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Old 04-23-2019, 05:44 PM   #1
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Conduit Grounding


When I recently built my house I ran a 1 1/4 PVC conduit from panel to a 6 by 6 inch metal junction box in opposite wall at the level of receptacles. I ran # 10 wires from panel thru this box to a 220 receptacle to power a treadmill. I installed a short screw type grounding bar in box to ground the box using the ground for the 220 circuit as it passed thru to receptacle. The plan was to use this box and conduit to later run power to detached garage about 40 feet from house. I have now done this by running four #6 wires from panel thru the pvc conduit to previously mentioned 6 by 6 box then thru wall via a metal conduit down to ground level connecting to an underground pvc conduit to garage then up garage wall by metal conduit thru wall to secondary panel in garage. All inspected and in service for 1 year.
My question is about any further need to ground the metal conduit portions of the outside/under ground conduit. Metal down wall pvc underground then metal up garage wall. I asked inspector if I suhould have broken the #6 ground wire to ground the house end and at termination ground garage end but he said no need. Here is a photo of the house side as it exits the inside the wall 6 by 6 box. I just pulled the garage subpanel cover and it has a ground bushing grounding that part of the distal end of conduit. I had forgotten how I had wired that portion.
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Old 04-24-2019, 06:16 AM   #2
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Re: Conduit Grounding


Is your junction box still grounded from the original circuit you ran?
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Old 04-24-2019, 09:54 AM   #3
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Yes the ground is still there with #12 wire not # 10. I just took a photo. I have plenty of threads on metal conduit stub-can you buy a split grounding bushing? If so I could run a ground to grounding bar or even remove some insulation from garage ground wire and attach to split grounding bushing.
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Old 04-24-2019, 11:35 AM   #4
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Re: Conduit Grounding


I canít tell if the box is grounded. I see your ground block but I canít tell what is connected to it. If nothing then the box and exterior conduit is floating which isnít allowed. Can you post another picture showing the terminal block with wires pushed out if way?


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Old 04-24-2019, 12:57 PM   #5
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I wired the entire house and garage myself. I split the ground for the 220 treadmill and definitely attached it to the ground strip. I did it backwards for some reason. I ran the ground to the 220 receptacle and box and then back to the grounding strip. The receptacle is only about 1 foot away in a metal 4 by 4 box also. I used metal 4 by 4 boxes for entire house.
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Old 04-24-2019, 02:56 PM   #6
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I did some checking and you can buy a split screw on grounding bushing from several manufacturers. I think the best thing to do as I need a protective bushing anyway on the 1 1/4 inch rigid nipple is to install the split bushing and using a soldering iron remove about 1/2 inch length of insulation from the garage circuit ground to go into the split grounding bushing without having to cut the ground wire. Would this approach be a good idea? I could even put a second ground wire from this bushing connection down to the ground bar for the 6 by 6 box even though it is already grounded by the 220 receptacle ground.
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Old 04-24-2019, 04:44 PM   #7
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Re: Conduit Grounding


If you would cut the #10 cu grounding wire and terminate both ends on the ground bar, that's your easiest fix. That way you could pigtail a #10 to the grounding bushing you are adding to the nipple, and still have the receptacle grounded. #10 copper is good for equipment grounding up to 60 amps, and much easier to work with than the #6. The #12 ground you currently have is undersized for the garage feeder
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Old 04-24-2019, 05:03 PM   #8
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I was wrong about the #10. The whole 220 circuit to treadmill is #12 on a 20 amp double breaker. The garage is on a 50 amp breaker and the garage ground is one size smaller than the #6 main conductors. The ground is #8. I have plenty of length to cut it and attach both ends to ground bar then run another #8 from new bushing to bar also. Would that be a reasonable solution?
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Old 04-24-2019, 06:30 PM   #9
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Re: Conduit Grounding


Yes that would work
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Old 05-02-2019, 09:20 AM   #10
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I have fixed the problem using a split grounding bushing. I cut the #6 ground wire to garage and reconnected using the ground bar then run a # 8 bare copper from new grounding bushing to ground bar. Will try to post photos.
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