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Thread: Sub-panel grounding question and a GFCI breaker question

  1. #1
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    Sub-panel grounding question and a GFCI breaker question

    My long-awaited basement wiring job is finally underway. I'm using a 100A main panel as my sub; it's adjacent to the house panel and will be fed by a 60A breaker. The pre-installed 100A breaker will be used as a disconnect only. I'm planning on using 6-3 nm-b copper wire to feed the sub (approximate wire length: 6'-7').

    Question 1:
    Will a new grounding rod be required for this panel? I think the answer is no, but I've read a few different things that have me questioning my research.

    Question 2:
    Since this is unfinished space, I believe code requires everything except for dedicated outlets to be GFCI protected. I can buy one 60A GFCI breaker for about $100, or I can pick up individual 20A breakers for $30 per. Since I'm making 2 separate runs to 3 rooms plus another single run to each of 3 more rooms, the second option will cost around $300. Aside from cost, is one of these options better than the other? If I'm running two 10A or 15A tools from circuits on one leg of the power, will that cause problems with the GFCI? I'm pretty sure it's not a problem, but once again I figured I'd ask while the asking's good

    I don't think I can use a GFCI outlet to protect the entire run:
    I'm running all wires 18"aff. Single gang boxes are placed every 6' or so: it's an attempt to meet finished space codes if I decide to finish the rooms. At each single gang box, a splice / pigtail is run to a double box at 50" aff for my shop outlets. Per my current plan, all of the outlets are on brances from the main line; none of them are (currently) able to interrupt the entire chain.

    Bonus question: How the heck do people manage to wire nut 3 or 4 12ga wires? I've had a hard time pig-tailing the wires at each junction. I've resorted to holding the wires with one set of smooth jaw pliers, twisting them around 3-4 times with another set of pliers, and then cutting off all but 1/2" of the twisted connection. If I get lucky and the wire doesn't unravel, I can get the wire nuts on.

    Thanks!
    Jay M

  2. #2
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    AFAIK, no additional ground rod would be needed as long as your sub is not in a separate building. I would use 20A GFCI breakers in your sub rather than a 60A GFCI breaker at the main. I have a similar set up and asked that same question on an electrical forum, and it seems like the pros thought I would experience nuisance trips if the GFCI were in the main panel. To join multiple 12ga wires, I strip off at least and inch of insulation and use a big pair of linesman's pliers to twist them together. Then use the pliers to clip of the ends of the twisted wires so that the wire nut can cover all of the exposed conductors.

  3. #3
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    Code requires that most sub panels be grounded through the main panel. You will need to remove the bonding between the neutral and ground buss in your sub panel, and run an isolated ground from the sub panel ground buss to the main panel ground.

  4. #4
    Ground wire will only need to be a #10, if I remember correctly. I would do differently. Run feed to higher recpts. (GFCI) and drop down to lower ones from the above. This way you don't have to "dig" to get to tripped GFCI. GFCI recpts area lot cheaper than GFCI breakers.

  5. #5
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    I had a similar situation but I finished the basement. No separate grounding rod was required, and I had to disable the connection between the nuetral and ground busses in the subpanel. Then connect the ground buss from the subpanel to the ground on the main panel. I also had to groung the box of the subpanel. They make a kit for this, but I used 12ga copper from the ground buss in the subpanel and a screw through the back of the box.

    I'm not sure about the GFCI requirement you mention, maybe true. The inspector told me that all unfinished areas had to have at least one GFCI in them. I have a storagae area that stayed unfinished and had to install a GFCI outlet. All of my garage outlets are protected by a single GFCI outlet and I believe it is considered "unfinished" space even though it is sheetrocked. The 120 outlets in my shop are not GFCI protected, and it is probably considered "unfinished" as well (OSB walls, sheetrock ceiling, concrete floor). All of it has passed electrical inspection.

    I hired a licensed electrician for a couple of hours to help me layout the electrical and plan it. I also hired him to install and set the subpanel. It was money well spent for my skill level.

    Mike

  6. #6
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    Thanks guys.
    I've removed the neutral / ground bonding strip, and will move the box bonding lug from the neutral to the ground bus so that I can tie it to the panel box (grounding the enclosure).

    Quote Originally Posted by Scott T Smith View Post
    Code requires that most sub panels be grounded through the main panel. You will need to remove the bonding between the neutral and ground buss in your sub panel, and run an isolated ground from the sub panel ground buss to the main panel ground.
    Just to be clear: this is covered by the #10 ground wire in the 6-3nm cable, correct?



    Quote Originally Posted by Bruce Wrenn View Post
    Ground wire will only need to be a #10, if I remember correctly. I would do differently. Run feed to higher recpts. (GFCI) and drop down to lower ones from the above. This way you don't have to "dig" to get to tripped GFCI. GFCI recpts area lot cheaper than GFCI breakers.
    Good plan, bad timing . Almost all of my runs are complete and ready for outlets. I had no idea the GFCI breakers were so expensive when I started laying everything out. Oops.

    The only way I can interrupt the flow is to add an extra box and GFCI outlet at the front of each circuit. Not a problem for some of the circuits, but it won't work for a couple of the others. I'll look at it again this weekend to see where I have space to drop them in and where I'm stuck using breakers.


    Quote Originally Posted by Brad Sperr
    To join multiple 12ga wires, I strip off at least and inch of insulation and use a big pair of linesman's pliers to twist them together. Then use the pliers to clip of the ends of the twisted wires so that the wire nut can cover all of the exposed conductors.
    I must have wimpy fingers. I can only twist them if I use another pair of pliers to hold everything.

  7. #7
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    Quote Originally Posted by Jay Maiers View Post
    Bonus question: How the heck do people manage to wire nut 3 or 4 12ga wires? I've had a hard time pig-tailing the wires at each junction. I've resorted to holding the wires with one set of smooth jaw pliers, twisting them around 3-4 times with another set of pliers, and then cutting off all but 1/2" of the twisted connection. If I get lucky and the wire doesn't unravel, I can get the wire nuts on.

    Thanks!
    Jay M
    I just recently started using these and they work very well. No more twisting and they are very quick to install.
    I Pledge Allegiance to This Flag, And If That Bothers You Well That's Too Bad - Aaron Tippin

  8. #8
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    Quote Originally Posted by Jay Maiers View Post
    Just to be clear: this is covered by the #10 ground wire in the 6-3nm cable, correct?
    Correct, the #10 ground wire in a cable typically used in 60A service is no coincidence, it's just the right size. I concur with everyone else regarding the grounding and it sounds like you've got a good handle on that.

    Depending on your local electrical code the outlet requirements are all over the place. In general, all 120V outlets in an unfinished space must be GFCI protected, the cheapest option being a single GFCI outlet as the first device in each branch circuit. If you are putting in any 240V outlets you don't have to worry about GFCI on those. Some outlets which may be exempt from GCFI depending on your local codes are single outlet receptacles being used by a single device that blocks access to the outlet and is not easily moved (eg. fridge or freezer). Depending on how your state and local building departments have adapted the NEC code any outlet below about 5' off the ground must be tamper resistant and any outlets in bedrooms may need to be arc-fault protected (didn't sound like you had any finished bedrooms yet). It really irked me to install tamper resistant outlets in my garage 4' off the ground, but rules are rules.

    You can join 4 #12 wires using the twist and snip method and using a red wire nut.

  9. #9
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    Quote Originally Posted by Steve Meliza View Post
    It really irked me to install tamper resistant outlets in my garage 4' off the ground, but rules are rules.



    I hope I don't have a pile of worthless outlets. I bought most everything I would need about a year and a half ago...

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