Aluminum Neutral with Copper Ungrounded Conductors

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ZC'ya

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Colorado Springs, CO
New Member here. I am a third year apprentice, currently laid off at work, enrolled in an IEC school. I've been failed on an inspection, and I'm trying to understand WHY. At work, I have very little common electrician experience, most of my experience is in controls, circuit tracing, and troubleshooting. I have zero residential electrical experience. My parents live just down the street, and called me last week to inform me that their 1966 SquareD QO 100A panel smelled like it was burning. I rushed over to find that they had overloaded the main (dryer, a/c, oven all at once) and the main did not trip. The #2 Aluminum conductor insulation were melted, and the main breaker itself appeared to be slightly melted as well. I had the city come out and remove the meter, and they cut the service loose at the weatherhead. I was able to source a used breaker with the same part number and configuration, and I installed it with new #2 Copper Feeder wire to the meter. Inside the meter socket, there is only one lug in the center for the neutrals. I did not want to land copper in the same lug as aluminum (per 110.14) so I elected to just leave the #2 aluminum neutral in place. The city came back out, reinstalled the meter and reconnected us, told us to have inspected within 72 Hours. Inspector failed the installation, saying we could not use aluminum for neutral and copper for feeders. I have poured over my code book, and cannot find such a restriction. I fear that the only reasonable solution here is to shutdown again, and reinstall #2 aluminum for the feeders...but I can't see how that could be considered better in any way.
 
ZC'ya said:
New Member here. I am a third year apprentice, currently laid off at work, enrolled in an IEC school. I've been failed on an inspection, and I'm trying to understand WHY. At work, I have very little common electrician experience, most of my experience is in controls, circuit tracing, and troubleshooting. I have zero residential electrical experience. My parents live just down the street, and called me last week to inform me that their 1966 SquareD QO 100A panel smelled like it was burning. I rushed over to find that they had overloaded the main (dryer, a/c, oven all at once) and the main did not trip. The #2 Aluminum conductor insulation were melted, and the main breaker itself appeared to be slightly melted as well. I had the city come out and remove the meter, and they cut the service loose at the weatherhead. I was able to source a used breaker with the same part number and configuration, and I installed it with new #2 Copper Feeder wire to the meter. Inside the meter socket, there is only one lug in the center for the neutrals. I did not want to land copper in the same lug as aluminum (per 110.14) so I elected to just leave the #2 aluminum neutral in place. The city came back out, reinstalled the meter and reconnected us, told us to have inspected within 72 Hours. Inspector failed the installation, saying we could not use aluminum for neutral and copper for feeders. I have poured over my code book, and cannot find such a restriction. I fear that the only reasonable solution here is to shutdown again, and reinstall #2 aluminum for the feeders...but I can't see how that could be considered better in any way.
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Have him cite the reference in the NEC. (Hint, there ain't any such reference)
 
pjholguin said:
He may have failed you because your neutral and line conductors are not of the same current ampcity...just a thought. I.e different material.
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He specifically stated that the conductors needed to be made of the same material.

If ampacity is the issue, couldn't I use a 1/0 Aluminum from the meter to the panel and solve that issue without causing a dissimilar metals problem at the neutral lug in the meter socket (Although I might have a problem where I would be landing #2 and 1/0 under the same lug)?

If the sizing is the problem, aren't I permitted to undersize the feeder neutral since it is only carrying the unbalanced load (220.61)?
 
ZC'ya said:
He specifically stated that the conductors needed to be made of the same material.

If ampacity is the issue, couldn't I use a 1/0 Aluminum from the meter to the panel and solve that issue without causing a dissimilar metals problem at the neutral lug in the meter socket (Although I might have a problem where I would be landing #2 and 1/0 under the same lug)?

If the sizing is the problem, aren't I permitted to undersize the feeder neutral since it is only carrying the unbalanced load (220.61)?
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This is another case of an inspector that needs more training. There is no such requirement for the grounded and ungrounded conductors to be of the same material. As long as they are of the correct size they are fine. I did not check your sizes, but you are correct that the grounded conductor does not have to be the same size as the ungrounded as long as the calculations are correct.
 
I have not made any specific calculations at this point to justify the sizing differential, but the #2 aluminum is already good for 100 Amps in a dwelling, so it shouldn't ever be able to carry more than the 100 amps of the main breaker, regardless of the size of the ungrounded conductors.

By design, even if the neutral load exceeds 100 Amps, the main breaker would trip. I understand the branch circuit requirements of same size neutrals to facilitate OCPD opening, but If there were a short to neutral between the meter and the panel, it wouldn't have overcurrent protection anyhow, correct?

Seeing as I am new to this "inspection" process, what can typically be done if the inspector wants to fail you based on misinformation?
 
ZC'ya said:
I have not made any specific calculations at this point to justify the sizing differential, but the #2 aluminum is already good for 100 Amps in a dwelling, so it shouldn't ever be able to carry more than the 100 amps of the main breaker, regardless of the size of the ungrounded conductors.

By design, even if the neutral load exceeds 100 Amps, the main breaker would trip. I understand the branch circuit requirements of same size neutrals to facilitate OCPD opening, but If there were a short to neutral between the meter and the panel, it wouldn't have overcurrent protection anyhow, correct?

Seeing as I am new to this "inspection" process, what can typically be done if the inspector wants to fail you based on misinformation?
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The grounded conductor (neutral) is permitted to be smaller than the ungrounded conductors. Code isn't specific whether 'smaller' is regarding ampacity rating or physical size. The last sentence of 310.15(B)(7) [2011] states, "The grounded conductor shall be permitted to be smaller than the ungrounded conductors, provided the requirements of 215.2, 220.61, and 230.42 are met."

And you are correct, no [premises] overcurrent protection on the POCO side of the service disconnecting means.

If it helps, email the inspector a link to this discussion. If that don't remedy the situation, appeal to his boss or whatever entity is the next higher link in the administrative chain... but choose your battles wisely. Sometimes complying with the inspector is the best course of action, even if he is wrong.
 
My take on this is that, while one must choose their battles, this sounds like an incompetent inspector that is going to cause economic harm to the populace just because he is misinformed. This sounds like an old style meter socket that the neutral used the same lug line and load and to comply with his wishes may require a new meter socket. Next thing you know, now you have to redo the mast to accommodate the new socket, etc. Sounds like the OP made the best of a situation with the funds available and is compliant as described.
While in a perfect world he should just build a whole new service to modern standards as I'm sure that there a million violations by todays standards, that may not be in the cards.
Sorry for the rant, but I just makes me crazy to have some little incompetent bureaucrat thinking he can call the shots.
 
ZC'ya said:
....Seeing as I am new to this "inspection" process, what can typically be done if the inspector wants to fail you based on misinformation?
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Politely ask for a code reference. If he can't (and in this case he won't be able to) give you one then he needs to pass your installation. If he won't then ask how to get in touch with his boss. Don't be a jerk, but don't back down.
 
Agree

Agree

No violation. You should have started a poll, so you could provide the results to the inspector.

Mark
 
I too have done that in the past , In a pinch in the middle of the night I replaced some conductiors at the service mast. The POCO waited on site while I pulled in the new conductors. I only had enough #4 for the 2 hots. Left the AL nuetral that was good. Only 1 hot was damaged.

Behind my back the POCO was telling the Homeowner I was doing it wrong that I needed to use #2 copper and replace the #2 AL also with copper.

Got me pissed. If I had more number 4 CU I would have replaced all, since it was after midnight and the POCO gut was waiting on me I did not go back to the shop ( only a few miles away) time was of the essence. I don't usually have to deal with overhead services in my area as most if not all are underground. I did not know that I was low on #4 CU on the truck.

I talked with the POCO guy a few days and showed him the code book and discussed it . We are on great terms now. He appreaciated learning something.

Hopefully this inspector will learn something too.
 
texie said:
I'm thinking this may be an older socket where the line and load neutral use the same lay in neutral lug.
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A lot of the older round meter sockets here have a center bolt with a compression plate, the neutral conductors are left and right of the center bolt and compressed between the two plates.

Here the electric utility sends out a list of meter sockets that they will except excluding those older sockets from there approved list. Any time a repair is done to a service for any reason that requires the meter seal broken those older sockets are required to be replaced.

We can approve them when re-inspecting services that have been de-energized for a period of time but not if the service is repaired.

It must not be the same way in CO., or the socket would have been required to be replaced.
 
david said:
A lot of the older round meter sockets here have a center bolt with a compression plate, the neutral conductors are left and right of the center bolt and compressed between the two plates.

Here the electric utility sends out a list of meter sockets that they will except excluding those older sockets from there approved list. Any time a repair is done to a service for any reason that requires the meter seal broken those older sockets are required to be replaced.

We can approve them when re-inspecting services that have been de-energized for a period of time but not if the service is repaired.

It must not be the same way in CO., or the socket would have been required to be replaced.
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I am very familiar with those sockets. The AL goes on one side of the screw and the CU on the other. I have one on my house. They are not required to be replaced unless there is a service upgrade. At least in Michigan. And the POCO does not charge for the new ones, you just grab them free off a shelf.
 
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