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garage sub-panel

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  • #373403
    thedude306
    Moderator
    Foam Lake, SK

    I have a 10/3 wire out to the garage. Currently it is using one side for lights and the other for plugs. Ground is ran back to the house panel. I want to get 240V out there for DC.

    Can I just add a sub panel with 4 breakers running off a 30amp 240V breaker? One 15 amp for lights, one 20 amp for plugs and two 15amp for 240? Disconnect the ground wire and install a 8′ a ground rod at the garage?

    The 10/3 is already there under ground and will be a PITA to change.

    Any other suggestions?

    Brad T
    Self employed Pro since 2014!!

    #373406
    kurt@welkerhomes.com
    Moderator
    Owatonna, MN - Minnesota

    I think this belongs in crazy electrical stuff you have seen, just kidding, I don’t think I would use the ground as a current carrying conductor or rely on just a ground rod. My guess is that the safe way to do it is a new conductor with 3 line and a ground conductor.

    #373413
    thedude306
    Moderator
    Foam Lake, SK

    I think it’s all to code as it is! LOL I “think”

    I am pretty sure it’s supposed to have a new ground rod and shouldn’t be using the ground with the 10/3 cable like it is after you add a sub panel.

    Might have to get the local sparky involved so I don’t melt down the garage…

    Brad T
    Self employed Pro since 2014!!

    #373414
    TonyG
    Pro
    Colorado Springs, CO

    You can do that. It will be small, ampacity wise, for a sub panel and you may overload it.
    You would not disconnect the ground you have to utilize all the wires. If I am understanding you correctly and we call 10/3 the same thing lol. There should be a black, red, white and bare wire?

    How it is required to be done where I am for a subpanel, is you have to separate the grounds and neutrals and add the ground rods if it is a detached building.

    #373426
    smallerstick
    Pro
    North Bay, ON

    I have a 10/3 wire out to the garage. Currently it is using one side for lights and the other for plugs. Ground is ran back to the house panel. I want to get 240V out there for DC.

    Can I just add a sub panel with 4 breakers running off a 30amp 240V breaker? One 15 amp for lights, one 20 amp for plugs and two 15amp for 240? Disconnect the ground wire and install a 8′ a ground rod at the garage?

    The 10/3 is already there under ground and will be a PITA to change.

    Any other suggestions?

    Thank you for this question. I hadn’t thought about it before but I guess I’m in close to the same position you are.
    I have a 6/3 underground to my garage running a sub panel for 110 and 220 outlets. 220 is for the TS only (16A).

    Question about the ground, though, should I have a separate ground for the shop sub-panel?

    BE the change you want to see.
    Even if you can’t Be The Pro… Be The Poster you’d want to read.

    #373449
    Lakelover
    Pro
    Fort Qu'Appelle, SK

    I would call a Sparky. The grounding can be a grey area. When I ran my subpanel to the house from the shop (priorities) I was massivly confused and hired it out.

    Also what is your distance of run ? if it gets to long you must consider voltage drop.

    I almost dropped by your place today, but I took a different highway as I had to go to Regina and pick up new glasses.

    #373458
    Seven-Delta-FortyOne
    Pro
    The Emerald Triangle, Northern California

    Sorry, grounding is not a grey area. It is very specific, and very detailed in the code. It is also complicated.

    What you are calling a 10-3, is this red, black, and bare, or red, black, white and bare? Big difference.

    Please, DO NOT, under any circumstances, disconnect the ground, and rely on a ground rod. Here is the complicated part; a ground rod is not what is used for grounding a system. The center tap on the transformer is the ground point. So ALL grounds must return to the main disconnect, where the neutral is also bonded.

    If you had 2 hot wires, one neutral, and a ground rod, you would have a ” bootleg” ground, where the neutral is also the ground. This is grandfathered in in some VERY specific instances, and is deadly if certain criteria are not met.

    Delta

    Goin' Down In Flames........

    #373462
    58Chev
    Pro
    Etobicoke, ON

    Remember to remove the “Bonding Strap” in the sub-panel.

    I would not use the grounding rod at the garage but have the ground run from the main.

    Good info in this document >> http://www.allsafehomeinspection.com/Inspecting%20the%20Subpanel.pdf

    “If you don’t pass on the knowledge you have to others, it Dies with you”
    — Glenn Botting

    #373551
    Seven-Delta-FortyOne
    Pro
    The Emerald Triangle, Northern California

    Don’t know what code cycle you are on, but ground rods are required at sub panels in my area.

    They are, however, not the return path for ground fault current.

    Delta

    Goin' Down In Flames........

    #373728
    thedude306
    Moderator
    Foam Lake, SK

    It’s a pretty short run. About 20 feet or so. The 10/3 is red/black/white with bare copper.

    Building is detached and requires an 8′ ground rod by code here. Talked to a electrician and my understanding is I use everything but don’t bond the neutral and ground in the sub panel and add the ground rod.

    The wire is under interlocking brick in a metal conduit. I was doing some math and I have a feeling I am going to need to run a larger wire. I am going to see if I can pull a 6/3 through but I don’t think it will fit so I may dig it up.



    @Lakelover
    the house is at a standstill. Engineers and building inspectors caused to much of a delay so it’s going in next spring.

    Brad T
    Self employed Pro since 2014!!

    #373733
    smallerstick
    Pro
    North Bay, ON

    Remember to remove the “Bonding Strap” in the sub-panel.

    I would not use the grounding rod at the garage but have the ground run from the main.

    Good info in this document >> http://www.allsafehomeinspection.com/Inspecting%20the%20Subpanel.pdf

    That helps a lot. Thanks for the link.

    BE the change you want to see.
    Even if you can’t Be The Pro… Be The Poster you’d want to read.

    #373734
    JimDaddyO
    Pro
    Wawa, ON

    I finally got hold of an electrician for my shop build. I will post the details in my thread when he comes to have a look. I am in Ontario, but I think code would be similar, and the situation is similar, though a bit longer distance from the house.

    My You Tube channel: https://www.youtube.com/channel/UCA5AretE3xPoVDV61AxUdUA

    I don't do a fast job. I don't do a slow job. I do a half fast job.

    #373735
    Sprokitz
    Pro
    Eastern shore of, Pa

    I think it’s all to code as it is! LOL I “think”

    I am pretty sure it’s supposed to have a new ground rod and shouldn’t be using the ground with the 10/3 cable like it is after you add a sub panel.

    Might have to get the local sparky involved so I don’t melt down the garage…

    Some inspectors will fail cable in conduit. They want individual wires. If they do allow it, it will have to be UF

    #373773
    Anonymous
    Inactive

    I had a similar situation when I wired up my 240v hot tub on the back patio, I came off the main breaker box from the house by adding another double 240v breaker. Ran the #6g individual wires up through the attic and down the eve in conduit to a sub panel box mounting on the back of the house, Ran three wires. Two 110v hots and a neutral to a single breaker in the sub and on to the hot tub also in conduit, Then at the sub panel they told me to add a ground rod. I think it’s unbonded, I remember something about you only want one grounding rod per system. when I got it all done I hired an electrician to come inspect it for safety reasons, Took him 5 minutes and $75 to tell me it’s correct. But it wouldn’t pass code simply cuz I ran the individual wires through the attic without conduit, Hope that helps

    #373778
    Seven-Delta-FortyOne
    Pro
    The Emerald Triangle, Northern California

    I had a similar situation when I wired up my 240v hot tub on the back patio, I came off the main breaker box from the house by adding another double 240v breaker. Ran the #6g individual wires up through the attic and down the eve in conduit to a sub panel box mounting on the back of the house, Ran three wires. Two 110v hots and a neutral to a single breaker in the sub and on to the hot tub also in conduit, Then at the sub panel they told me to add a ground rod. I think it’s unbonded, I remember something about you only want one grounding rod per system. when I got it all done I hired an electrician to come inspect it for safety reasons, Took him 5 minutes and $75 to tell me it’s correct. But it wouldn’t pass code simply cuz I ran the individual wires through the attic without conduit, Hope that helps

    Well, you only want one ground point, which is at the main disco, but you can have as many ground rods as you wish.

    Some systems have whole grids of ground rods tied together with wire. I did a 50kv GenSet in a sawmill, and we put I think 8 or 10 rods under the slab, and connected in a grid with exothermic welds.

    Wire outside of conduit is a definite no-no. The sheathing on THHN wire, for example, is not designed to stand up to physical abuse.

    Cable in conduit is a pet peeve of mine. There is absolutely nothing in the code prohibiting it, in fact, there are many instances where it is required, yet every inspectigator I know of won’t allow it. I’m tired of arguing with them, so unless I absolutely have to sleeve a cable, I’ll install a J-Box and switch to wire.

    The 10-3 you described is exactly what you would need for a sub-panel, however, 10-3 is only good for 30 amps in that situation.

    You can install a sub-panel, have a 30 amp breaker protecting it, and put as many breakers as you wish in the sub. However, you will never have more than 30 amps to use.

    Delta

    Goin' Down In Flames........

    #373780
    Lakelover
    Pro
    Fort Qu'Appelle, SK

    @thedude306………..the house is at a standstill. Engineers and building inspectors caused to much of a delay so it’s going in next spring.

    What the heck??? Who is giving you grief ? The RM, who is contracted for inspections?

    I just got head hunted to do a large ICF project at Kateptwa Lake. I’m pretty sure I know who is going to inspect that job, the guy is firm but does understand ICF etc.

    How many deer running around you place ? Bow season is approaching.

    #373782
    Anonymous
    Inactive

    Well, you only want one ground point, which is at the main disco, but you can have as many ground rods as you wish.

    Some systems have whole grids of ground rods tied together with wire. I did a 50kv GenSet in a sawmill, and we put I think 8 or 10 rods under the slab, and connected in a grid with exothermic welds.

    Wire outside of conduit is a definite no-no. The sheathing on THHN wire, for example, is not designed to stand up to physical abuse.

    Interesting on the ground rods, Seems like I found out later if I would have ran a fourth wire I wouldn’t have needed it??? And yeah I really wish I would have known about the conduit thing through the attic dang it, I would’ve had no problem doing that with like the flexible type.

    When I wired my enclosed trailer for 120v my electrician neighbor made me use……………crap I forgot what it’s called but it’s three wires already in a metal flexible conduit, that stuff sucked to cut but I guess it’s a lot better protected than just romex

    #373783

    It’s a pretty short run. About 20 feet or so. The 10/3 is red/black/white with bare copper.

    Building is detached and requires an 8′ ground rod by code here. Talked to a electrician and my understanding is I use everything but don’t bond the neutral and ground in the sub panel and add the ground rod.

    The wire is under interlocking brick in a metal conduit. I was doing some math and I have a feeling I am going to need to run a larger wire. I am going to see if I can pull a 6/3 through but I don’t think it will fit so I may dig it up.

    @Lakelover the house is at a standstill. Engineers and building inspectors caused to much of a delay so it’s going in next spring.

    Sounds like you have everything you need to make it a legit install. I would try it on the wiring you have. Like @Seven-Delta-FortyOne said as long as you don’t exceed the 30 amps you are fine. Good thing is @ only 20′ voltage drop isn’t and issue for you.

    Andrew

    A Working Pro since 1995!

    Member since March 26, 2014.

    #373804
    Seven-Delta-FortyOne
    Pro
    The Emerald Triangle, Northern California

    Interesting on the ground rods, Seems like I found out later if I would have ran a fourth wire I wouldn’t have needed it??? And yeah I really wish I would have known about the conduit thing through the attic dang it, I would’ve had no problem doing that with like the flexible type.

    Well, not really.

    I’ll try to explain ground rods.

    The grounding on a panel returns to the center tap on the utility transformer, which is grounded. This is also the neutral conductor. Not all neutrals are grounded, but in residential, the grounded conductor will always be the neutral. In some 3-phase industrial installations, one of the three phases is the grounded conductor. This is why in the Code, there is a difference between a ‘grounded’ conductor, and a ‘grounding’ conductor.

    Back to grounding. All the grounding conductors return to the main panel, where they are tied into the grounded conductor, which is the neutral. This is the low impedance path that will allow many thousands of amps to flow in a matter of milliseconds, and so open an overcurrent device.

    The ground rods are a secondary return path for overcurrent, going back to the center tap of the utility transformer, which is also grounded. It also dissipates stray voltages, and greatly helps to dissipate lightning strikes. It helps to balance a system, because it is a good reference point of zero potential. But the Code states that the earth may not be used as the return path for grounding purposes.

    This is why “grounding” is not accomplished using only ground rods. A wire connection back to the grounded neutral is the main grounding system.

    This is also why neutrals and grounds are separated everywhere but at the main disco, because if they were connected, there would be multiple return paths for current, and high likelihood of electrocution from touching anything that is bonded in the structure.

    I hope I didn’t further confuse the issue.

    Delta

    Goin' Down In Flames........

    #373808

    Interesting on the ground rods, Seems like I found out later if I would have ran a fourth wire I wouldn’t have needed it??? And yeah I really wish I would have known about the conduit thing through the attic dang it, I would’ve had no problem doing that with like the flexible type.

    Well, not really.

    I’ll try to explain ground rods.

    The grounding on a panel returns to the center tap on the utility transformer, which is grounded. This is also the neutral conductor. Not all neutrals are grounded, but in residential, the grounded conductor will always be the neutral. In some 3-phase industrial installations, one of the three phases is the grounded conductor. This is why in the Code, there is a difference between a ‘grounded’ conductor, and a ‘grounding’ conductor.

    Back to grounding. All the grounding conductors return to the main panel, where they are tied into the grounded conductor, which is the neutral. This is the low impedance path that will allow many thousands of amps to flow in a matter of milliseconds, and so open an overcurrent device.

    The ground rods are a secondary return path for overcurrent, going back to the center tap of the utility transformer, which is also grounded. It also dissipates stray voltages, and greatly helps to dissipate lightning strikes. It helps to balance a system, because it is a good reference point of zero potential. But the Code states that the earth may not be used as the return path for grounding purposes.

    This is why “grounding” is not accomplished using only ground rods. A wire connection back to the grounded neutral is the main grounding system.

    This is also why neutrals and grounds are separated everywhere but at the main disco, because if they were connected, there would be multiple return paths for current, and high likelihood of electrocution from touching anything that is bonded in the structure.

    I hope I didn’t further confuse the issue.

    Delta

    I really appreciate that explanation. I knew what you were supposed to do but never exactly why. Thanks!

    Andrew

    A Working Pro since 1995!

    Member since March 26, 2014.

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