[TowerTalk] Grounding Multiple Buildings

[Jim Brown]

This afternoon, I pulled out my 2002 copy of NEC and found the section 
applicable to what we have been discussing. I suggest that those who 
rail at my stupidity and tell me how wrong I am do the same. It is 
chapter 250.32.  Exhibit 250.16 applies directly to my installation, and 
shows only phase and neutral run between buildings, with neutral bonded 
in both buildings.

Poking around for a while with google, I learned that 250.32 was, 
indeed, changed in the 2011 edition to require that the ground conductor 
be carried between buildings, but installations like the one I described 
are specifically permitted provided that they comply with previous 
editions of the Code. The 2014 edition of the code spells out that 
exception in greater detail.

Here's the relevant section of the 2014 NEC.  When reading it, remember 
that "the grounded conductor" and "the grounded circuit conductor" refer 
to the Neutral, and "the Equipment Grounding Conductor" is "the green 
wire."

=   =   =   =   =   =


    250.32Buildings or Structures Supplied by a Feeder(s) or Branch
    Circuit(s).


      (A)Grounding Electrode.

Building(s) or structure(s) supplied by feeder(s) or branch circuit(s) 
shall have a grounding electrode or grounding electrode system installed 
in accordance withPart III of Article 250 
<https://www.inkling.com/read/national-electrical-code-2014-fire-protection-association/chapter-2/iii--grounding-electrode-system#0cea2eaa64664fc8b71aa9edb947622a>. 
The grounding electrode conductor(s) shall be connected in accordance 
with250.32(B) 
<https://www.inkling.com/read/national-electrical-code-2014-fire-protection-association/chapter-2/ii--system-grounding#15e3af26e92e4c9e9a46b550b86d2c34>or(C) 
<https://www.inkling.com/read/national-electrical-code-2014-fire-protection-association/chapter-2/ii--system-grounding#a17b15ce47544c399d6ac94585a70de6>. 
Where there is no existing grounding electrode, the grounding 
electrode(s) required in250.50 
<https://www.inkling.com/read/national-electrical-code-2014-fire-protection-association/chapter-2/iii--grounding-electrode-system#715ca3f2213743d8b1c39e012350acf5>shall 
be installed.

/Exception: A grounding electrode shall not be required where only a 
single branch circuit, including a multiwire branch circuit, supplies 
the building or structure and the branch circuit includes an equipment 
grounding conductor for grounding the normally non—current-carrying 
metal parts of equipment./


      (B)Grounded Systems.


        (1)Supplied by a Feeder or Branch Circuit.

An equipment grounding conductor, as described in250.118 
<https://www.inkling.com/read/national-electrical-code-2014-fire-protection-association/chapter-2/vi--equipment-grounding-and#4160cdae62a442cd9b30baba0a99655c>, 
shall be run with the supply conductors and be connected to the building 
or structure disconnecting means and to the grounding electrode(s). The 
equipment grounding conductor shall be used for grounding or bonding of 
equipment, structures, or frames required to be grounded or bonded. The 
equipment grounding conductor shall be sized in accordance with250.122 
<https://www.inkling.com/read/national-electrical-code-2014-fire-protection-association/chapter-2/vi--equipment-grounding-and#e247a77a0d734de5b340f8f0c4b1ba74>. 
Any installed grounded conductor shall not be connected to the equipment 
grounding conductor or to the grounding electrode(s).

/ExceptionNo. 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 of the feeder(s)./

/If the grounded conductor is used for grounding in accordance with the 
provision of this exception, the size of the grounded conductor shall 
not be smaller than the larger of either of the following:/

1./That required by220.61 
<https://www.inkling.com/read/national-electrical-code-2014-fire-protection-association/chapter-2/iii--feeder-and-service-load#26da8323c5794538a81f4571c94b261d>/

2./That required by250.122 
<https://www.inkling.com/read/national-electrical-code-2014-fire-protection-association/chapter-2/vi--equipment-grounding-and#e247a77a0d734de5b340f8f0c4b1ba74>/

/Exception No. 2:////If system bonding jumpers are installed in 
accordance with////250.30(A)(1) 
<https://www.inkling.com/read/national-electrical-code-2014-fire-protection-association/chapter-2/ii--system-grounding#0ced4916402044edbe29319bf4f95a2b>, 
Exception No. 2, the feeder grounded circuit conductor at the building 
or structure served shall be connected to the equipment grounding 
conductors, grounding electrode conductor, and the enclosure for the 
first disconnecting means./^^ //


Bottom line -- what I did in my buildings was according to Code in 2010 
when I did it, and the installation is "grandfathered" by the 2011 and 
2014 Codes. But it is not permitted now.

73, Jim K9YC