Detached garage panel ground bar

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  #1  
Old 07-21-05, 09:38 AM
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Detached garage panel ground bar

I have the ground rod installed. Inside the panel there is a bar that is held away from the metal by plastic insulator mounts, I'm assuming this is for "common".
In my mobile home panel there are 2 bars one with all the whites connected, also insulated and one directly mounted to the metal with all the grounds connected. Can I add a second bar directly to the box for the grounds in the garage panel, and wire it up like is is in my trailer?

Oops sorry should have started a new thread.
 
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  #2  
Old 07-21-05, 12:36 PM
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I dont believe you drive a ground rod on detached buildings served from the main panel on a mobile home. Maybe some has that info from the code book??
 
  #3  
Old 07-21-05, 11:26 PM
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Well, actually I ran 100 amp sevice to the workshop from the pedestal.
I was told to drive a ground rod so I did. I just don't understand the bars. In the panel of the house they are seperate. One insulated for the white (Neutral or common) and one metal to metal for the green (ground). That's how I planned to do the garage as well, now I seem to be hearing that the grounds and commons can all be on the same bar?
 
  #4  
Old 07-22-05, 01:31 AM
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Not sure on this one but if that is a 4 wire feed to the workshop you have the egc playing neutral in the event the neutral opens. Plus I'm just not seeing the logic. The trailer panel is seperated ground and neutral bars and no ground rod, why the heck would you bond the neutral and gound at the workshop panel and drive a ground rod??? I cant seem to find a cut and dry answer in the NEC maybe someone can find the appropriate code reference??
 
  #5  
Old 07-22-05, 06:12 AM
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OK,

I have been away a bit due to some family illness but I will try to assist here a little.

1.) On a detached building ( ie: garage ) if you have more than (1) branch circuit within the detached building you will need a grounding electrode at the detached building.

Refer to Art 250-32 of the NEC and make note to the exception which refers to lets say if you run a single 120V ( nominal ) to the building and it has only (1) circuit inside it with is simply a branch circuit from the main panel source at a different location.

2.) The reason for the ground rod at the second location is to determine a ground potential at the remote location since it can be different than that of the supply EGC location.

I would go into more details but lets just say if you have a panel in the detached garage...you will need a ground rod.....refer to the article above and also take a gander at Art 250-32(b)(1) as well.

If you feel it is Cryptic......let me know and I will elaborate or I am sure Rac or John can also elaborate.....just remember you are right the common or neutral needs to float and not be bonded to the box....as well it needs to be insulated.....

You can add another ground bar if you wish or the one in it is full.....just mount it to the back metal cabinet......and by no means connect it in any way to the "floating" netural bar....and you are fine.....
 
  #6  
Old 07-22-05, 07:08 AM
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Originally Posted by ElectricalMan
OK, I have been away a bit due to some family illness but I will try to assist here a little.
I hope things turned out for the better.
 
  #7  
Old 07-22-05, 08:02 AM
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I see we were so worried about the ground rod requirements that we never did answer your questions. You can purchase a ground bar kit for the panel and install it in the predrilled swaged holes. You would not install the neutrals and grounds on the same bar. The bars must not be bonded together. I reviewed my counties requirements for grounding at mobile homes. They show a ground rod being driven at the service pedestal but no ground rod for the mobile home main panel.....only the egc in the power supply cord from the pedestal to the panel in the mobile home. Since this is a feeder not ran from the main panel in the mobile home but from the pedestal where the service equipment is located to the workshop I would agree that a ground rod should be driven.
 
  #8  
Old 07-22-05, 10:00 AM
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Remember,, the pedestal is the main entrance, the mobile home is a subfeed just like a detatched building, it is fed with 4 wires and the N and G are seperated just like the new panel in the garage should be.
 
  #9  
Old 07-22-05, 11:18 AM
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Roger,

I thought we did answer that question...but the ground rod was also a new part to the actual question....to use or not to use so that was important to elaborate on.

and by no means connect it in any way to the "floating" netural bar
Bascially he needs to keep the neutral bar floating and not bonded to the actual panel......but he can surly add another ground bar to the actual panel......
 
  #10  
Old 07-22-05, 03:04 PM
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Yep, looks like I need to get some eyeglasses Ya know we've been working long hours and its like 96F with heat index in the hundreds....I'm starting to think that a good nites sleep is in order. It gets a little embarassing to overlook something that obvious.....
 

Last edited by Roger; 07-22-05 at 04:26 PM.
  #11  
Old 07-22-05, 04:19 PM
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Rog,

Tell me about it....99 degrees today in VA.....VA i tell you.....not used to it being this hot here.....you know what heat can do to the brain....thehehe
 
  #12  
Old 07-22-05, 09:51 PM
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Thanks, I got it.

Careful in that heat and high humidity guys, it will kill ya.

I'm in Southern AZ, It was over 110 last week. Tommorrow it will be a record 40 straight days of 100 or more degrees. I know, it's a dry heat, just like my oven.

This week the summer rains started. Now it's not even dry anymore.

But hey, summer only lasts for six months here, then it goes back to being just hot.

Keep sucking that water bottle!!
 
  #13  
Old 07-23-05, 11:50 AM
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I can't imagine heat like that. stay cool and becareful as that is way to hot.
 
  #14  
Old 07-23-05, 06:52 PM
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Is it a three or four wire feeder?

Originally Posted by cimmaronjim
Well, actually I ran 100 amp sevice to the workshop from the pedestal.
I was told to drive a ground rod so I did. I just don't understand the bars. In the panel of the house they are seperate. One insulated for the white (Neutral or common) and one metal to metal for the green (ground). That's how I planned to do the garage as well, now I seem to be hearing that the grounds and commons can all be on the same bar?
Is the feeder to your shop three or four wires? The answer to that question is critical.

If the ground at the shop consist of only one ground rod then it must be tested to demonstrate a resistance to ground of 25 ohms or less. if it test higher or testing is impractical then you must drive a second rod at least six feet away from the first. In Arizona driven rods will usually not mesure less than a hundred ohms to ground. Since your shop is already built it is toolate to use any of the less expensive means of obtaining a low impedance ground so the best you can do is to install a second rod.

I hope that helps.
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  #15  
Old 07-23-05, 10:34 PM
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Really? The feeder is 4 wires. 8 foot ground rod. How would I measure resistance? I can't get an ohmeter to the buried end of the rod. If I installed a second ground rod would I tie the two together and then to the ground bar in the box or two seperate leads to the bar?

Oh, we just missed beating the record of consecutive 100 degree days. tied the old record of 39 yesterday.
 
  #16  
Old 07-24-05, 05:36 AM
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Yep the (1) or (2) ground rod debate will live on I am sure. The AHJ can simply demand (2) ground rods to be sure as they do around here but it is up to you to show them it is 25 or less and they do make a meters to read this but in the end......we found it easier to just drive the 2nd rod and be done with it.

That is something you will need to call your local building inspectors down at your AHJ and ask them. If they prefer (1) or (2) ground rods in the absence of other grounding methods. They will have no problem telling you I am sure as they have a standard each AHJ likes in a certain area.

ON reading the OHMS.....we have found a nice cheap unit that can do it if anyone out thier is DEAD SET on bucking your local AHJ when they tell you to drive (2) rods...in the long run if the AHJ says you have to do (2) or show him (1) is 25 or less.......go for the (2) and make them happy as a happy inspector is your BEST friend when a job needs a CO release.

BTW.......4 Wire or 3 Wire...if the garage is detached you would still need the ground rod ( unless other grounds are availble..UFER and so on )

Also to answer the last question, you will not run different lines back from each ground rod in the event you run (2)...they must be bonded to gether and come in as (1). Now it can be one long piece of ( # 6 CU Bare ) running to the first one and threw the acorn clamp and then along the ground down a few inches to the second groud rod acorn clamp in one solid run.

However, if you already ran the first one many AHJ will simply let you put another acorn on the first one you ran and then run a piece of # 6 CU Bare between the first rod and the second rod. Now some will say it needs to be one coninuous piece and others will say as long as they are bonded and they FIRST run is not cut and continuous....what I have found at many seminars with AHJ inspectors is...they only care they are bonded together correctly.
 
  #17  
Old 07-24-05, 08:15 AM
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Thanks guys, a second rod is easy enough to do.

BTW, E-man, The extreme heat here is usually accompanied by almost no humidity. Most think it is more comfortable than the kind of heat you get back east, to a point. Several days of 105 or more and no one continues to extoll the virtues of "dry heat." We have heat related deaths every year.
I think it is the duration of this hot weather that really wears you down. We have had years with temps approaching or exceeding 100 from late March through mid October. Our record high is 117, and this isn't even the hottest place in Arizona.

I've never lived any where where it gets real cold. I'd probably complain about that too.
 
  #18  
Old 07-24-05, 12:10 PM
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Originally Posted by cimmaronjim
Really? The feeder is 4 wires. 8 foot ground rod. How would I measure resistance? I can't get an ohmeter to the buried end of the rod. If I installed a second ground rod would I tie the two together and then to the ground bar in the box or two seperate leads to the bar?

Oh, we just missed beating the record of consecutive 100 degree days. tied the old record of 39 yesterday.
Since you ran a four wire feeder you should wire the shop exactly the same as your manufactured home is wired. You will have one buss bar for equipment grounding conductors and a separate one for the grounded current carying conductors (neutrals). Make sure that the panels neutral buss bar does not have a bonding strap or screw that is installed in the neutral buss to bond it to the panel boards cabinet. If there is a green screw or metal stap installed between the neutral buss and the cabinet then you should remove it.

What brand and model number of panel did you use in your new shop?

The ground rods are connected to the bonded EGC buss bar and not to the neutral buss.

I hope that helps
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Tom Horne
 
  #19  
Old 07-24-05, 03:11 PM
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Yep, I like it when people say...but its dry heat....HOT is HOT.

Also I figured I would mention also that since it is SOOO dry out west it can be a great bonus to have (2) ground rods ( UFER would be best in DRY areas because the concrete retains the moisture in the ground better)

yeah........chances are they will say Give me 25 OHMS or less and prove it...so as the code says...you can just add a second rod and be done with it.
 
  #20  
Old 07-24-05, 03:30 PM
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About the only way you can get 25 is if it is sitting in standing water,,, or at least wet soil, that ist goint happen out there, 2 or more rods but it seems I recall only ever seeing one rod on detached structures???????, 2 on service though.
 
  #21  
Old 07-24-05, 04:16 PM
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Well if you believe Rex Caldwells new book you drive 8 rods at the service equipment and 4 at detached buildings. That is the "above code" method anyway.
 
  #22  
Old 07-24-05, 09:33 PM
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"What brand and model number of panel did you use in your new shop?"
Cutler Hammer BR816L125RP

This is an all steel building bolted to concrete foundation, if that has any bearing.
 
  #23  
Old 07-24-05, 10:23 PM
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In my case I have a footing on a loading dock that sits in ground water and I drove a rod down from there and welded it to the building steel thru the rods in the footer. There are also rods at service entrance, I know they are not all in the same location but they are all bonded together. You really should have had a conductor in the footer of this building. But you dont so rods or a ring is what you have to deal with now and you need to bond this panel to the building steel, I would think a number 4 for 100A service. (someone will correct this I am sure) Its been a while and I forget the rules pertaining to steel blds.
 
  #24  
Old 07-28-05, 06:49 AM
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Allright, here is what I will do. I will install a ground buss bar, metal to metal in the panel. The panel itself is mounted (bonded) directly to the wall of the steel building.
I will drive a second 8 foot ground rod, run the ground wire from that through the first into the panel to the bar. The ground is pretty wet right now so driving should be easy enough.

This seems at least as good an installation as the original run to the mobile home which has already been signed off.

I can always make changes if it is deemed unsatisfactory.
 
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