Â* The old panel in my shop is giving up , the old aluminum buss bars
are just getting too bad to continue using it . So Thursday while we
were down in Memphis I picked up a new box - 20 slots/20 ckts/100 amp
in-feed breaker (also gets a 100A feed breaker in the main panel)Â* . It
has 2 neutral/ground connection strips , connected by a link at the
bottom and not bonded to the enclosure . I plan to move the ground strip
from the old box and use both of the ones in the new for neutrals .

Â* Here's where I'm not sure what I want to do - the supply from the
main panel in the house is 3 wire 2/0 aluminum . I'm not sure at this
point how I want to handle the neutral/ground issue . I'm inclined to
let the neutral float and drive a separate ground rod for the shop .
Ground will be bonded to the enclosure . I don't think that will give me
any ground loop issues , but there may be a problem with a difference in
potential between the ground and neutral . I guess I could just let the
neutral act as ground too , they are bonded in the main panel - oops ,
no they're not bonded in the main panel , the only place the neutral is
grounded is up on the pole at the transformer . Main panel ground is a
standard 8' ground rod and it's bonded to the enclosures (meter base
too) . The other issue I have is what to use to connect a copper pigtail
to the end of that 2/0 al wire . The al wire may be too large in
diameter for the in-feed breaker in the new panel .

Â* --

Â* Snag

On 12/9/17 4:45 PM, Terry Coombs wrote:
Â* The old panel in my shop is giving up , the old aluminum buss bars
are just getting too bad to continue using it . So Thursday while we
were down in Memphis I picked up a new box - 20 slots/20 ckts/100 amp
in-feed breaker (also gets a 100A feed breaker in the main panel)Â* . It
has 2 neutral/ground connection strips , connected by a link at the
bottom and not bonded to the enclosure . I plan to move the ground strip
from the old box and use both of the ones in the new for neutrals .

Â* Here's where I'm not sure what I want to do - the supply from the
main panel in the house is 3 wire 2/0 aluminum . I'm not sure at this
point how I want to handle the neutral/ground issue . I'm inclined to
let the neutral float and drive a separate ground rod for the shop .
Ground will be bonded to the enclosure . I don't think that will give me
any ground loop issues , but there may be a problem with a difference in
potential between the ground and neutral . I guess I could just let the
neutral act as ground too , they are bonded in the main panel - oops ,
no they're not bonded in the main panel , the only place the neutral is
grounded is up on the pole at the transformer . Main panel ground is a
standard 8' ground rod and it's bonded to the enclosures (meter base
too) . The other issue I have is what to use to connect a copper pigtail
to the end of that 2/0 al wire . The al wire may be too large in
diameter for the in-feed breaker in the new panel .

Â* --

Â* Snag

It's best to get the neutral and earth at the same potential
especially if you have
livestock. I bet you already know that. I've seen stories of animals
that won't drink or
cows that won't milk because of ground loops.
I like this pictu

https://www.bing.com/images/search?view=detailV2&ccid=dUIWgCvZ&id=FB485FA3F206 ECBA07A9C7C34BCCC4EE2FC41E8A&thid=OIP.dUIWgCvZFit3 kBa07xgd_AEsDh&mediaurl=http%3a%2f%2fwww.mikeholt. com%2fgraphics%2ftouch.gif&exph=480&expw=640&q=ear th+bonding+++mike+holt&simid=608016879678589222&se lectedIndex=1&ajaxhist=0

or http://alturl.com/5wr5f

There's a chart in this article showing typical earth resistance:
http://www.utilityproducts.com/articles/print/volume-16/issue-3/product-focus/safety-products/step-and-touch-potential-awareness.html

or http://tinyurl.com/y7zrbf5k

On Sat, 9 Dec 2017 16:45:37 -0600, Terry Coombs
wrote:

Â* The old panel in my shop is giving up , the old aluminum buss bars
are just getting too bad to continue using it . So Thursday while we
were down in Memphis I picked up a new box - 20 slots/20 ckts/100 amp
in-feed breaker (also gets a 100A feed breaker in the main panel)Â* . It
has 2 neutral/ground connection strips , connected by a link at the
bottom and not bonded to the enclosure . I plan to move the ground strip
from the old box and use both of the ones in the new for neutrals .

Â* Here's where I'm not sure what I want to do - the supply from the
main panel in the house is 3 wire 2/0 aluminum . I'm not sure at this
point how I want to handle the neutral/ground issue . I'm inclined to
let the neutral float and drive a separate ground rod for the shop .
Ground will be bonded to the enclosure . I don't think that will give me
any ground loop issues , but there may be a problem with a difference in
potential between the ground and neutral . I guess I could just let the
neutral act as ground too , they are bonded in the main panel - oops ,
no they're not bonded in the main panel , the only place the neutral is
grounded is up on the pole at the transformer . Main panel ground is a
standard 8' ground rod and it's bonded to the enclosures (meter base
too) . The other issue I have is what to use to connect a copper pigtail
to the end of that 2/0 al wire . The al wire may be too large in
diameter for the in-feed breaker in the new panel .

Â* --

Â* Snag

The answer is simple. If you only have an existing 3 wire feeder leave
the panel as it is, put the bonding jumper in (green screw or a strap)
and exploit the exception.
Drive a rod. That is still required in any configuration.
You can't just use a rod as your ground, it needs to be bonded to the
neutral somewhere. If you only have a 3 wire feeder that will be in
the sub panel.

250.32(B)(1)
Exception No.1: For installations made in compliance
with previous editions of this Code that permitted such connection,
the grounded conductor run with the supply to the
building or structure shall be permitted to serve as the
ground-fault return path if all of the following requirements
continue to be met:
( 1) An equipment grounding conductor is not run with the
supply to the building or structure.
(2) There are no continuous metallic paths bonded to the
grounding system in each building or structure involved.
(3) Ground-fault protection of equipment has not been installed
on the supply side ofthefeeder(s).
NATIONAL ELECTRICAL CODE 2014 Edition