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I found this forum while settling a dispute with a co-worker about bonding neutrals and grounds here at our factory. It turns out I was correct, only bonding the two at the service disconnect. I decided to check my home to see if it was correct... I found the service disconnect bonded neutral to ground, then a 4-wire feed to the subpanel in the basement, and not bonded. So far so good. I also have a detached garage. The feed is a 3-wire. Two hots, and a neutral. The neutral and ground are NOT bonded in the panel in the detached garage, but the ground bar is connected to earth ground via a large bare copper wire and ground rod. But, there is NOT the 4th wire (ground wire) connecting this box to the property disconnect at the house. In this case, should this panel in the detached garage be bonded (neut to ground), should it be left as is, or is it imperitive that I run that 4th wire for the ground. Please reply, and thanks, Mike
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One last question.. If I have to now run a separate ground, can I run it direct burial separate from the other feeds, so I don't have to rip up my paved driveway?? Thanks Mike -
The following quotes are per this link
Scroll to this section towards the bottom of the page:
PICTORIAL EXAMPLE OF A GARAGE PANEL WITH 3 OR MORE CIRCUITS 240 VOLT 60 AMP, 100 AMP, 200 AMP BRANCH CIRCUIT WITH UNDERGROUND CONDUCTORS WITHOUT AN EQUIPMENT GROUNDING CONDUCTOR RAN WITH THE FEEDER SUPPLYING THE DETACHED STRUCTURE
It states the following:
When the detached garage main panel is supplied by a feeder that has no equipment grounding conductor ran with that feeder, from the main structure {usually dwelling} to the detached garage, then the neutral bar, and equipment grounding bar must be joined or married together as one entity, usually by a jumper bar attached between the two bars or by a jumper bar connecting the neutral bar to the metal of that panel box and the grounding bar bolted directly to that metal of that panel box. Article 250-32-B-2 & 250-102-E The neutral bar must married or joined together with the metal of the panel box and also the equipment grounding bar. Article 250-32-B-2
REMEMBER THAT IF A NON CURRENT CARRYING METAL PATH EXISTS BETWEEN THE TWO BUILDINGS CONNECTING THE TWO BUILDINGS, THEN YOU MUST INSTALL AN EQUIPMENT GROUNDING CONDUCTOR WITH THE FEEDER INSTALLED, SERVING THAT SECOND BUILDING FROM THAT MAIN BUILDING.
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Very helpful link!! Thank you!! So, I am okay just the way I am, as long as I bond the neutral and ground in the panel in the detached garage. I don't have a water pipe or the like between the two. HOWEVER, I do have a multi-pair phone wire between the two, so I therefore have a telephone in the detached garage, and I also can contol the garage door openers on that detached garage from the house via the unused pairs of that phone cable. So, does that therefore satisfy the condition of needing the separate ground feeder? And it also appears that if so, that ground feeder NEEDS to be with the other feeders. If this is all correct, then I have two choices: Completely remove that phone cable, or tear up my driveway and install the ground feeder. I hate the previous owner of this property!! Please reply!, and thanks! MikeComment
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No, doesn't look like either. NEC 250.32(B)(2)(2) says
there are no continuous metallic paths [u]bonded to the grounding system in both buildings or structures involved</u>
Your phone line is not bonded to the grounding system in your detached garage, so I think you have nothing to worry about.
I think the intent is to prevent anything like water pipes, air lines, etc. from carrying fault current back to the main panel from the outbuilding.
Please correct me if I'm wrong, but I think he is fine.
Now, In my case, I am confused whether or not I HAVE TO run a 4th wire EGC out to our barn. I can read into 250.32(B)(1) one way, and 250.32(B)(2) the other.
What gives?
Thanks,
~Jonathon Reinhart
~Jonathon ReinhartComment
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