Equipment ground run questions

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  #1  
Old 12-18-12, 03:34 PM
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Equipment ground run questions

Hello all,

I have a couple of what are likely easy questions but I'm having trouble finding clarification. I am installing a standby generator with a service rated, 200A transfer switch. The transfer switch and breaker panel are in my garage on an exterior wall. It is all connected and I've had my first inspection. It went well with only a couple of issues to deal with. The one I have questions about is the equipment grounds. Because the transfer switch is service rated and my power now comes through it first, the breaker box is now a sub-panel. So, I have to move the main equipment ground and the earth ground to the transfer switch. The earth ground is a no-brainer as it's just the other side of the wall that the equipment is mounted on. The equipment ground however goes up into the attic then over toward the house and disappears in blown in insulation above the house. My water service comes in right next to that wall between the house and the garage, but the equipment ground is not connected to it where it is visible. From what I've read that is a no-no but it's a mute point anyway because the inspector said I could not splice the ground anyway, that I would have to do a new run. So, that said, I know where I'm going to run it to, to the water main coming in, and I know what size of wire I need, but I'm unsure about some generalities about the run itself. The house was built in '81 and the current run is not fastened down in the garage attic at all. So, my questions.

1. Do I need to fasten down the new run in the attic and if so, how often?
2. Anything I need to know about running it through the header or through the few studs it will need to go through?
3. I assume I also need a ground run from my transfer switch ground bar to the breaker panel ground bar? (and yes, the breaker panel neutral bar and ground bar are separate and the neutral is not bonded to the case any longer.)

Thanks in advance for any help you can provide!
John
 
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Old 12-18-12, 03:44 PM
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1. Do I need to fasten down the new run in the attic and if so, how often?
2. Anything I need to know about running it through the header or through the few studs it will need to go through?
If you're running 6 AWG solid bare copper, you can secure it with clips to the bottoms of the rafters - keeping it up and visible above the insulation.

If you're running stranded wire through holes drilled through the midpoint of each framing member, that's all the support it needs for the horizontal run.

3. I assume I also need a ground run from my transfer switch ground bar to the breaker panel ground bar?
Yes.

(and yes, the breaker panel neutral bar and ground bar are separate and the neutral is not bonded to the case any longer.)
Excellent!
 
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Old 12-18-12, 04:58 PM
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If you're running 6 AWG solid bare copper, you can secure it with clips to the bottoms of the rafters - keeping it up and visible above the insulation.

If you're running stranded wire through holes drilled through the midpoint of each framing member, that's all the support it needs for the horizontal run.
Thanks. I'm using 4 AWG solid bare copper as is the old run. The garage has no isulation and the old run including all of the house wiring is just laying across the ceiling studs and not secured, at least I didn't see anything securing it. It is not hanging from the rafters. Is it OK to lay the new run across the ceiling studs and maybe secure it with cable staples?

The run through studs will only be down by the water main. I'm dropping it down two studs away from the water main pipe because of permanent shelving in the way of a straight down drop. Is it OK to just run through the center of those two studs?

Thanks again,
John
 
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Old 12-18-12, 05:45 PM
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Is it OK to lay the new run across the ceiling studs and maybe secure it with cable staples?
Yep.

The run through studs will only be down by the water main... Is it OK to just run through the center of those two studs?
Sure. That won't impact its conductivity nor the framing strength.
 
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Old 12-18-12, 07:38 PM
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Thanks again! FYI, wasn't really worried about the stud integrity or the ground resistance, just about the code. I want the next inspection to be the last on this project.

John
 
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Old 12-18-12, 09:22 PM
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wasn't really worried about the stud integrity or the ground resistance,
I didn't think you were - or wondered why you might be. I only mentioned them because that's all I could imagine that one might be concerned about.
 
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Old 12-18-12, 09:39 PM
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Hehe, my problem is I don't have a code book and really don't want to buy one for the little use I would get out of it. I've just found that there are little things I wouldn't have thought would be in the code and didn't want to miss one on this part and end up with a third inspection needed. Thanks again for your help!
John
 
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Old 12-19-12, 06:32 AM
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Don't forget to jumper across the water meter and water heater too!

I'd also use this as a good opportunity to ensure your incoming telephone and cable TV is appropriately bonded (grounded). It's usually not something an inspector will check, but it's good to do and it's rare that the telco/catv installer did a decent job at it.
 
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Old 12-19-12, 07:32 AM
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Thanks for the tips! I understand the reason why I should jumper across the water meter & heater, but I'm curious about it. With the pipe being normally full of water and water being a good conductor, is there really a need for concern that rubber seals might stop the return path?

Thanks,
John
 
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Old 12-19-12, 09:29 AM
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With the pipe being normally full of water and water being a good conductor
A common misconception, Pure water is actually a good insulator. Impurities in the water supply the conductivity.
 
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Old 12-19-12, 09:53 AM
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Pure water is actually a good insulator. Impurities in the water supply the conductivity.
Interesting. I had always accepted what I was told about water being highly conductive but never investigated it myself. After your post I stuck my ohm meter leads in some bottled water. It didn't even measure any continuity until the 20 Meg scale. I then stuck them in my fish tank a got a reading varying between around 80K up to 150K. I learn something new every day if I'm paying attention. ;-)

Thanks again,
John
 
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Old 12-19-12, 06:40 PM
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I'd also use this as a good opportunity to ensure your incoming telephone and cable TV is appropriately bonded (grounded). It's usually not something an inspector will check, but it's good to do and it's rare that the telco/catv installer did a decent job at it.
An intersystem bond is a 2008 NEC requirement. This is the type I like.

http://www.platt.com/CutSheets/Arlin...5-CutSheet.pdf
 
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Old 12-19-12, 07:05 PM
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With the pipe being normally full of water and water being a good conductor, is there really a need for concern that rubber seals might stop the return path?
My understanding is that the jumper is also there for if/when the meter is removed. Occasionally, meters need to be replaced or recalibrated. When they are disconnected, if there is an electrical fault in the house (or sometimes even in another house), the jumper will ensure the two now disconnected pipes are at the same potential and the installer won't get shocked.
 
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Old 01-01-13, 11:11 PM
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I just wanted to come back and say thanks again to all of you. I got the job finished and passed the inspection so I'm a happy camper. Happy New Year!

John
 
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Old 01-02-13, 05:00 AM
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Congrats and thanks for the feedback.
 
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