Adding Garage Sub Panel

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  #1  
Old 03-13-13, 12:13 PM
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Adding Garage Sub Panel

I want to add some circuits for my workshop equipment but my main panel is maxed out. I was thinking of adding a sub about 3 foot away from it to connect the new circuits. In order to supply the sub I will have to move two breakers from the main and add them to the sub to create space for the breaker feeding the sub. In moving the two ciruits can I just move the 2 lives and leave the nuetral and grounds alone in the main?

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Old 03-13-13, 12:32 PM
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Welcome to the forums!

In moving the two ciruits can I just move the 2 lives and leave the nuetral and grounds alone in the main?
No. All of the conductors supplying any one circuit must be contained within the same raceway. That means either the same cable or conduit.

Are you sure you need to add a subpanel? How many spaces does your existing panel have in it? Will your existing panel accept tandem breakers? If so, how many are installed now?

If you do need to add a subpanel, it must be supplied from a 240V breaker in the main panel, so that's another two full-height spaces you will need to make in your existing panel. Your subpanel will need the standard clearance space in front of it, just like your existing panel. Unlike your existing panel, most likely, the neutrals will have to be isolated and the grounds will have to be bonded in the subpanel.
 
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Old 03-13-13, 03:59 PM
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Thank you for the response. The main is full and no spaces to add. I would have to move two breakers to the sub in order to create a 240 space for the feeder.
 
  #4  
Old 03-13-13, 06:20 PM
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the neutrals will have to be isolated and the grounds will have to be bonded in the subpanel.
Which means you'll need 4 wires to feed the subpanel; 2 hots, 1 neutral and 1 ground. You'll also have to add an accessory ground bar to the subpanel and DO NOT bond the neutral bus to the panel box. Your new circuits will have the grounding conductors terminate on the new ground bar and the neutral conductors terminate on the neutral bar. To move 2 circuits to the subpanel to make room for the breaker to feed the subpanel, I would suggest pulling those cables from the main panel and installing them into the subpanel.

Who is the manufacturer of the main panel and how old is it. It's entirely possible you just need to replace the main panel with a larger one.
 
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Old 03-13-13, 07:45 PM
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Who is the manufacturer of the main panel and how old is it. It's entirely possible you just need to replace the main panel with a larger one.
Also, what size service do you have and what size panel are you thinking of adding?
 
  #6  
Old 03-17-13, 06:56 PM
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Sorry for the delay in responding. The panel is a Eaton MBED204OB200BF and was installed 2012. The main is 200A. This is a 2,700 sq foot home and they maxed out the panel because we have 5 bedroom, 2 kitchens, 2 laundries and 3 bathrooms. This is what they call a NextGen home with a seperate granny/in-law apartment within the same floorplan. The daily load is high and everything is tandem breakers. My problem is there is no spare space to add a "workshop" panel. I would have to remove some circuits and move them to the sub. I was thinking I need a minimum of 40A for the sub allowing for moving some circuits to the sub in order to create a space. What size feeder would I need for a sub as I think 6-3 maybe a lot bigger than necessary.

Thank you to the group!
 
  #7  
Old 03-17-13, 08:22 PM
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The model number you gave for your existing panel does not match Eaton's designations. Can you check it again, or post a picture of the label on the inside of the cover?

I was thinking I need a minimum of 40A for the sub allowing for moving some circuits to the sub in order to create a space. What size feeder would I need for a sub as I think 6-3 maybe a lot bigger than necessary.
To determine the appropriate size for the subpanel, do a load calculation.

For a 40A load you need #8 AWG copper conductors. For a 60A load you need #4 AWG. The #6 AWG you mentioned is rated for up to 50A.

You will need to use NN-3/G cable or 4 individual conductors in conduit.
 
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