A question on Sub Panels

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Old 11-12-12, 08:58 PM
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A question on Sub Panels

My house has 200 amps supply. I have two 125 amp breaker box's that supply my house, there are no unused circuit breakers. These two box's are direct wired from the street..... meaning one of them is not a sub panel. I want to build a detached Workshop supply 100 amp 240v. And I also want to finish my basement. My question is how is the best way to handle this? I was thinking of expanding one of my existing main panels and converting it to a 200 amp. This new 200 amp should have plenty of power for the added features in the basement as well as adding a sender 100 amp that would tie to the sub panel in the detached workshop. Is this the best way to approach this problem? Or should I just add two 125 sub panels, one for inside the house to power the basement and one to power the workshop?
 
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Old 11-13-12, 12:08 AM
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You have a 200 amp service with two 125 service panels and they are full. How many breakers are there in those panels ? One of them cannot be the main panel because then it would be a 200 amp panel. The best way for us to help you is to take a picture of both panels with the doors open for starters. One picture for each panel. A picture of each panel with their covers off would be extra helpful.


You could have two 125 amp main panels if they were common fed from a trough below them.
 
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Old 11-13-12, 06:22 AM
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Take the garage feed from whichever panel has a lesser load on it. How old are these panels? I'm guessing they're pretty old as they didn't just use one 200A panel.
 
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Old 11-13-12, 05:16 PM
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How do you know you have a 200 amp supply? You said the two 125 amp panels are direct fed from the street, do they each have their own 125 amp feeder from the street? Where is the meter? Is there a 200 amp breaker or fusible disconnect at the street? By street, I am assuming you mean from the utility pole at the street; is that correct?
 
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Old 11-13-12, 09:56 PM
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I thought it was odd with 2 125 as well. I didnt realize that you could have essentially a splice at the meter to feed the two boxes equally. Am I wrong in that assumption? See photos
 
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Old 11-13-12, 10:01 PM
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I looked on the outside of my house at the Meter. It states in big and bold numbers and letters 200 amps. I havnt seen a 200 amp fuse yet entering the house but will look for one in the morning.
 
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Old 11-14-12, 07:09 AM
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Pix of the outside breaker at the meter

Well after taking a good look at the outside breaker box at the meter on the house, I confirmed I have a 200 amp cb supplying the house. But, I also discovered that my two breaker boxes are fed only 100 amp each. So, correct me if Im wrong, that means that my main breaker box is the outside box next to the meter (this houses the 200 amp cb and the two 100 amp sender cb's) that feed the two Sub Panels in my basement that act to what I thought was my main Circuit Boxes? Also I then would think that my problem would be a little simpler now. I should be able to put in another 100 amp sender circuit breaker in my exterior main breaker box to directly feed the new Sub panel out to my proposed detached workshop. Is this correct?
 
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Old 11-14-12, 07:20 AM
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Sorry guys, Im just learning this stuff. Im trying to get my head straight as to what is going to be needed. Looking at this picture I see a 200 amp main breaker and then 2 double pole 100 amp breakers. Is this correct? What is throwing me is that each half of the double poles are listed 100, so for a second I was thinking maybe these could be 200 amp double pole breakers. Please correct my thinking.
 
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Old 11-14-12, 07:34 AM
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No, the numbers on the handles are not added. If it says 100a it is 100a. What you have is a 200 amp main service supplying two 100a subpanels. You should do a load calculation to see if 200 amps is going to be enough for your needs. Here is one load calculator Single Family Dwelling Electrical Load Calculator but I can't vouch for its accuracy. You might want to Google for a couple of more and compare the results.
 
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