Our REMC has always required that the grounding electrode conductor be landed in their meter base. Now they have a new operations manager and a new line superintendant. The new Ops manager wants to require a GEC connection in the main OCP as well as in the meter base. The new super, who is a 27 year lineman/serviceman doesn't think it is right to ground the neutral in 2 places. I agree and he has asked me to help find NEC references to support our position so he can propose a policy change to the board next month. If anyone can help with 2002 NEC article references it would be very appreciated. My position is the neutral should be grounded in only one place, preferably at the first means of OCP. I think doing it in the meter base is a likely violation of 250.24(A)(5). I never considered the meter base as a means of OCP.
Residential service grounding
- Thread starter amptech
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hurk27
Senior Member
- Location
- Portage, Indiana NEC: 2008
Re: Residential service grounding
When did kankakee valley start this? we have always landed in the OCPD since we do most of our work in NIPSCO's teritory it was a habbit. We were never told not to. We don't even use those meters with the bypass any more since we have to supply them they told us it was ok to use the same base that NIPSCO uses.
As for the two places of bonding look at 250.30 (A)(1) Exception No. 1
Exception No. 1: A bonding jumper at both the source and the first disconnecting means shall be permitted where doing so does not establish a parallel path for the grounded circuit conductor. Where a grounded conductor is used in this manner, it shall not be smaller than the size specified for the bonding jumper but shall not be required to be larger than the ungrounded conductor(s). For the purposes of this exception, connection through the earth shall not be considered as providing a parallel path.
When did kankakee valley start this? we have always landed in the OCPD since we do most of our work in NIPSCO's teritory it was a habbit. We were never told not to. We don't even use those meters with the bypass any more since we have to supply them they told us it was ok to use the same base that NIPSCO uses.
As for the two places of bonding look at 250.30 (A)(1) Exception No. 1
Exception No. 1: A bonding jumper at both the source and the first disconnecting means shall be permitted where doing so does not establish a parallel path for the grounded circuit conductor. Where a grounded conductor is used in this manner, it shall not be smaller than the size specified for the bonding jumper but shall not be required to be larger than the ungrounded conductor(s). For the purposes of this exception, connection through the earth shall not be considered as providing a parallel path.
Re: Residential service grounding
250.30 has nothing to do with SERVICE equipment.
250.24 has to do with services, then go to 250.28, 250.50.
My take is; The Grounded Service Entrance conductor is permitted to be grounded at any point from the Service Point to the Disconnect enclosure.
Since the meter grounded conductor is factory grounded to the metal enclosure and if a metal raceway is used between the meter enclosure and the main disconnect enclosure, there is always a parallel path.
This practice is many code cycles old and there has been proposals to prohibit this parallel path which the CMP has not accepted.
In the last 3 or 4 code cycles, this parallel path has been getting more attention though.
Even though the voltage drop on/of the metal enclosure between the meter and the main disconnect is ususally very low, the amperes actually carried by the metal raceway can be more than the current carried by the grounded conductor with-in the metal raceway when the grounded conductor is carrying considerable un-balanced current.
Example: A 200A dwelling service with the grounded conductor ( 8 feet of 2/0 Cu between the meter and the Main OCPD) carrying 30 amps of unbalanced current that is in 5' of RMC , the 2/0 copper conductor is carrying 11.99A and the 2" RMC is carrying 18.01A.
The voltage drop is 0.0093V for the 5' or so in the RMC.
The above study was with resistive loads only.
The above study shows that the RMC is almost carrying 2 times the 2/0 copper conductor current.
There must be many thousands such services in use today.
Until the electronic age, I do not beleive it caused much of a problem, but now, the non-linear loads!
gwz2
250.30 has nothing to do with SERVICE equipment.
250.24 has to do with services, then go to 250.28, 250.50.
My take is; The Grounded Service Entrance conductor is permitted to be grounded at any point from the Service Point to the Disconnect enclosure.
Since the meter grounded conductor is factory grounded to the metal enclosure and if a metal raceway is used between the meter enclosure and the main disconnect enclosure, there is always a parallel path.
This practice is many code cycles old and there has been proposals to prohibit this parallel path which the CMP has not accepted.
In the last 3 or 4 code cycles, this parallel path has been getting more attention though.
Even though the voltage drop on/of the metal enclosure between the meter and the main disconnect is ususally very low, the amperes actually carried by the metal raceway can be more than the current carried by the grounded conductor with-in the metal raceway when the grounded conductor is carrying considerable un-balanced current.
Example: A 200A dwelling service with the grounded conductor ( 8 feet of 2/0 Cu between the meter and the Main OCPD) carrying 30 amps of unbalanced current that is in 5' of RMC , the 2/0 copper conductor is carrying 11.99A and the 2" RMC is carrying 18.01A.
The voltage drop is 0.0093V for the 5' or so in the RMC.
The above study was with resistive loads only.
The above study shows that the RMC is almost carrying 2 times the 2/0 copper conductor current.
There must be many thousands such services in use today.
Until the electronic age, I do not beleive it caused much of a problem, but now, the non-linear loads!
gwz2
hurk27
Senior Member
- Location
- Portage, Indiana NEC: 2008
Re: Residential service grounding
Glen
Let me ask this question. Where does the NEC require a 4th grounding wire on a 3-wire service when there is PVC ran between the meter and the main OCPD? I have been with the understanding that this is not needed as the wires between these two points are still part of the service entrance wires and since the grounded conductor is bonded at the meter as well as the OCPD there is no requirment to run an extra EGC. I agree that the RMC/neutral paralleling is un avoidable unless we didn't bond in the main OCPD panel/disconect but when we run PVC it is. I have seen where one of these grounding conductors did get warm and melted the insulation but I dont know if it was because of a lost neutral.
Glen
Let me ask this question. Where does the NEC require a 4th grounding wire on a 3-wire service when there is PVC ran between the meter and the main OCPD? I have been with the understanding that this is not needed as the wires between these two points are still part of the service entrance wires and since the grounded conductor is bonded at the meter as well as the OCPD there is no requirment to run an extra EGC. I agree that the RMC/neutral paralleling is un avoidable unless we didn't bond in the main OCPD panel/disconect but when we run PVC it is. I have seen where one of these grounding conductors did get warm and melted the insulation but I dont know if it was because of a lost neutral.
Re: Residential service grounding
The addition of a small EGC in parallel with the Grounded Service Entrance Conductor between the Meter enclosure and the Main OCPD is a violation of 250.24,
310.4, and maybe other Sections, when in RNC.
Yet, this parallel path is permitted when a metal raceway is used.
A Catch-22 ?
gwz2
The addition of a small EGC in parallel with the Grounded Service Entrance Conductor between the Meter enclosure and the Main OCPD is a violation of 250.24,
310.4, and maybe other Sections, when in RNC.
Yet, this parallel path is permitted when a metal raceway is used.
A Catch-22 ?
gwz2
hurk27
Senior Member
- Location
- Portage, Indiana NEC: 2008
Re: Residential service grounding
Thank's Glen this is what I thought but you know around here one AHJ will make you install it another will make you take it out.
Thank's Glen this is what I thought but you know around here one AHJ will make you install it another will make you take it out.
brian john
Senior Member
- Location
- Leesburg, VA
Re: Residential service grounding
Taking this a step further (past the main). In commercial installations we see utility meter cans utilized downstream from the main service, with the neutral bonded (per design). This is a violation and does create net current issues but usally only becomes a problem (when it is noticed) when the main GFP protected switch trips.
Taking this a step further (past the main). In commercial installations we see utility meter cans utilized downstream from the main service, with the neutral bonded (per design). This is a violation and does create net current issues but usally only becomes a problem (when it is noticed) when the main GFP protected switch trips.
- Location
- Illinois
- Occupation
- retired electrician
Re: Residential service grounding
Brian,
Exception #2 to 250.142(B) permits bonding the grounded conductor to load side meter cans in some cases. One of the cases where this is not permitted is when the main has GFP.
Don
Brian,
Exception #2 to 250.142(B) permits bonding the grounded conductor to load side meter cans in some cases. One of the cases where this is not permitted is when the main has GFP.
Don
G
Guest
Guest
Re: Residential service grounding
This issue has me confused as well. I use Charles R Millers I*llustrated Gui8de to The NEC quite a bit and found this connection shown on page 174 of edition 2 at least and wondered why it is shown that way. Shows egc grounded in the metert base and also in the service panel.Its is also shown on pGE 176 AND 177.tO FURTHER confuse the issue on page 183 they show a clear example of a parralel neutral path. However they do not in that illustration show the egc as grounded in the meter base. Does this mean that is you did ground the neutral it would then eleiminate a parralell path or would the resistance just be reduced to minimize any problem . Interesting question.
This issue has me confused as well. I use Charles R Millers I*llustrated Gui8de to The NEC quite a bit and found this connection shown on page 174 of edition 2 at least and wondered why it is shown that way. Shows egc grounded in the metert base and also in the service panel.Its is also shown on pGE 176 AND 177.tO FURTHER confuse the issue on page 183 they show a clear example of a parralel neutral path. However they do not in that illustration show the egc as grounded in the meter base. Does this mean that is you did ground the neutral it would then eleiminate a parralell path or would the resistance just be reduced to minimize any problem . Interesting question.
Re: Residential service grounding
We have been using rigid nipples ever since I've been an electrician. It is usually 6" to 7" long through the wall and has locknuts on both sides of the meter base and panel. Also plastic bushings are installed on both sides. The gec is terminated in the meter base on the terminal provided. The neutral terminals are factory installed metal to metal to the meter base. Then three insulated conductors are run through and terminated. This obviously creates a parallel neutral in a bonded panel which they are. How else would you go about this installation without using pvc or se cable and romex connectors or bushings? This topic has suddenly baffled me.
We have been using rigid nipples ever since I've been an electrician. It is usually 6" to 7" long through the wall and has locknuts on both sides of the meter base and panel. Also plastic bushings are installed on both sides. The gec is terminated in the meter base on the terminal provided. The neutral terminals are factory installed metal to metal to the meter base. Then three insulated conductors are run through and terminated. This obviously creates a parallel neutral in a bonded panel which they are. How else would you go about this installation without using pvc or se cable and romex connectors or bushings? This topic has suddenly baffled me.
Re: Residential service grounding
The reason I used 5' of RMC was that many installations ( in this locality ) have the panelboard in the basement and it was about 5' of RMC to get from the meter enclosure to the panelboard in the basement.
The over-all point was that many thousands of such installations exist and are being done today that use a metal raceway between the meter enclosure and the Main disconnect, thus a parallel path for the grounded conductor in those installations which do not have a prefectly balance grounded conductor load.
(Does/would any 3W 1? grounded circuit conductor always have a perfectly balanced load so that no load is carried on the grounded conductor? - I doubt it.
The Voltage Drop is ultra low ( in the example ) while the current can be quite high in comparison.
I used resistive loads so that DC formula(s) would be representative, ( in the ball-park ).
At what point would the parallel path values become a problem ?
gwz2
The reason I used 5' of RMC was that many installations ( in this locality ) have the panelboard in the basement and it was about 5' of RMC to get from the meter enclosure to the panelboard in the basement.
The over-all point was that many thousands of such installations exist and are being done today that use a metal raceway between the meter enclosure and the Main disconnect, thus a parallel path for the grounded conductor in those installations which do not have a prefectly balance grounded conductor load.
(Does/would any 3W 1? grounded circuit conductor always have a perfectly balanced load so that no load is carried on the grounded conductor? - I doubt it.
The Voltage Drop is ultra low ( in the example ) while the current can be quite high in comparison.
I used resistive loads so that DC formula(s) would be representative, ( in the ball-park ).
At what point would the parallel path values become a problem ?
gwz2
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