What size service ? How to tell ?

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Stevenfyeager

Senior Member
Location
United States, Indiana
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electrical contractor
My customer has two 200 amp panels, and thinks his house he just bought has 400 amps, and wants me to add quite a bit of loads. But I have seen houses have 200 amp panels before and yet have only 200 service. The meter base is a large, 400 amp sized one. But, the conduit coming up from the ground is only 2 inch, which around here is not large enough, they always require 2 1/2 to 3 inch. So I called the POCO. They have it listed as a 200 amp service. (We are not allowed in IN to remove the meter.)
What determines the service amp size anyway ? Is there theoretically an 'infinite' amount of amps available from the pole, limited only by the main breaker in the house ?
Thank you.
 
Stevenfyeager said:
My customer has two 200 amp panels, and thinks his house he just bought has 400 amps, and wants me to add quite a bit of loads. But I have seen houses have 200 amp panels before and yet have only 200 service. The meter base is a large, 400 amp sized one. But, the conduit coming up from the ground is only 2 inch, which around here is not large enough, they always require 2 1/2 to 3 inch. So I called the POCO. They have it listed as a 200 amp service. (We are not allowed in IN to remove the meter.)
What determines the service amp size anyway ? Is there theoretically an 'infinite' amount of amps available from the pole, limited only by the main breaker in the house ?
Thank you.
Click to expand...

If there is only one 2" pipe to this house, the best is 200 amps based on my memory. It sounds like the house had future in mind with a 320 amp meter (400) Amps
The service wire will ultimately determine what the max size panels, equipment, and load...
You may have to run another 2" to the transformer based on what you have described.
 
Stevenfyeager said:
My customer has two 200 amp panels, and thinks his house he just bought has 400 amps, and wants me to add quite a bit of loads. But I have seen houses have 200 amp panels before and yet have only 200 service. The meter base is a large, 400 amp sized one. But, the conduit coming up from the ground is only 2 inch, which around here is not large enough, they always require 2 1/2 to 3 inch. So I called the POCO. They have it listed as a 200 amp service. (We are not allowed in IN to remove the meter.)
What determines the service amp size anyway ? Is there theoretically an 'infinite' amount of amps available from the pole, limited only by the main breaker in the house ?
Thank you.
Click to expand...

When I worked for the poco, we specified a 2” or 3” pipe for underground residential services. 90% of the time it was 2”. A 200 amp residential service will seldom draw anywhere *near* 200. (Yes, I know it can happen.)

If you saw a 2” pipe on an underground residential service on our system, it had one of four possible URD triplex conductors in it: 1/0, 2/0, 3/0, or 4/0. 80% of them were 1/0. That’s 1/0 *aluminum* feeding a “200 amp” service. I don’t recall one ever burning up.

All that said, if I were you, I’d get with the poco again and tell them what you have planned. If it’s a smart meter, they should have good load info available. You may well find that despite the small pipe, there’s enough capacity in their wire for the load additions you are looking at.
 
Everytime I call my POCO and tell them I am upgrading a service and they should come out and put a bigger service drop in they ignore me. Go ahead and use 400 amps if you have a properly wired 400 amp service. If the service drop burns up, it' POCO's problem.
 
I did a service last year 10 sets of 500s Poco fed the service with one set of 4/0

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OP, to summarize what others are saying, the size of your service is determined by the main breaker/breakers. The size of the service entrance conductors to the the connection point of the service lateral needs to be sized per the NEC. As in, based on load calculations per article 220. The service lateral and that which the utility owns and provides, is not covered by the NEC. You are responsible to do load calculations, and submit them to the AHJ and/or the POCO as required. What is done from there is out of your hands. However, as a thorough and conscientious contractor I would feel obligated to let my customer know that the POCO may need to upgrade their service, and if I had any suspicion that the incoming service lateral was too small, I would do a voltage drop test after energizing.
 
The service is 400 amps in spite of what the power company brings to the site. If there are issues with the load then it would be their responsibility to fix it.
 
If this is on the power companies side to install, all bets are off. It's a 400 amp service based on your equipment side and wire.

Add the loads!
 
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