Connecting garage panel to main panel.

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Old 06-13-20, 09:01 AM
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Connecting garage panel to main panel.

Hello DIYers,

In previous posts I have asked and received great feedback regarding my plan to feed power from my house to a new garage that is going to be built. I would really appreciate the knowledgeable individuals review of the methods and materials I intend to use to perform this project. Any constructive thoughts by readers of this material would be welcome.

The panelboard in garage will be fed from 60-amp breaker in existing service panel and it will be rated at 100-amp (100-amp breaker will be used as disconnect in garage). I am providing photos of the service panel that the feeder cable will be exiting. A junction box will be mounted on the home's exterior brick wall and located basically right behind the service panel.

I plan to do the following:
  • Use 6/3 (with ground) NM-B wire exiting from the top of service panel and feed thru hole to be drilled in home's brick exterior.
  • 6/3 NM-B cable will enter into 6" x 6" x 4" PVC NEMA 4X enclosure thru a hole I will drill in back of enclosure that is mounted on the home's brick exterior
  • Will use Polaris Insul-Tap connectors to splice wires of the 6/3 NM-B cable to #6 THHN/THWN wire, and also splice #10 bare ground from the NM-B cable to a green #10 THHN/THWN wire.
  • Will run the #6 THHN/THWN wires, and the #10 THHN/THWN ground wire, into 1" PVC fed from hole drilled into bottom of NEMA 4X enclosure
  • 1" PVC will be buried so top of PVC is 18" below grade and will be fed to 90-degree PVC sweep fed into garage thru its rat wall
  • Will use Ufer method for ground electrode (plan on using 20 feet of #2 bare stranded conductor as grounding electrode)
Again, I would very appreciative if the knowledgeable individuals on this forum could review and comment on my plans. Thank you.



 
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Old 06-13-20, 09:28 AM
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I apologize for the misleading Thread Title of this post. I was originally going to ask about the feed from my home's service panel to the junction box mounted on the home's exterior, but then decided to just provide my whole plan. Forgot to change Thread Title after doing so.
 
  #3  
Old 06-13-20, 09:58 AM
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Can you do back to back LBs and skip the junction box?

large blue or gray wirenuts will work fine for 2 #6 instead of the Polaris.
 
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Old 06-13-20, 11:40 AM
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Hello pcboss,

Using LBs was my first thought, but because the top of the service panel has so many cables being fed into various knockout locations, it makes it difficult to find a good location to land the LB on top of the panel and also near an area of the wall in order for me to make an exit hole big enough for the 1" conduit to go thru. There are other cables in the area and they too are being fed through the wall. Need to make sure I keep proper distance between the holes in the wall. I will also need to expand the size of one of the unused 1/2" knockouts still available in the panel. If I go with the NM-B cable option the size of hole necessary in the panel to would not be as large as required to go with 1" LB option.

I had given thought to just going thru the side of the panel at the lower left side of it and mounting an LR conduit body, going up along the side of the panel to an LB that would go thru the wall and meet up with another LB. I really am not keen on having a 6"x 6" x 4" box mounted on the side of the house. Plus, I am not keen on having to do the splice operation either.

Should I decide to go with the idea of mounting a box to the exterior brick wall, is it acceptable to use NM-B to feed from the service panel, thru the wall, and then into the exterior-mounted box? The NEC seems to be a bit unclear about running NM-B cable through brick walls and what is considered a wet/damp location. Please know that I do intend to pull an electrical permit for this project.

Thank you for your comments, pcboss.
 

Last edited by Wolverine77; 06-13-20 at 12:51 PM.
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Old 06-13-20, 11:44 AM
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Title changed...................
 
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Old 06-13-20, 11:51 AM
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NM into the back of the box should be fine.
 
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Old 06-13-20, 12:50 PM
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Thank you, PJmax! I appreciate your changing the title of the thread.
 
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Old 06-13-20, 01:00 PM
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One other question. I need to go about 40 feet with the PVC as it travels from my house to the new garage, and this will require a bend in the PVC run at about the midway point between the house and the garage. Being that I am running a quantity of (3) #6 THHN wires, as well as a #10 THHN ground, do you think it will be okay using a 90-degree sweep for the bend or would it be necessary to bend the actual PVC in not so acute an angle? Thank you.
 
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Old 06-13-20, 09:10 PM
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A lesser angle will pull easier than a 90. Can you just do a sweeping bend in the conduit? Two 45s will also give you a 90 degree turn.
 
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Old 06-13-20, 09:15 PM
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Put the splice junction box inside and leave the box into the exterior LB.
 
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Old 06-13-20, 10:54 PM
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I am not a professional, so you absolutely should get expert advice and not just follow what I'm saying.
But I've heard that in installations like this, the subpanel should not have its own earth ground, but should rather be connected back to the ground at the main panel. Oof, or maybe its that the earth ground and "neutral" should not be bonded together at the subpanel. Ask someone who really knows :-)
 
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Old 06-14-20, 04:33 AM
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Hello pcboss,

I like your idea about using two 45-degree sweeps in order to achieve the 90-degree turn the PVC needs to have, while still maintaining a gentle arc leading to the garage. Thank you!
 
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Old 06-14-20, 04:39 AM
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Hello pcboss,

Sadly, I really don't have any good place to land a 6" x 6" x 4" splice box on the interior structure of my home, while still being able to maintain close proximity to the service panel. Too many existing cables being fed into service panel. There is a deck running along the exterior wall that will limit how far to the left of the service panel I could land the splice box, and there are cables running along this portion of the interior of the home.

 
  #14  
Old 06-14-20, 06:02 AM
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Correct: The subpanel does not need ground rod connection.
Correct: The subpanel must not have ground and neutral interconnected (bonded), grounding accomplished by the ground wire (equipment grounding conductor) in the feed back to the supra panel.

Experts do disagree about ground rods in different locations about the house. But they all do agree that all the various ground rods need to be interconnected using #6 copper wire
 
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Old 06-14-20, 08:38 AM
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Right now we are assuming that this is for a DETACHED garage. As such it will need a GEC so the UFER mentioned will suffice with no ground rods needed. If garage is attached to the house then ufer is not to be used.
 
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Old 06-14-20, 09:23 AM
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Agreed Astuff, and yes, this is a detached garage. The wires leaving my home's main service panel are considered part of a feeder and not a branch circuit, hence the need for a separate grounding electrode/ conductor. Branch Circuit is defined in Chapter 1 of the NEC book as, "The circuit conductors between the final overcurrent device protecting the circuit and the outlet(s)".

In this case the "...final overcurrent device protecting the circuit" would be in the panelboard that is located in the detached garage. The wires from the my home's main service panel feeding the panelboard in the detached garage are going to a 100-amp main breaker in the garage's panelboard, and this main breaker will serve as a disconnect means for the panelboard in the garage. Since there are individual breakers inside the garage's panel board, and they are what the garage's circuit conductors are connected to, these breakers are considered "...the final overcurrent device protecting the circuit and the outlet(s)".
 
  #17  
Old 06-14-20, 11:06 AM
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Since you are reviewing all details... Another limitation is that copper NM-B is only rated at 55 amps. Going to a 60 amp breaker is fine but only if the calculated load is 55 amperes or less.
 
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Old 06-14-20, 11:49 AM
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Hello Astuff,

Thank you for calling the amperage issue out with respect to 6/3 NM-B. The calculated load would be no more than 55 amps, but I will let my AHJ know about my intention of using of 6/3 NM-B as a feeder from the service panel to the junction box.

Thanks, again, for your comment.
 
  #19  
Old 06-25-20, 11:19 AM
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Question:

When running the Schedule 80 PVC from the junction box mounted on my home's exterior brick wall and then connecting it to the 90 degree Schedule 40 PVC that is going to be buried 18" underground, is it necessary to have the Schedule 80 PVC affixed flush to the brick wall and then secured to the wall with a strap or can the PVC be off the wall a small amount and then secure it with a clamp. I ask because I am not aware of any 1" PVC offset available which would make it easier to mount the PVC flush against the wall and then feed it into the junction box. Thank you.
 
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Old 09-09-20, 11:46 AM
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I just want to thank all of those who provided advice to me as I asked questions related to running electrical power to my detached garage. I passed both the rough and final electrical inspections without a hitch. Again, thank you to all who shared their electrical knowledge with me.
 
 

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