1/0 AWG aluminum wiring

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Old 10-25-07, 03:35 PM
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1/0 AWG aluminum wiring

I am planning to upgrade my main/service entrance panel to 200amps. Presently my panel has two, two pole breakers, one is 100amp that feeds the subpanel for the house and the other is a 40amp breaker which serves the A/C circuit. I wish to add a third 60 amp breaker to supply a subpanel in my detached garage. My current (no pun intended) Bryant main panel only has room for four circuits (2 two pole breakers) and hence the reason for my upgrade. The meter does however appear to have 200amp markings. I may already have 200amp service and not know it.
I noticed the underground cable coming from my utility company to the meter is 1/0 AWG aluminum wiring. Is this conductor sufficient for my planned upgrade to 200amps?
Is there any additional grounding requirements or is removing and replacing a main panel all there is to it? (after calling my utility company for service shut off of course)
This work will be checked by a building inspector.
Thanks in adavce for your help and expertise.
 
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Old 10-25-07, 03:54 PM
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Originally Posted by upflying View Post
1/0 AWG aluminum wiring. Is this conductor sufficient for my planned upgrade to 200amps?
No, Al #1/0 is good for a maximum of 125A in a dwelling service; possibly 100A if the distance is longer than 100' or so. A 200A service requires a minimum of #4/0 aluminum or #2/0 copper; upsized accordingly if there is a long distance involved.

Is there any additional grounding requirements or is removing and replacing a main panel all there is to it?
Yes. The service grounding and bonding needs to be updated at the same time as a service upgrade. This will require a #4 copper GEC from the main panel to the water service entrance (if municipal water supply) and an additional one or two ground rods, well casing, foundation ground, etc.

Often the meter pan and service conduit needs to be changed to accommodate the new service as well.
 
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Old 10-25-07, 04:40 PM
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I think that you will find that the utility company (which is not governed by the National Electrical Code) will tell you that theirwire is sufficient for a 200 amp service.
I don't think that I have ever seen anything larger than 1/0 for a 200 amp service on the line side of the meter. Typically, it is even smaller.
Per Table 310.15(B)(6), 1/0 aluminum is allowed for up to 175 amps so they are not that far off from 200.
However, once you get to the load side of the meter (customer's), you will have to install either 2/0 copper or 3/0 aluminum.
I just finished a 400 amp service today that the utility fed with 4/0 aluminum.
The Code we follow says that 4/0 is good for 200 amps in a residential setting.
When we do power studies for generators, we typically only see a peak of about 65 amps at any given time on a 2,000 square foot house.
Chances are you meter is okay because you either have a 150 or 200 amp service already in place.
 
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Old 10-25-07, 05:36 PM
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i also think too that a lot of service providers install a 200 amp meter, even though you may only have a 100 amps coming in off the street. there is really no price difference between the two meters, so maybe they figure give the customer the higher amp meter planning for future upgrades.. and i think too a 3/0 is the minimum for copper for 200 amp service. i just did my house and got a 3/0 copper which is rated 200 amp with a 75 degree centigrade insulation.
 
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Old 10-25-07, 05:53 PM
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Please check the Code article (Table 310.15(B)(6) that I referenced in my post and you will find that 2/0 copper is rated for 200 amps on a residential service.
3/0 copper is required for installations other than 120/240, single phase dwelling services and feeders.
Why spend the extra money?
Let's be careful to give people the proper advice when it comes to installations that are governed by The National Electrical Code.
 
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Old 10-25-07, 05:58 PM
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Originally Posted by KAL444 View Post
i also think too that a lot of service providers install a 200 amp meter
Originally Posted by KAL444 View Post
.. and i think too a 3/0 is the minimum for copper for 200 amp service.
KAL, it is not good enough to "think". You need to "know".

The meter itself is TOTALLY irrelevant to the consumer. The POCO uses what they want/require. We install the meter pan according to the size of the service.
Most every new meter installed residentially is a "200CL" meter. It will work for 60, 100, 200 amps.

3/0cu is NOT the minimum size for a 200A residential service.



Originally Posted by KAL444 View Post
i just did my house and got a 3/0 copper which is rated 200 amp with a 75 degree centigrade insulation.
We do NOT use 310.16 for sizing residential services. We use 310.15(B)(6) which allows the use of 2/0cu or 4/0al for a 200A residential service.


Flying, your POCO is the ONLY one who can tell you if the underground is adequate. Some POCOs provide this cable, some do not. If they provide it it is their call if it is big enough.
POCOs live by their OWN rules, NOT the NEC.
 
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Old 10-26-07, 09:30 AM
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Thanks for the education, I'm learning a lot. After posting this yesterday, I had a chat with my building inspector. He agrees that 1/0 AWG is not sufficient for a 200amp service upgrade. He said upgrading the conductor to 3/0 or 4/0 will also mean upgrading the conduit from the street. He implied that means trenching, obviously a huge expense and a long time without power . After telling him what I am doing, his suggestion was to replace my existing 100amp main panel with a 125amp "distribution panel" that has additional spaces for breakers. This would simply be a "remove and replace" with no need to upgrade the 1/0 conductor. He also said that my 25 year old home should have a ground called a "u-fer" and there is no need to upgrade my ground. I'm not sure what a u-fer is but he said simply reattaching the ground to the new panel is all that is needed. The inspector gave me information on how to contact my utility company to shut off my power. He said the utility company will not energize the new panel until he inspects my work. He also told me that plugs in garages must be 18" from the floor not the 12" I have them mounted at presently. He also wanted to see flourescent lighting in my new garage. I had planned incandescent but he said some new code will require it. Still lots to learn.
 
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Old 10-26-07, 09:48 AM
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Plugs 18 inches from the floor must be a local requirement. In an garage I recommend just over 48 inches, so that a piece of plywood against the wall won't cover any, and so that they are easier to reach.

"...some new code will require it" does not mean that it is required now. You should still pass with incandescent lighting until such time as the code changes, and then it won't catch you retroactively. However, if you plan on being in the garage for long periods of time, I would still go with fluorescent, required or not.
 
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Old 10-26-07, 06:51 PM
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The size of the incoming line to your meter is a decision of your power company, not the inspector.
If you really want to upgrade, have them take a look at it.
I am confident that they will be content with the 1/0 that is there.
What size wire is installed from the meter to your panel at the present time?
Is it large enough to just "replace" your current panel?
What is the rating of the panel you have now?
If you are basing your new service size on this infamous 1/0 conductor size, you can go to 175 amp per the NEC.
 
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Old 10-28-07, 08:29 AM
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Originally Posted by dezwit View Post
The size of the incoming line to your meter is a decision of your power company, not the inspector.
If you really want to upgrade, have them take a look at it.
I am confident that they will be content with the 1/0 that is there.
What size wire is installed from the meter to your panel at the present time?
Is it large enough to just "replace" your current panel?
What is the rating of the panel you have now?
If you are basing your new service size on this infamous 1/0 conductor size, you can go to 175 amp per the NEC.
Dez, I have a 100amp main panel now. I am removing the main panel because it only has four spaces for breakers. Both are two pole breakers which are 40amp for the a/c and 100 amp for the house subpanel. I need another space for a 60amp breaker to feed a subpanel in a detached garage. I purchased a Cutler Hammer 125amp main panel with a meter socket and 12 spaces. I think I am all good now, I'll let you know how it goes.
 
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Old 10-28-07, 08:52 AM
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Originally Posted by dezwit View Post
If you are basing your new service size on this infamous 1/0 conductor size, you can go to 175 amp per the NEC.

The OPs 1/0 conductor is aluminum, not copper. Only good to 125 a.

In addition, the dmark between utility and customer is different depending on where you live. The local inspector is very likely to know the laws in your area. I suggest he/she is correct in the advice given.
 
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Old 10-28-07, 10:53 AM
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JWhite,
Thank you, I stand corrected.
Next time I will put my glasses on and turn on the lights.
 
 

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