrupt the continuity of the conductor or conductive path causing the objectionable current.
(4) Take other suitable remedial and approved action.
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To add: The panel's hub should be able to be positioned so no offset is needed, just a close or short nipple.
 
LarryFine said:
My opinions, in no particular order:

The hub is adequate for bonding the nipple, but I'm not sure if offset nipples are suitable for service conductors.

The meter and main panel enclosures are "part" of the neutral, and is expected, but the parallel bare wire is not.

I don't think any of the bare wire should be in the meter, or at all. A service nipple can be bonded at only one end.
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Many POCOs require the GEC to be landed in the meter. It would be redundant to land it in both the panel and meter base. But in the OP's pic it appears they just ran the GEC through the panel without landing it there, then landed it in the meter base.

I like putting the GEC in the meter base as it avoids having to use jumpers on multiple panels or disconnects.
 
The POCO up here does not want a ground in the meter base, we bond it, but no ground wire in the can


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Johnhall30 said:
Yes the meter looks too high. The local utility wants the meters at 6'5 AGF max. I just used this picture as an example for grounding and bonding discussion. It is not my work
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We have no grade reference in the photo. You are assuming the loadcenter is higher above grade than it possibly is?
 
LarryFine said:
My opinions, in no particular order:

The hub is adequate for bonding the nipple, but I'm not sure if offset nipples are suitable for service conductors.

The meter and main panel enclosures are "part" of the neutral, and is expected, but the parallel bare wire is not.

I don't think any of the bare wire should be in the meter, or at all. A service nipple can be bonded at only one end.
Click to expand...
In theory I agree, per listing I'm pretty certain those hubs are intended for tapered threads like you would have on threaded RMC/IMC. Hardly any "fittings" out there that don't have straight thread, and the reason why many fittings get tight before they are threaded very far into such a hub.

That said, you don't see much enforcement of this.

I have no idea if typical offset nipples are suitable for use in service applications, but seen many used in service applications. I don't see them being that different in conductivity abilities as same trade size and material of actual raceway though. (2 inch cast aluminum offset likely has similar enough properties as short nipple of 2 inch aluminum RMC)

Add: I guess what I called cast aluminum is typically cast zinc and not aluminum.
 
I've done the entire photo other than mine isn't near as pretty. A city inspector called me out for parallel neutral but never made me change it. I eventually changed my ways.

I think a major POCO meter height is 5'6" to center max. That and hubs dripping water onto main connections changed us to side by side installs for the most part.
 
ptonsparky said:
I've done the entire photo other than mine isn't near as pretty. A city inspector called me out for parallel neutral but never made me change it. I eventually changed my ways.

I think a major POCO meter height is 5'6" to center max. That and hubs dripping water onto main connections changed us to side by side installs for the most part.
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I've seen the results of that myself many times and typically try to avoid doing it as well.

Had one last summer that was probably ~30 year or better installation. You probably know NPPD hasn't and still doesn't necessarily put weatherheads on their end of underground laterals that originate at top of a pole. This was one that likely was that way when initially installed, but a second structure to be supplied was added at some time and they just moved the meter to the pole, with a meter/main assembly, but never put a weatherhead on the top of the conduit. Surprised that main breaker lasted as long as it did, especially with aluminum wire in it. We replaced the breaker and had a weatherhead put on the conduit.
 
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