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Thread: Garage Feeder Q's - Bond Size?

  1. #1
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    Garage Feeder Q's - Bond Size?

    Over 40 yrs ago I ran a 125' 6/3 UF from the main house to a detached garage. I was a "kid" then, not sure I trenched it deep enough, but it's worked up until now just fine

    BUT,,, the other day I lost a leg (every other A/F would trip w/test) 120v on the Red - 0v on the Black at the Mains, 120/120 at the main panel in the house, the junction box where it converts from NM to UF 120/120 at the bugs.

    I have strung an Aerial #2 THHN (TEMPORARILY of course...) and am back up & running quickly. But Now,,, I gotta Fix It...

    I have a buddy who had the remains of a 500' spool of that #2 THHN (he had used less than 100' of it) that I grabbed for the temp repair and he only wanted scrap prices for it ($300) so I will use that for the new feed because it was so cheap. Plus I already have enough 2" PVC to run it in (just have to do the trenching). That's where I'm At for the plans & material, not sure if I'll upgrade to 100A service or continue to feed the #2 with the #6 at the junction box or not (50A has never proved to be an issue so far but upgrading the capacity for the Hardest Part of the run I like).

    So, I want to be smart about this and think of everything first because I only want to do one pull, but I have questions.

    #1 Bond? Do I pull a Green #8 besides the 3 conductors? Bigger maybe?

    #2 Can I pull a 3wire UF with the THHN for expansion (I love to run "spares") Maybe Not a spare, if I ran a 10/3 (in or under the PVC) I might use it for the Generator I run at the Garage (7K) where it's fed from a 30gal "saddle tank" I have there. Right now, I backfeed the Garage breaker in the house, and manually manage the Main when doing so (no transfer s/w or even an Interlock, I could make it an Interlock system by using the 10/3 for that purpose)

    #3 Remember I was a "kid", and at the time my state didn't even accept NM wire but I had another buddy who wired his house in NH and gave me all the NM he had leftover. When I wired this garage (no permits of course) and I Swear this was acceptable somewhere back then, the Bond wire was coiled around the outside of the wire entering the box and clamped by the 2-screw "strain relief" connector (I know,,,). Should I redo all that original wiring now or, if I raise the panel up a foot and put in a ground bar (1970's panel too so later bonds are all on the Neutral bar).

    I CANNOT BELIEVE how expensive all this stuff has become!!! I see that, the roll of THHN I have, is now $1000 and even the PVC would cost over Three Hundred dollars (w/sweeps & LB's). It's Crazy!!!

  2. #2
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    Re: Garage Feeder Q's - Bond Size?

    You are allowed 1 feed to the garage. You might use the 10 for a genset but thats a slightly different issue for the moment. The "green " or the bond wire here needs to be a number 8 minimum and possibly number 6. You can use the number 2, just need to mark it, sizes larger than 6 allowed to be remarked. If I was doing a feed here for gen might be inclined to use another pipe. I would be tempted to buy another wire gor the ground so it fits the lugs. How long is this run?
    Last edited by Sberry; 02-05-2022 at 12:23 PM.

  3. #3
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    Re: Garage Feeder Q's - Bond Size?

    Personally I would not splice your #2 to the #6, but make it a home run all the way.

    I would run at least #6 for the ground, and for the generator I’d run #8 in the conduit to minimize voltage loss.
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  4. #4
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    Re: Garage Feeder Q's - Bond Size?

    The bond in most states is one size smaller than wire you are running.

    There is exception to rule for very long runs where a larger size wire for voltage drop but this typically over 200 feet long and most do not use a larger wire any way.

    If I am using a trenching machine I put everything thing over 24" in ground so nothing will touch the pvc or wire.
    If I am hand digging I use Ridge conduit and go a little over 6" to top of conduit.

    Note I use a rotor tiller with just one side to make digging easier

    Dave

    Quote Originally Posted by BaTu View Post
    Over 40 yrs ago I ran a 125' 6/3 UF from the main house to a detached garage. I was a "kid" then, not sure I trenched it deep enough, but it's worked up until now just fine

    BUT,,, the other day I lost a leg (every other A/F would trip w/test) 120v on the Red - 0v on the Black at the Mains, 120/120 at the main panel in the house, the junction box where it converts from NM to UF 120/120 at the bugs.

    I have strung an Aerial #2 THHN (TEMPORARILY of course...) and am back up & running quickly. But Now,,, I gotta Fix It...

    I have a buddy who had the remains of a 500' spool of that #2 THHN (he had used less than 100' of it) that I grabbed for the temp repair and he only wanted scrap prices for it ($300) so I will use that for the new feed because it was so cheap. Plus I already have enough 2" PVC to run it in (just have to do the trenching). That's where I'm At for the plans & material, not sure if I'll upgrade to 100A service or continue to feed the #2 with the #6 at the junction box or not (50A has never proved to be an issue so far but upgrading the capacity for the Hardest Part of the run I like).

    So, I want to be smart about this and think of everything first because I only want to do one pull, but I have questions.

    #1 Bond? Do I pull a Green #8 besides the 3 conductors? Bigger maybe?

    #2 Can I pull a 3wire UF with the THHN for expansion (I love to run "spares") Maybe Not a spare, if I ran a 10/3 (in or under the PVC) I might use it for the Generator I run at the Garage (7K) where it's fed from a 30gal "saddle tank" I have there. Right now, I backfeed the Garage breaker in the house, and manually manage the Main when doing so (no transfer s/w or even an Interlock, I could make it an Interlock system by using the 10/3 for that purpose)

    #3 Remember I was a "kid", and at the time my state didn't even accept NM wire but I had another buddy who wired his house in NH and gave me all the NM he had leftover. When I wired this garage (no permits of course) and I Swear this was acceptable somewhere back then, the Bond wire was coiled around the outside of the wire entering the box and clamped by the 2-screw "strain relief" connector (I know,,,). Should I redo all that original wiring now or, if I raise the panel up a foot and put in a ground bar (1970's panel too so later bonds are all on the Neutral bar).

    I CANNOT BELIEVE how expensive all this stuff has become!!! I see that, the roll of THHN I have, is now $1000 and even the PVC would cost over Three Hundred dollars (w/sweeps & LB's). It's Crazy!!!

  5. #5
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    Re: Garage Feeder Q's - Bond Size?

    #8 copper (#6 AL) for the equipment ground good up to 100 amps. For the grounding electrode conductor see NEC 250.66 below. Use NEC 250.122 for equipment grounding conductor (EGC) and 250.66 for grounding electrode conductor (GEC). Note that if your GEC is not physically protected the min size is #4 cu
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  7. #6
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    Re: Garage Feeder Q's - Bond Size?

    Thanks for the Input!

    I'm thinking, for the price difference, going with a #6 bond makes sense and, because I do like "running spares", I really like the suggestion that I run spare PVC sounds like a better plan for future (I also have a bunch of 1" I can run along side the 2").

    Trenching, in my area, never involves a Machine I have 40% dirt, 60% rocks, both intertwined with roots through out it All. It's Pick, Bar, & Hatchet with a Narrow Shovel for me (I've done enough digging around here to know how to cope with it...)

    It's just not practical to bring the 2" PVC all the way to the main panel, it's the entire length of the house from where the garage feed will come thru the wall of an, underground "well room" and 15' of slab before the house foundation and why the UF converts to NM in the basement junction box now. I don't know what I'll do when I get there, probably should bring 100A Aluminum to it.

    I have plenty of time to plan for it as the ground is Frozen Solid right now anyway!

  8. #7
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    Re: Garage Feeder Q's - Bond Size?

    Good post on the charts. The reason I mentioned the number 6 was as a disclaimer knowing how forums work due to the footnote on the right-hand chart. As for "spares". If you have something definite planned a spare is ok, you already have pipe but,,, in 40 years of doing this I cant really recall a time I used one or really used any of these future proof schemes. 2 reasons, designs change, stuff becomes obsolete. The best I do and still manage to overkill do mostly to the nature of progress and build as you go but the things I plan way out are really bad, I have 4 circuits and lots of extra wire parked where 1 will do. Did a lot just in case, rolls of wire sitting in pipe where an extension cord would have really worked about as easy and well and sometimes closer than the installed wiring.
    Lights,,, back in the day, quartz 500 watts, now 60. so many cordless tools, about the only thing I use a cord for in storage is an engine block heater on occasion and battery charger. Got 10 circuits,,, just in case,, ha
    Last edited by Sberry; 02-06-2022 at 01:31 PM.

  9. #8
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    Re: Garage Feeder Q's - Bond Size?

    For cutting roots and real messy trenchingI would suggest you get a good carbide toothed reciprocating saw blade. A landscaping buddy recommended this and I was amazed at what quick work it makes of roots, as well as the longevity of the blade (Diablo was that I used).

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