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Detached Garage, 60ft of 10/3 UF-B, New Subpanel, Old knob-and-tube

Detached Garage, 60ft of 10/3 UF-B, New Subpanel, Old knob-and-tube

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  #1  
Old 05-20-14, 04:49 PM
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Detached Garage, 60ft of 10/3 UF-B, New Subpanel, Old knob-and-tube

Hi, I have a detached garage connected with 60ft of 10/3 UF-B to 2-20A breakers on the house load center. I'm replacing knob and tube in the garage, and need to build a small workshop. I suppose I should have one circuit for lights, two for outlets, and leave the rest for the future. Is QO612L100SCP and/or QO816L100SCP appropriate, and/or what are their limitations? Since they have only one 'side', do I only use one hot, or how should I wire it? Should I connect BOTH hots as if they were one, to combat voltage drop? If I want 240v in the future, do I need to use a panel with two 'sides'?
 
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  #2  
Old 05-20-14, 04:58 PM
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You could use two one sided panels, one hot and the neutral into each, but one double sided (120/240 volt) panel would be much better.

You need a master switch for the garage, and the top (double) breaker of a new (2 sided) main panel style panel would be excellent for that. (Panels without top breakers are called lug panels.)

Each side of the 10/3 feed could support two 20 amp branch circuits or one 20 amp circuit plus two 15 amp circuits, although of course the total ampere draw at any given time on each side must not exceed 30 amps.

You may not parallel the garage cable hots to combat voltage drop or for other purposes. The two hots in the garage feed must be connected to opposite sides at your main panel (using a double wide double breaker). It is okay to share the neutral that way.

The old knob & tube wiring may remain in use while it is gradually decommissioned and disconnected. Connect each K&T circuit to a single 15 amp breaker in the new panel (using a length of 14/2 Romex and junction boxes if needed).

The subpanel needs to be grounded with a #6 wire going out to two 8' ground rods at least 6' apart.
 

Last edited by AllanJ; 05-20-14 at 05:25 PM.
  #3  
Old 05-20-14, 05:48 PM
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You need a master switch for the garage, and the top (double) breaker of a new (2 sided) main panel style panel would be excellent for that. (Panels without top breakers are called lug panels.)
The top breaker would be the main breaker in a "Main Breaker Panel" and isn't really called the top breaker because almost all single phase loadcenters can be inverted and bottom fed with the main breaker at the bottom. The same goes for single phase "Main Lug Only" panels, either top or bottom feed them.
 
  #4  
Old 05-20-14, 09:22 PM
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No main shutoff needed if less than 6 breakers in detached sub panel

Others suggest that no main shutoff is needed; are they wrong? http://www.garagejournal.com/forum/a.../t-118923.html
 
  #5  
Old 05-20-14, 10:05 PM
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That would be space for six circuits not six breakers. You could have a panel with 12 spaces and only one breaker and it would still require a disconnect because there is room for 12 circuits. One of the panels you listed is 12 circuit and the other 16 circuit so they would require a disconnect. Neither are 120 only panels. Both are standard 120/240 service panels. However if you use them you will have to use either an unfused air conditioner disconnect (minimum 30a) or use a 30 amp back fed branch circuit breaker with a hold down kit as a disconnect. You will also need to add a ground bar to the panel.

Really don't understand the one side reference. 10-3 UF-b is three wires plus a ground so why would you want to use one side when you have power for both sides?
 
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Old 05-20-14, 10:16 PM
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I have not seen the same as Ray where the need for a disconnect was based on the number of breakers that could be installed versus what is installed at the time of inspection.

IIRC the disconnect needs to be a minimum of 60 amp rated even on a smaller feeder.
 
  #7  
Old 05-21-14, 01:14 AM
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It is a matter of interpretation. IF the panelboard has the ability of serving more than six circuits, even though less than six are originally installed, many inspectors will demand a single disconnecting means. The idea is that it is really easy to install more circuits after the initial inspection.
 
  #8  
Old 05-21-14, 12:57 PM
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the 'one-sided' reference

I thought that only one hot could be used with the two boxes I mentioned, because I assumed they were all connected (the larger boxes have "two sides", on their faces.) Since I only have 10 gauge wire, then if I could use both hots with one of these boxes, that would be preferable; is it possible?
 
  #9  
Old 05-21-14, 01:11 PM
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Go to your local public library and check out some DIY-type books on electricity. On the way home stop at the home improvement center and BUY Wiring Simplified, it will be found in the electrical aisle, not the books and magazines section and will cost about $10. Take these home and READ them. As of now you do not understand wiring systems and that is DANGEROUS. Please do yourself and your family a favor and educate yourself BEFORE attempting this project.
 
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