How to get a Formal code interpritation ?

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acrwc10

Master Code Professional
Location
CA
Occupation
Building inspector
I did a job several months ago and at final inspection ( on a new house 7300 sq ft.) the inspector said the ground to the water service was under sized and wanted it run in a larger size. The panel was a Sq D homline 400 amp meter main combination, this panel has two 200 amp breakers fed from the meter socket by using parallel 3/0 copper (factory wired) I ran a #2 copper. The inspector wanted 1/0 copper.
It was the last day before the house was to get turned over to the home owners and we needed the house final inspection signed off. So after trying to explain, how he was misreading the code, I just ran in 1/0.
Now that this job is over and done, I want to get a formal interpretation on this from the code makers. How do I go about doing this ?

Just to fill in the blanks, I sized my ground base on the combined cross sectional mills of parallel 3/0 and the fact that our local POCO (PG&E) had run 350 KCMIL aluminum for service conductors, under ground fed. The water service is copper for 50+ feet to the house. If the meter socket to breakers had been bussing, instead of cable, I would have run 1/0.
I feel this was a Bad call, but I have asked at least 3 other building inspectors what they would say and they felt 1/0 is the correct size. There stand "the label on the panel says 400 amps so you need a 1/0 cu. ground". At the time we couldn't wait for a formal interpretation, now I just want official clarification for future installs.
 

kwired

Electron manager
Location
NE Nebraska
I did a job several months ago and at final inspection ( on a new house 7300 sq ft.) the inspector said the ground to the water service was under sized and wanted it run in a larger size. The panel was a Sq D homline 400 amp meter main combination, this panel has two 200 amp breakers fed from the meter socket by using parallel 3/0 copper (factory wired) I ran a #2 copper. The inspector wanted 1/0 copper.
It was the last day before the house was to get turned over to the home owners and we needed the house final inspection signed off. So after trying to explain, how he was misreading the code, I just ran in 1/0.
Now that this job is over and done, I want to get a formal interpretation on this from the code makers. How do I go about doing this ?

Just to fill in the blanks, I sized my ground base on the combined cross sectional mills of parallel 3/0 and the fact that our local POCO (PG&E) had run 350 KCMIL aluminum for service conductors, under ground fed. The water service is copper for 50+ feet to the house. If the meter socket to breakers had been bussing, instead of cable, I would have run 1/0.
I feel this was a Bad call, but I have asked at least 3 other building inspectors what they would say and they felt 1/0 is the correct size. There stand "the label on the panel says 400 amps so you need a 1/0 cu. ground". At the time we couldn't wait for a formal interpretation, now I just want official clarification for future installs.

Table 250.66 is fairly black and white in my opinion.

You have parallel 3/0 service entrance conductors this equals 335,600 circular mills. table says for 3/0 to 350 copper you need #2 copper or 1/0 aluminum GEC.

I have never seen a label on a panel that stated what size GEC to run. It is not a requirement to have a GEC for each and every panel installed for one thing. 250.66 is the rule here.

edit: actually you do not really have service entrance conductors but in this case you still use the equivalent value of what would be required for the purpose of sizing GEC see note 2 T250.66.
 
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acrwc10

Master Code Professional
Location
CA
Occupation
Building inspector
You would think it is that easy, but even though the Service entrance conductors where already in, he said "what if the POCO changes them in the future". So you can see I was not talking to a person with an open mind.
 

Hameedulla-Ekhlas

Senior Member
Location
AFG
I did a job several months ago and at final inspection ( on a new house 7300 sq ft.) the inspector said the ground to the water service was under sized and wanted it run in a larger size. The panel was a Sq D homline 400 amp meter main combination, this panel has two 200 amp breakers fed from the meter socket by using parallel 3/0 copper (factory wired) I ran a #2 copper. The inspector wanted 1/0 copper.
It was the last day before the house was to get turned over to the home owners and we needed the house final inspection signed off. So after trying to explain, how he was misreading the code, I just ran in 1/0.
Now that this job is over and done, I want to get a formal interpretation on this from the code makers. How do I go about doing this ?

Just to fill in the blanks, I sized my ground base on the combined cross sectional mills of parallel 3/0 and the fact that our local POCO (PG&E) had run 350 KCMIL aluminum for service conductors, under ground fed. The water service is copper for 50+ feet to the house. If the meter socket to breakers had been bussing, instead of cable, I would have run 1/0.
I feel this was a Bad call, but I have asked at least 3 other building inspectors what they would say and they felt 1/0 is the correct size. There stand "the label on the panel says 400 amps so you need a 1/0 cu. ground". At the time we couldn't wait for a formal interpretation, now I just want official clarification for future installs.

What was the distance from source to the equipment. There is also one hint in NEC ground size due to voltage drop. When cable size increases due to voltage drop, it affects your ground size too. Have you noticed that one?
 

Volta

Senior Member
Location
Columbus, Ohio
What was the distance from source to the equipment. There is also one hint in NEC ground size due to voltage drop. When cable size increases due to voltage drop, it affects your ground size too. Have you noticed that one?

Do you mean 250.122(B)?

That is for EGCs, rather than GECs. But that thinking is why 250.66 is based on Ungrounded Conductor size rather than OCP. It would be nice if they did that for the EGC table too.
 

acrwc10

Master Code Professional
Location
CA
Occupation
Building inspector
What was the distance from source to the equipment. There is also one hint in NEC ground size due to voltage drop. When cable size increases due to voltage drop, it affects your ground size too. Have you noticed that one?
Apples and bowling balls. The GEC is based on the size of the service conductors, if there is a "choke" in the system in the form of a smaller conductor ( say for example parallel 3/0 ) the fault/lightning/what ever is also going to be "choked" at that point.

Do you mean 250.122(B)?

That is for EGCs, rather than GECs. But that thinking is why 250.66 is based on Ungrounded Conductor size rather than OCP. It would be nice if they did that for the EGC table too.

incressing the EGCs when the ungrounded conductor size is incressed makes perfect sense, if it takes a larger wire to get the voltage out there, it is going to take a larger wire to get it back and clear the fault.
 

Hameedulla-Ekhlas

Senior Member
Location
AFG
Apples and bowling balls. The GEC is based on the size of the service conductors, if there is a "choke" in the system in the form of a smaller conductor ( say for example parallel 3/0 ) the fault/lightning/what ever is also going to be "choked" at that point.



incressing the EGCs when the ungrounded conductor size is incressed makes perfect sense, if it takes a larger wire to get the voltage out there, it is going to take a larger wire to get it back and clear the fault.

Yeah, artical 250.122(B) is wrong for this but when they ask you to increase the size. Did you ask them why or did they convince you that you did or as they said and you did without any reason. Didnt you ask him why or any code reference to convince you.
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
Table 250.66 is fairly black and white in my opinion.

You have parallel 3/0 service entrance conductors this equals 335,600 circular mills. table says for 3/0 to 350 copper you need #2 copper or 1/0 aluminum GEC.

edit: actually you do not really have service entrance conductors but in this case you still use the equivalent value of what would be required for the purpose of sizing GEC see note 2 T250.66.


The OP says there is parallel 3/0 conductors in the meter main combo. I have seen combo units with actual wires rather than a buss. Note #2 would apply only if there was a buss bar instead of conductors.

If you use Note #2 the the GEC would need to be 1/0.
 

kwired

Electron manager
Location
NE Nebraska
You would think it is that easy, but even though the Service entrance conductors where already in, he said "what if the POCO changes them in the future". So you can see I was not talking to a person with an open mind.

POCO may change the service lateral but this is not the service entrance conductors. from the meter to the service disconnect would be the service entrance conductors and in your case you have to use note 2 and use the equivelant size of conductor required.

why is the POCO going to increase the size unless you upgrade the service capacity then the GEC will likely need increased anyway?

how much increase does he want you to allow for? Maybe better plan for 2000 amp service just in case:mad:
 

Volta

Senior Member
Location
Columbus, Ohio
The OP says there is parallel 3/0 conductors in the meter main combo. I have seen combo units with actual wires rather than a buss. Note #2 would apply only if there was a buss bar instead of conductors.
I guess I have to agree that Note #2 does not apply when the meter is on the line side of the disconnect. I don't think it matters if the conductors are wire or bar in shape, though.
If you use Note #2 the the GEC would need to be 1/0.
We don't know what the load is. If it is 351 to 400 amps, the 3/0 wires would be sufficient, but Note #2 does use a singular for 'conductor', so parallel is not intended for the equivalent size. That would mean a 500 or 600 kCM depending on load, so again I agree that would need to be a 1/0 AWG.

In this application though, as Note #2 cannot be used, two 3/0 wires are allowed, and T250.66 shows that a #2 AWG is ok.
 
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kwired

Electron manager
Location
NE Nebraska
The OP says there is parallel 3/0 conductors in the meter main combo. I have seen combo units with actual wires rather than a buss. Note #2 would apply only if there was a buss bar instead of conductors.

If you use Note #2 the the GEC would need to be 1/0.

This may be true. According to note 2 you may also be able to run a #2 depending on the load to be served.

Depending on the difficulty of installing the GEC to the water service I probably would not fight inspector over it. I would give him my opionon if I disagree with him and not just give up.

I have done service upgrades on older buildings where the water and electric services are a long distance apart and this can be a big deal. Most new buildings seem to bring all utilities in the same room or at least same area so everything is close and not too big of a problem to change it.
 

acrwc10

Master Code Professional
Location
CA
Occupation
Building inspector
This may be true. According to note 2 you may also be able to run a #2 depending on the load to be served.

Depending on the difficulty of installing the GEC to the water service I probably would not fight inspector over it. I would give him my opionon if I disagree with him and not just give up.

I have done service upgrades on older buildings where the water and electric services are a long distance apart and this can be a big deal. Most new buildings seem to bring all utilities in the same room or at least same area so everything is close and not too big of a problem to change it.

Maybe you could expand on this comment. The way I read it, it all has to do with wire/buss size and notheing to do with the load. If you had a 60 amp load fed with 500 MCM copper the GEC would be sized for the 500MCM not the 60 amp load.
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
As far as the thread title. In reading 90.4 I would think the answer is :"The authority having jurisdiction for enforcement of the Code has the responsibility for making interpretations of the rules" so the Building Official for the Governmental agency that adopted your Code would be your "formal interpretor"
My opinion would be that if you ask 100 inspectors, 95 will stick with the 1/0.
Table 250.66 in the column heading states "Based on the Service Entrance Conductor" . Few inspectors are going to consider a factory installed and sized "jumper" in a distribution board the service entrance conductor.
You have a 400 amp service which would have a minimum size conductor from 310.15(B)(6) at 400 kcmil Cu.
 

e57

Senior Member
~~~~
I feel this was a Bad call, but I have asked at least 3 other building inspectors what they would say and they felt 1/0 is the correct size. There stand "the label on the panel says 400 amps so you need a 1/0 cu. ground". At the time we couldn't wait for a formal interpretation, now I just want official clarification for future installs.
Maybe they all went to the same circus school??? Or inspecting over the phone most likely...

I'll inspect it over the phone too....
I'll make the assumption this was a dwelling - with a class 320/400 service - meter main enclosure.... I'll assume they will run 350MCM AL (Page 3)
Then I'll look at 250.66 - find 250-500 AL = either #2Cu, or 1/0 Al - I'll look to see which is there - see copper - expect it to be #2 - and confirm if required. Now while the POCO conductors may or may not have been there - #2Cu for an electrode covers a huge range on Al conductors - None of which are rated to take 400A, all but one sized for 320... Lacking SEC's one could very well say - you should up it to 1/0 - but that person would also have little experience with the POCO (PG&E) and not know that they are going to pull 350 Al and likely nothing else... Now if I was punchy that day - I might like you to point out the parallel 3/0 and prove that to me too - but that is if I was being punchy - and if I were an inspector at all.... I'm sure there would be many who were glad I were not.... :D But I would have let it at #2... Since it's not really a 400a service...
 

kwired

Electron manager
Location
NE Nebraska
Maybe you could expand on this comment. The way I read it, it all has to do with wire/buss size and notheing to do with the load. If you had a 60 amp load fed with 500 MCM copper the GEC would be sized for the 500MCM not the 60 amp load.

I was talking about note 2 to the table.

2. Where there are no service-entrance conductors, the grounding electrode conductor size shall be determined by the equivalent size of the largest service-entrance conductor required for the load to be served.

the note says where there are NO service entrance conductors.

If you have no service entrance conductors the 500MCM you mentioned does not exist.

How about if you had gear with 600 amp buss feeding it but only have 250 amps of load connected to it but have 2 to 6 breakers installed as your mains? Assume there is no article 310 conductor supplying this,but a buss.

Someday you may add load to this and then the equivelant conductor is larger but that will need to be resolved at that time just like the same installation would be allowed to run a article 310 250 amp conductor but need changed if increasing the load.
 

kwired

Electron manager
Location
NE Nebraska
Look at these definitions from art 100

Service-Entrance Conductors, Overhead System. The service conductors between the terminals of the service equipment and a point usually outside the building, clear of building walls, where joined by tap or splice to the service drop.

Service-Entrance Conductors, Underground System. The service conductors between the terminals of the service equipment and the point of connection to the service lateral.

FPN: Where service equipment is located outside the building walls, there may be no service-entrance conductors or they may be entirely outside the building.

Service Equipment. The necessary equipment, usually consisting of a circuit breaker(s) or switch(es) and fuse(s) and their accessories, connected to the load end of service conductors to a building or other structure, or an otherwise designated area, and intended to constitute the main control and cutoff of the supply.

Service Lateral. The underground service conductors between the street main, including any risers at a pole or other structure or from transformers, and the first point of connection to the service-entrance conductors in a terminal box or meter or other enclosure, inside or outside the building wall. Where there is no terminal box, meter, or other enclosure, the point of connection is considered to be the point of entrance of the service conductors into the building.

Service Point. The point of connection between the facilities of the serving utility and the premises wiring.
 

Dave58er

Senior Member
Location
Dearborn, MI
IMO the #2 is all that is required however you look at it.

I haven't seen this type of meter before so I am having a hard time picturing how you have parallel conductors. The 3/0 wires join at the meter then split off and feed separate 200 amp breakers right?

310.4 says "......(electrically joined at both ends)."

(emphasis mine)

As kwired mentioned this install makes me think of gear when you have a large bus, say 1000 amps, but one of the service disconnects is joined to it with smaller cooper bus "fingers" that adapt the smaller breaker to make it reach the large bus. Your 3/0 are like those "fingers".
 

e57

Senior Member
Assume there is no article 310 conductor supplying this,but a buss.
Technically there is the 3/0... This type of panel has the meter socket, then two sets of 3/0 THHN/THWN away from it to 2 main breakers... (Factory installed ;))

IMO the #2 is all that is required however you look at it.

I haven't seen this type of meter before so I am having a hard time picturing how you have parallel conductors. The 3/0 wires join at the meter then split off and feed separate 200 amp breakers right?

310.4 says "......(electrically joined at both ends)."

(emphasis mine)

As kwired mentioned this install makes me think of gear when you have a large bus, say 1000 amps, but one of the service disconnects is joined to it with smaller cooper bus "fingers" that adapt the smaller breaker to make it reach the large bus. Your 3/0 are like those "fingers".

The meter he's describing is like this - But instead of the 2 parallel sets of 3/0 to one 400a breaker - it is a set of 3/0 conductors to each of 2 200A mains. Not handle-tied either. (I use them a lot.) They are not parallel.... Meant to feed two separate feeders... It is technically IMO not a 400A service - it's a 320continuous/400Max meter and enclosed adjacent to it is two 200A services... ;) Nor will the POCO feed it in conductors larger than 350MCM Al.
 
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