# Corner grounded system



## subelect (Nov 25, 2007)

I know that this will be several dumb questions in one topic, but I have to ask. 
-This morning we went to add on to an existing service for an irrigation well. The POCO added the larger xfmrs and CTs, along with a new service drop down the pole. 

I saw that the POCO had marked the line and load wires on the meter can (center) phase B with white tape and had bonded phase B to the metcan. They connected the bonding jumper on the metcan to the GEC running down the pole with a white #4 stranded. Being an idiot who has never dealt with a corner grounded delta system before, I assumed that it was another single phase, 240 volt system to re-feed the old well and supply the new one we were installing. I was incorrect, it was actually a 3 phase system with no EGC (ground wire). 

I dug up and removed the old conduit; installed a 3 phase w/ ground Terminal Box and reconnected old wires and new 250 aluminum for our 
well motor. I bonded the ground terminal to the box (provided with the TB) and to the GEC, which was the same GEC as the metcan was using. 

Now, my questions:
1. I bonded the TB to the GEC and to its own ground terminal. Should I have also bonded the TB to the metcan? If yes, then do you connect that bonding jumper to the phase B or to the new ground lug that I would have to drill out and install (I didn't see any nomenclature that would allow 2 wires under one lug for phase B)? I realize that phase B was bonded to the metcan, but I want to be sure to understand what is required and what is not allowed. How would you size this bonding jumper?

2. The old well has only the 2 ungrounded and one grounded conductor feeding its disconnect and starter. It had a ground rod and GEC still intact; per the NEC, am I required to dig up the old wires (buried under the corn field) and include a ground wire along with the phase conductors? Realistically, I know that I am not going to do it, but I want to know the requirement.

3. For the new irrigation pump panel, we installed a copper bar in place of a fuse for the phase B grounded conductor (I did not know that they actually sold bars designed to fit fuse holders). What article tells you to do this?

That is about it for the dumb questions. Thanks.


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## nap (Dec 26, 2007)

> I was incorrect, it was actually a 3 phase system with no EGC (ground wire).


POCO never supplies an EGC in any install.




> I dug up and removed the old conduit; installed a 3 phase w/ ground Terminal Box and reconnected old wires and new 250 aluminum for our
> well motor. I bonded the ground terminal to the box (provided with the TB) and to the GEC, which was the same GEC as the metcan was using.


You will have to explain what a "terminal box" is for me to make any sense of this. It is a term not common where I am.



Now, my questions:


> 1. I bonded the TB to the GEC and to its own ground terminal. Should I have also bonded the TB to the metcan? If yes, then do you connect that bonding jumper to the phase B or to the new ground lug that I would have to drill out and install (I didn't see any nomenclature that would allow 2 wires under one lug for phase B)? I realize that phase B was bonded to the metcan, but I want to be sure to understand what is required and what is not allowed. How would you size this bonding jumper?


terminal box?




> 2. The old well has only the 2 ungrounded and one grounded conductor feeding its disconnect and starter. It had a ground rod and GEC still intact; per the NEC, am I required to dig up the old wires (buried under the corn field) and include a ground wire along with the phase conductors? Realistically, I know that I am not going to do it, but I want to know the requirement.


well, if you aren't going to do it, does it really matter what is the correct install?





> 3. For the new irrigation pump panel, we installed a copper bar in place of a fuse for the phase B grounded conductor (I did not know that they actually sold bars designed to fit fuse holders). What article tells you to do this?


the one that says you cannot disconnect the grounded conductor without also disconnecting all the ungrounded conductors. If using fuses, it woud be possible to blow the fuse on B phase without popping either of the others and this would be disconnecting the grounded conductor but not disconnecting the ungrounded conductors.


> That is about it for the dumb questions.


there aren't too many dumb questions when you are dealing with something that will kill you if you screw it up.


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## JohnJ0906 (Jan 22, 2007)

subelect said:


> I know that this will be several dumb questions in one topic, but I have to ask.
> -This morning we went to add on to an existing service for an irrigation well. The POCO added the larger xfmrs and CTs, along with a new service drop down the pole.
> 
> I saw that the POCO had marked the line and load wires on the meter can (center) phase B with white tape and had bonded phase B to the metcan. They connected the bonding jumper on the metcan to the GEC running down the pole with a white #4 stranded. Being an idiot who has never dealt with a corner grounded delta system before, I assumed that it was another single phase, 240 volt system to re-feed the old well and supply the new one we were installing. I was incorrect, it was actually a 3 phase system with no EGC (ground wire).


Is this new service a different system from the old one? You had better check EVERYTHING there to make sure it is compatible.





> Now, my questions:
> 1. I bonded the TB to the GEC and to its own ground terminal. Should I have also bonded the TB to the metcan? If yes, then do you connect that bonding jumper to the phase B or to the new ground lug that I would have to drill out and install (I didn't see any nomenclature that would allow 2 wires under one lug for phase B)? I realize that phase B was bonded to the metcan, but I want to be sure to understand what is required and what is not allowed. How would you size this bonding jumper?


If on line side of service disconnect, 250.66. 



> 2. The old well has only the 2 ungrounded and one grounded conductor feeding its disconnect and starter. It had a ground rod and GEC still intact; per the NEC, am I required to dig up the old wires (buried under the corn field) and include a ground wire along with the phase conductors? Realistically, I know that I am not going to do it, but I want to know the requirement.


What was the voltage of the old pump? 240v 1 ph? If so, use one existing conductor for an EGC.




> 3. For the new irrigation pump panel, we installed a copper bar in place of a fuse for the phase B grounded conductor (I did not know that they actually sold bars designed to fit fuse holders). What article tells you to do this?


240.22


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## subelect (Nov 25, 2007)

POCO never supplies an EGC in any install.


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## subelect (Nov 25, 2007)

Sorry about my last post; fumble fingers. 

First of all, I appreciate your inputs and I am not trying to sound argumentative. I am going to try to answer your questions without being a wise-guy.

_POCO never supplies an EGC in any install._
The POCO will drop a #4 stranded or solid, uninsulated copper wire down the pole and put it in a curly-cue at the bottom of the pole before they install it in the hole. This is their version (IAW their rules) of an EGC and electrode.

_You will have to explain what a "terminal box" is for me to make any sense of this. It is a term not common where I am._
A terminal box is nothing more than a steel box with insulated connection points for multiple wires of the same phase. The top of it can be fitted with a hub or blank, the bottom and sides have various size knock outs. Out here in the boonies, we usually put a 300 or 600 volt TB below the meter can or disconnect so that you can feed several agricultural buildings from one central pole. It makes it easy to kill power to a building in case of fire. 

_well, if you aren't going to do it, does it really matter what is the correct install?_
I feel the need to be familiar with the requirements before I decide to go to a lot of unnecessary work or if I have to upgrade something that could be a big expense for the customer. 

_Is this new service a different system from the old one? You had better check EVERYTHING there to make sure it is compatible._
Roger that.

_If on line side of service disconnect, 250.66._ 
Customer did not want a disconnect below the meter can; each individual well has its own disconnect. The bonding jumper that I asked about would be on the load side of the meter, but the phase B is not broken by meter stabs. 

_What was the voltage of the old pump? 240v 1 ph? If so, use one existing conductor for an EGC._
240 volt, 3 phase. 

Thanks again for taking the time to answer my questions.


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## nap (Dec 26, 2007)

.



> _POCO never supplies an EGC in any install._
> _The POCO will drop a #4 stranded or solid, uninsulated copper wire down the pole and put it in a curly-cue at the bottom of the pole before they install it in the hole. This is their version (IAW their rules) of an EGC and electrode._


they do not bring an EGC to the service. 



> _You will have to explain what a "terminal box" is for me to make any sense of this. It is a term not common where I am._
> _A terminal box is nothing more than a steel box with insulated connection points for multiple wires of the same phase. The top of it can be fitted with a hub or blank, the bottom and sides have various size knock outs. Out here in the boonies, we usually put a 300 or 600 volt TB below the meter can or disconnect so that you can feed several agricultural buildings from one central pole. It makes it easy to kill power to a building in case of fire._


So, this is merely a junction box used for tap connections. 



> _well, if you aren't going to do it, does it really matter what is the correct install?_
> _I feel the need to be familiar with the requirements before I decide to go to a lot of unnecessary work or if I have to upgrade something that could be a big expense for the customer. _


hopefully you are pre-'08 code since that one is out in my truck and I can't check it. The same rules apply here (in '05 code) as with any other seperate building situation. You can bring a ground, or not. The main diff is grounded conductor and grounding electrode system is not bonded at the remote panel if you do bring an EGC or is bonded if you do not being an EGC.






> Customer did not want a disconnect below the meter can; each individual well has its own disconnect. The bonding jumper that I asked about would be on the load side of the meter, but the phase B is not broken by meter stabs.


don't you think it wise to have a disco at the drop point?




> _What was the voltage of the old pump? 240v 1 ph? If so, use one existing conductor for an EGC._
> _240 volt, 3 phase. _


then what has changed? You stated the old sub had two ungrounded and one grounded conductor and since the pump was 3 phase, you already had a 3 phase grounded delta service.



> Customer did not want a disconnect below the meter can; each individual well has its own disconnect. The bonding jumper that I asked about would be on the load side of the meter, but the phase B is not broken by meter stabs.


 so you are telling me that all the underground runs have no way of disconnecting them from the main dist point should there be a problem with them? HHmm, I have seen some pretty big resistance heaters made this way.

so, what all hasn't been answered? I've lost track.


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## subelect (Nov 25, 2007)

Nap,
The remaining questions that I have are:
Since the meter can and terminal box are both bonded to the same GEC, do they need to be bonded together? 
What section of the NEC says that you can grandfather stuff and do not have to bring it up to new code as long as it was good back in the day and does not pose an imminent threat?
Besides speaking directly to the POCO, is there a definitive way of looking at a 3 phase, corner grounded system and knowing that it is not a classic single phase, 3 wire (residential) system? When the POCO wrapped phase B with white tape, that was where I made my mistake; I assumed it was the grounded conductor. My boss happened to see my error and correct me (frickin' sux). 
Thanks again.


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## nap (Dec 26, 2007)

> Since the meter can and terminal box are both bonded to the same GEC, do they need to be bonded together?


they are bonded by the GEC already. what else do you want?




> What section of the NEC says that you can grandfather stuff and do not have to bring it up to new code as long as it was good back in the day and does not pose an imminent threat?


None that I am aware of. That is a local jurisdiction thing. The NEC is the direction at the time of installation, which would include alteration. If you are altering parts of a system, you are in effect causing a new install and that install must be to current code. Your AHJ has final say as to what is grandfathered or not.




> Besides speaking directly to the POCO, is there a definitive way of looking at a 3 phase, corner grounded system and knowing that it is not a classic single phase, 3 wire (residential) system?


real simple (sort of). 240 to ground=delta 3 phase; 120 to ground= single phase 120/240. there is no 120 volts with a corner grounded delta. (unless you have a POCO that supplies 3 ph 120 volt delta but I have never seen or heard of it)



> When the POCO wrapped phase B with white tape, that was where I made my mistake; I assumed it was the grounded conductor.


No mistake; it IS the grounded conductor.



> My boss happened to see my error and correct me (frickin' sux).


 Ya, but if you smoked a couple grand worth of equipment, it would have sucked more.

I had a thesis typed up here but it seemed confusing so I trimmed it back. Anymore questions; ask.


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