How to wire a sub panel

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  #1  
Old 11-14-15, 09:36 PM
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How to wire a sub panel

I have a 125 amp main panel. I want to install a 100 amp square D sub panel to run a studio apartment above my garage. I was going to use 2/0 AWG copper wire for my 2 hot wires and my neutral wire. I was also going to use a #6 wire to ground the sub panel. I know I do not use the green screw in the sub panel I have already set it to the side. Since I am using individual cables does it have to be in conduit or any thing like that? The sub panel is only about 5 feet from the main panel and it is inside? Any more info would be great. Thanks.
 
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  #2  
Old 11-14-15, 09:50 PM
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Since I am using individual cables
You are not using individual cables. You are using individual wires. A cable is two or more wires in a sheath.
Since I am using individual cables does it have to be in conduit
Yes, because you are not using cable. You are using individual conductors (wires).
 
  #3  
Old 11-14-15, 09:53 PM
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What size conduit? Can I use pvc conduit since it is easier to work with?
 
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Old 11-14-15, 10:02 PM
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Also are my wires I am planning on using, are they the correct size? Am I going about this the correct way? I only want to use copper no aluminum wire.
 
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Old 11-14-15, 10:30 PM
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Size of wire depends on the size of the breaker feeding the panel. If the apartment has gas appliances and heat you may only need a 60 amp breaker and #6 wire. If you are going all electric then you may need 90a or a 100 amp breaker and #2.

Be sure to check the data label on your main panel to see the largest size branch circuit allowed. If it has unused lugs given the distance is less than 6 feet you may be able to connect directly to the lugs instead of to a circuit breaker.

Since the main panel is only 125 amps have you done a load calculation to see if the main panel is large enough? http://www.nojolt.com/load_calculations.shtml

Yes, you can use PVC conduit. 1" should be large enough for #2
 
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Old 11-14-15, 10:50 PM
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I am wanting to use 2 AWG wire from old box to sub panel. In the old box I would use a 100 amp breaker since I am running heavy enough conductor I might as well and new box is a 100 amp box (prefer to have to much and not need it than to need it and not have it) the apartment will be all electric no gas at all. The old box will have nothing ran out of it other than the feeder lines for the sub panel. So I should be okay?
 
  #7  
Old 11-14-15, 11:06 PM
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I am installing a sub panel to wire the apartment because the main panel only has 10 spaces and that is not enough space for me.
(Again I would rather have it and not need it than need it and not have it) the main panel use to power my shop next to the house but we tore it down and moved it to the back and I built a little garage for wife's car and did an apartment above it so I can have a little extra income. My home is wired off a different meter and box all together. So that means that the only thing on this box is going to be the sub panel and it will also be newer. Just trying to clarify so no confusion
 
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Old 11-15-15, 04:30 AM
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You can only have one source of power to the building of the same voltage? That aside, your plan sounds wasteful. Wire into the other panel and install a sub if needed later.
 
  #9  
Old 11-15-15, 05:14 AM
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The box that is there now is not big enough space wise
 
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Old 11-15-15, 05:17 AM
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I am wanting to use 2 AWG wire from old box to sub panel
In your first post you said you were using 2/0 copper and now it's #2. Which is it? By the way, 2/0 cpopper is too big for the lugs on a 100 amp breaker and probably too big for lugs in a 100 amp main lug panel too. I wouldn't use anything bigger than #3 conductors for a short 100 amp feeder.
 
  #11  
Old 11-15-15, 05:26 AM
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2 0 copper will fit in lugs on new box and on breaker no problems there.
 
  #12  
Old 11-15-15, 05:33 AM
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Sub panel help.

I will be installing a 100 amp sub panel in my home I know I have 2 hots a neutral and a ground. I am using 2 AWG wire for both hots and neutral. I am planning on using #6 solid copper for the ground from new box to main box. My question is can I run the ground in the conduit with the 2 hots and neutral? What size conduit do I use? Thanks.
 
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Old 11-15-15, 09:37 AM
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Yes they can be in the same conduit. The ground can be #8 copper.
 
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Old 11-15-15, 10:19 AM
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You will need 1 1/2" conduit.
 
  #15  
Old 11-15-15, 05:13 PM
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What kind of 100 amp breaker is it? I think you are wrong, but if you are sure, go for it.
 
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Old 11-15-15, 05:26 PM
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I will be installing a 100 amp sub panel in my home I know I have 2 hots a neutral and a ground. I am using 2 AWG wire for both hots and neutral
You have 2 threads on this project. In the other thread you said you were using #2 conductors and later in the same thread you were using 2/0 conductors and in the end you were certain 2/0 conductors would fit the lugs on the 100 amp breaker feeding the subpanel. Now you are using #2 conductors again, so which are you really using, #2 or 2/0?

http://www.doityourself.com/forum/el...sub-panel.html
 
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Old 11-15-15, 05:40 PM
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I have merged your threads. Please do not start multiple threads on the same subject.
 
  #18  
Old 11-16-15, 04:06 AM
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I do apologize for the confusion been busy and in a hurry and miss typed some stuff. My plan and my goal would be to run a 100 amp sub panel off of a 125 amp main panel that only has 5 spaces in it. I am wanting to use a sub panel so I have about 20 spaces not all would be used. There will be nothing hooked up in the main panel other than the feeder wire for the sub panel I am looking at using 1 1/2" PVC conduit from one box to the other. 2 0 copper wire for the 2 hot wires and the 1 neutral with #6 solid copper for the ground all ran in the same conduit. There is only about 4.5' between the old box to where I want to put the new box. I also know that I do not use the green bonding screw in the new box. Also know to be sure no paint on the new bus ground bar or on the case where it mounts so it makes a good connection. Am I going about this the correct way? What problems will I run into? Thanks. And sorry for the confusion.
 
  #19  
Old 11-16-15, 05:32 AM
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You can nipple the two panels together and save the wall space. You could also replace the one panel with a larger one.
 
  #20  
Old 11-16-15, 05:40 AM
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What do you mean nipple the 2 boxes together? Never heard,that term or seen it please explain
 
  #21  
Old 11-16-15, 06:40 AM
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Also I just did more research and the breaker I have to use in the main panel is only big enough for 1/0 AWG wire so I will have to use 1/0 AWG stranded black copper THHN it's rated for 125 amps so I should still be okay right?
 
  #22  
Old 11-16-15, 08:01 AM
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the breaker I have to use in the main panel is only big enough for 1/0 AWG wire so I will have to use 1/0 AWG stranded black copper THHN it's rated for 125 amps so I should still be okay right?
You only need #3 for a 100 amp breaker and 100 amps should be okay. Even if you went to 125 you would only need #1 not 1/0.
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Nipple in electrical means the same as it does in plumbing, a short length of pipe or in the case of electrical, conduit. Nipple the boxes together simply means to put them next to each other so you connect them with a nipple.

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Last edited by ray2047; 11-16-15 at 08:41 AM.
  #23  
Old 11-16-15, 08:17 AM
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In conduit #1/0 THHN is good for 150A. For 100A you only need #3 THHN in conduit. For such a short run using wire larger than the minimum is not useful.
 
  #24  
Old 11-19-15, 04:02 AM
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I have decided that I am going to nipple the two boxes together. What size nipple do i need to use? What length and diameter. Do I have to nipple them side by side or can I nipple the new one under the old one so my feeder wire can go straight into the new lugs? Thanks again for all your guys help.
 
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Old 11-19-15, 07:42 AM
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If you are using #3 or #2 1" should be fine for the nipple. Length and position is your option.
 
  #26  
Old 11-19-15, 08:04 AM
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About a 3" length nipple is required to allow the panel covers to fit properly.
 
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