Another Sub-Panel Nightmare


  #1  
Old 04-09-12, 05:20 PM
littlefin's Avatar
Member
Thread Starter
Join Date: Apr 2012
Posts: 7
Upvotes: 0
Received 0 Upvotes on 0 Posts
Another Sub-Panel Nightmare

I replaced an old screw-in-fuse box with a new sub-panel that has a main breaker in it. The box below the meter on the power pole has two 50Amp breakers in it. One for the Mobile Home, and one for the Garage.

The three cables that run from the box on the pole, to the garage are 4Ga insulated, there underground, about 150 feet long.

Two Hots, and One Neutral. (No ground)

In the new sub-panel I ran the Neutral/Return & the Bare Ground on the same bus bar like you would in a Main Supply. I know that it's not 1950 anymore, and that,s not the way it should be:NO NO NO:

Should I isolate the Bare ground wires on a separate bar and run that to a grounding pole outside? Or do I just leave it like it is?

I really don't want to dig 150 feet ( some of it under the trailer home ) to install a fourth wire to ground it.

Why do I always end up with these kind of jobs?
 
  #2  
Old 04-09-12, 06:52 PM
ray2047's Avatar
Member
Join Date: Mar 2006
Location: USA
Posts: 29,711
Upvotes: 0
Received 15 Upvotes on 13 Posts
For safety and current code you should run four wires, two hots, one neutral, one ground. The neutral should be isolated from the box and a ground bar bonded to the box added.
 
  #3  
Old 04-09-12, 07:01 PM
littlefin's Avatar
Member
Thread Starter
Join Date: Apr 2012
Posts: 7
Upvotes: 0
Received 0 Upvotes on 0 Posts
Ray, Thanks for the reply.

Wouldn't a grounding pole in the earth work as a ground for the box ,and the bare ground wires?
 
  #4  
Old 04-09-12, 07:39 PM
pcboss's Avatar
Forum Topic Moderator
Join Date: Jul 2002
Location: Maryland
Posts: 13,976
Received 194 Upvotes on 170 Posts
Mobile homes have needed a 4 wire feeder as long as I can remember.

Are the conductors in conduit?
 
  #5  
Old 04-09-12, 07:45 PM
SeaOn's Avatar
Member
Join Date: Dec 2011
Location: USA
Posts: 302
Upvotes: 0
Received 0 Upvotes on 0 Posts
Mobile Homes are under a different set of rules. I believe the rules are under the 2005NEC (Federal code applies under 2005NEC—superseding any current NEC). So: 550.33(A)(2) Exception: For an existing feeder that is installed between
the service equipment and a disconnecting means as covered
in 550.32(A), it shall be permitted to omit the equipment
grounding conductor where the grounded circuit conductor
is grounded at the disconnecting means in
accordance with 250.32(B) Exception.

Even then, it is best to check with your jurisdiction.

Just my .001.
 
  #6  
Old 04-09-12, 08:28 PM
littlefin's Avatar
Member
Thread Starter
Join Date: Apr 2012
Posts: 7
Upvotes: 0
Received 0 Upvotes on 0 Posts
Pc boss,

The sub-panel is going to the garage not the mobile home. No the wires are not in conduit. They are buried under ground. I wish they would have used conduit, that would have made running a ground possible.
 
  #7  
Old 04-09-12, 08:51 PM
littlefin's Avatar
Member
Thread Starter
Join Date: Apr 2012
Posts: 7
Upvotes: 0
Received 0 Upvotes on 0 Posts
Here'a a drawing of it.
 
  #8  
Old 04-09-12, 09:29 PM
SeaOn's Avatar
Member
Join Date: Dec 2011
Location: USA
Posts: 302
Upvotes: 0
Received 0 Upvotes on 0 Posts
If the existing install was installed without an equipment grounding conductor, then I believe your install will fall under NEC 250.32(B) ex.. Which allows you to connect a grounded conductor to the buildings disconnecting means and to the grounding electrode or electrodes, and shall be used for grounding or bonding of equipment, structures, or frames required to be grounded or bonded. But, the existing install must meet the requirements of the three (3) exceptions+: a. No equipment grounding conductor was ran with the supply conductors. b. There are no continuos metallic paths bonded to the grounding system in each structure involved. c. Ground fault Protection of equipment has not been installed on the supply side of the feeder. Where the grounded conductor is used and meets the provisions of the exception, the grounded conductor shall not be smaller than the larger of the two: 1. That required by 220.61/ 2. That required by 250.122. Definition of structure: That which is built or constructed. I believe we can define your pole as a structure per code. Also: If you don’t have a grounding electrode system serving the detached garage, then you must install a new grounding electrode system as described in NEC 250.50. If you don’t have anything available per the above article, then you may use a made electrode per NEC 250.52. If available, all of those grounding electrode sources listed must be connected together to make the grounding electrode system.
 

Last edited by SeaOn; 04-09-12 at 10:16 PM.
  #9  
Old 04-10-12, 05:50 AM
pcboss's Avatar
Forum Topic Moderator
Join Date: Jul 2002
Location: Maryland
Posts: 13,976
Received 194 Upvotes on 170 Posts
As long as there are no other metallic paths between the garage and the pole you were allowed to use a 3 wire feeder and rebond the neutrals and grounds just like a service.

You will need grounding electrodes at the garage.
 
  #10  
Old 04-10-12, 02:26 PM
littlefin's Avatar
Member
Thread Starter
Join Date: Apr 2012
Posts: 7
Upvotes: 0
Received 0 Upvotes on 0 Posts
Thanks so much Seaon & PcBoss for all the information. I will leave it for now, but as soon as I can get some help I will run a ground conductor to the garage so I can finish it up correctly.

I really am glad that this forum is available. I had no one else to ask.

Thanks Again!
 
  #11  
Old 04-10-12, 07:14 PM
Tolyn Ironhand's Avatar
Group Moderator
Join Date: Nov 2007
Location: United States
Posts: 14,332
Received 877 Upvotes on 740 Posts
If this was installed under 2005 code it would have been up to code and would be grandfathered in.

If there is no water in the garage you would likely need two ground rods 6' apart. (Under 2005 code)
 
  #12  
Old 04-10-12, 08:07 PM
littlefin's Avatar
Member
Thread Starter
Join Date: Apr 2012
Posts: 7
Upvotes: 0
Received 0 Upvotes on 0 Posts
Ironhand , Thanks for the advise.
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: