Sub Panel Help Needed


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Old 03-23-14, 03:46 PM
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Question Sub Panel Help Needed

Hello experts. I need to find out if it is out of code to run my sub panel feed line through the same hole as the main lug 4-0 service conductor at my main box. OK, that's about as clear as mud.

So, picture this...my main 200 amp box in my house (actually a lug as the main breaker is outside) has its aluminum service line coming in at the top of the box as most services do. There is ZERO room for any more wires to come through the top as all of the knock outs are knocked out. There are no knock outs on the sides on the cheap Square D box they used when the house was rewired. So, I have no room to run the 2-2-2-4 aluminum SER wire to my sub panel. It looks like I could fit the new SER wire through the same hole as the main supply wire at the top (the 4-0 aluminum that brings power into the house), but I cannot find out if that is a "bad" thing to do.

If it is a bad thing to run two big wires through one hole, I am left with removing sheet rock and feeding the sub panel from the bottom of the main lug. I do plan to have all of this inspected, but I really do not want to pay an electrician $800 plus parts for running a line 50 feet. However, I do want to do this right, and I have a good bit of electrical experience.

Your help is appreciated!
 
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Old 03-23-14, 04:02 PM
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I'm guessing a standard squeeze connector at the top of the panel like in picture below.
That connector is rated for one cable only.

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Also.... your sub panel must connect to a breaker sized to the cable you are running (100A).
If you were to use lugs off the main bussbars.... then you would have to run 200A cable.
 
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Old 03-23-14, 04:04 PM
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That is exactly what mine looks like. So, it looks like I will be taking the long way around.

Thanks for your time
 
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Old 03-23-14, 04:08 PM
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Missed the part at the bottom. I plan to use a 100 Amp breaker attached to the main box to supply power to the sub panel. I have a 30 amp breaker for an air compressor that I plan to delete to make room for the 100 amp breaker that will feed the 2-2-2-4 supply line to the sub.
 
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Old 03-23-14, 04:24 PM
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Why do you need 100 amps? The size of the subpanel does not determine the size of the feed except to limit the maximum feed. 60 amps is usually adequate for a work shop. Nothing you have posted indicates you need more.
 
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Old 03-23-14, 05:02 PM
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Ray,

I am planning to run a Lincoln Square Wave tig welder on a 50 amp circuit, my compressor on a 30 amp circuit, a 30 amp 110 circuit for power tools that draw a bunch of amps, and a 20 amp circuit to a storage sheds for lights and smaller tools.

In reality, 60 amps might work, as I can only do one thing at a time. What do you think?
 
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Old 03-23-14, 05:22 PM
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a 30 amp 110 circuit for power tools that draw a bunch of amps,
General purpose 120 volt circuits are limited to 20 amps.

Why can't you come out the bottom of the panel? Where is the sub panel going? Attached or detached structure? Is the 2-2-2-4 SER or Quadplex? As mentioned you cannot come through the same connecter as the 4/0 wire/cable.
 
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Old 03-23-14, 05:30 PM
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The panel is fed via the attic, and sheet rocked in. My access to the panel is inside the second floor of my home. So, going through the bottom means ripping out some rock, and then routing the conductor back through the attic about 50 feet over to the garage ceiling. The sub is going in my garage (a converted carport but fully enclosed and attached). The 2-2-2-4 is SER, as that is what the electrical supply store recommended. I do plan to add lights to my detached shed from the sub in the garage. The 30 amp circuit was put in as a double pole breaker (slow blow only one hot used?) by a contractor for a 110 welder that I used.
 
 

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