Strathead
Senior Member
- Location
- Ocala, Florida, USA
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- Electrician/Estimator/Project Manager/Superintendent
It is just that I could not find one illustration by Mike Holt shows it done this way.
Service bonding question
- Thread starter Strathead
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It is just that I could not find one illustration by Mike Holt shows it done this way.
mwm1752
Senior Member
- Location
- Aspen, Colo
But that is the thing is that there are definitely legal service bonds that create parallel paths. See the attached illustration by Mike Holt. It clearly shows bonding in the gutter, meter and disconnect while it also shows metal conduits connecting everything. That is part of the reason I asked this question.
So, If the picture represents the grounded conductor is bonded to the meter and disconnect frame it would appear the frames are of the same potential of the grounded conductor. If there is an unbalanced load on the grounded conductor it seems logical that the enclosure frames would also carry the same load as current takes all paths. I can only assume per the picture the feeder raceway is non metallic. It also shows the service raceway as metallic but I do not know if it is complete. Appears to show parallel paths -- do you have a different take on the picture?
If the grounded conductor is not bonded to either meter or disconnect enclosure no parallel paths exist
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Strathead
Senior Member
- Location
- Ocala, Florida, USA
- Occupation
- Electrician/Estimator/Project Manager/Superintendent
Then apparently you missed the note 1 attached to those conduits that states they are metal raceways.
Actually the note does not say they are metal raceways, just that if they are, they must be bonded. The caption to (1) in the graphic only says service raceways. They could be non-metallic (though I have never seen a non-metallic offset nipple of the depicted size
).Anyway, using metal raceway and/or fittings is generally accepted as compliant. Yet if one takes 250.6 quite literally, you would have to use non-metallic raceway or, at the very least, one or more non-metallic fitting to provide isolation.
Also note (2) points to the meter base as a service enclosure...
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Strathead
Senior Member
- Location
- Ocala, Florida, USA
- Occupation
- Electrician/Estimator/Project Manager/Superintendent
Actually the note does not say they are metal raceways, just that if they are, they must be bonded. The caption to (1) in the graphic only says service raceways. They could be non-metallic (though I have never seen a non-metallic offset nipple of the depicted size
Anyway, using metal raceway and/or fittings is generally accepted as compliant. Yet if one takes 250.6 quite literally, you would have to use non-metallic raceway or, at the very least, one or more non-metallic fitting to provide isolation.
Also note (2) points to the meter base as a service enclosure...
I stand corrected on that, but there is another illustration by MH that shows that threaded hubs shall be considered bonded, and that picture shows offset nipples. I can't recall ever seeing PVC offset nipple that is threaded either.
I am not contending anything you are saying. In fact that is why I was mentioning the parallel paths in my original post. And it is the exact situation of redundant paths that made me question the whole. I was reasonably secure before I started this thread and your answers merely reinforce my conviction. Thank you.
mwm1752
Senior Member
- Location
- Aspen, Colo
Apparenty you did not read carefully I was referring to the feeder conduits leaving the disconnects. I did note the service raceway was metallic
mwm1752
Senior Member
- Location
- Aspen, Colo
The example is only describing bonding of service equipment -- there is no positive proof where the grounded conductor is bonded to the enclosures. both the gutter & meter connection could be insulated from the metal enclosures with the bonding point to enclosure in the disconnect. That works well no parallel path
Strathead
Senior Member
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- Ocala, Florida, USA
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- Electrician/Estimator/Project Manager/Superintendent
Now I am thoroughly confused I do see where you said feeder, but I skipped over it because everything were talking about was up to the service disconnect and I think of service conductors as a "feeder" even though it technically is not, but... The feeder conduit has to be metal since it has no ground in it, or the illustration is not accurate in that part because the illustration is regarding the items before. As Smart pointed out, I was wrong about the service raceways too. That note actually doesn't say they are metal. I needed to read it more closely.
Strathead
Senior Member
- Location
- Ocala, Florida, USA
- Occupation
- Electrician/Estimator/Project Manager/Superintendent
But again per 250.24 (B) the grounded conductor must be bonded to the service disconnect enclosure by the "MAIN BONDING JUMPER period, so that is all the proof needed that it is bonded in the service disconnect.
mwm1752
Senior Member
- Location
- Aspen, Colo
As per my last statement which would comply with no parallel path due to the grounded conductor terminals in the meter & gutter being insulated from thier respective housing enclosures -- I get the misinterpretation with my explaination SS
The terminal and internal busing for the grounded conductor in a meter base is typically bonded to the enclosure. Emphasis on typically, as some can be isolated.
- Occupation
- Licensed Electrician
Hey Strathead, just so you don't feel like you are going crazy, anybody that cares enough to notice the fact that there are code mandated parallel paths at the service has wrestled with the notion.
The only answer is one that I remember from this site in a thread on the same topic when I joined- it went something like..."everybody knows electrons are different at the service."
The only answer is one that I remember from this site in a thread on the same topic when I joined- it went something like..."everybody knows electrons are different at the service."
meternerd
Senior Member
- Location
- Athol, ID
- Occupation
- retired water & electric utility electrician, meter/relay tech
Probably as many POCO rules as there are POCO's....here's how we state it: "Customer wiring (this includes the GEC conductor) shall not pass through or terminate in any sealed utility compartment." That means that any bonding of the neutral and grounding electrode must take place within the service disconnect enclosure. The sealed section is considered a separate enclosure, even though most are in one common meter enclosure. Usually separated by a non-removable barrier. It has caused us many a headache when the UFER stubs up though the slab inside the utility sealable "pull section". We usually allow the UFER wires to pass through our section and then terminate in the "customer" section, but we have the option of making the customer reroute the wire (jackhammer up the slab and reroute it) if the UFER interferes with our ability to pull in service conductors. Much better to ask for an inspection by the utility before the concrete work is done. Unfortunately for us, the manufacturers seem to always supply a ground bus in the pull section and stick on a label saying "Grounding Electrode Connection" next to a nice fat lug! Grrrr....... We don't want customers cutting our seals to verify GEC connections.
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Strathead
Senior Member
- Location
- Ocala, Florida, USA
- Occupation
- Electrician/Estimator/Project Manager/Superintendent
Thanks Action Dave! Compared to some of the guys here, I am a code amateur, but to the people I work with they think I am a guru. Partly because of this sire and my willingness to read and research. this issue is one of the better examples of the difficulties of the code. I an effort to present minimum requirements without tying the designer's hands, the code at times like this has small parts of the requirements spread across codes, and if you don't know what you are looking for, then a section you didn't even know about alters the outcome. I had found what I thought were the answers, but needed to make sure there wasn't another section that blew it out of the water.
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