Disconnect needed or not?

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ammklq143

Senior Member
Location
Iowa
Occupation
Electrician
On a service with a pole top disconnect (it's on a farm), do I need a grade level disconnect before I go underground to a new home, or is that just for an agricultural building and I can go straight from pole top disconnect, underground, and into the breaker panel in the house?
 

ammklq143

Senior Member
Location
Iowa
Occupation
Electrician
Is this before the meter or after? E.g who owns the pole-top disconnect?[/QUOTE

It's a CT meter installation and the CT's are before the disc. The CT's are the last utility point and the disc. is customer owned.
 

copper chopper

Senior Member
Location
wisconsin
its double pole because its 240 volt, also this provides no protection to any building however if you tap of of this and its not rated for this it would be incorrect. we dont know the distances from the pole to whatever building this is servicing but you should just come from that buildings panel and run to another building if that is the application we are trying to achieve.
 

ammklq143

Senior Member
Location
Iowa
Occupation
Electrician
Maybe this will help. It's not that difficult of a situation, so here's the details of the installation. It's an existing agricultural set up with an existing residential dwelling. The utility comes in to a xfmr pole and from there they run triplex to a meter pole. At the meter pole, the utility goes through a CT (last utility point) and into the pole top disconnect switch. It doesn't matter if it's double throw or not. It's a disconnect and it's owned by the member. On the load side of the pole top disconnect, the existing house and all shed are fed with overhead conductors. Now, they are eliminating the existing dwelling and bringing in a manufactured home. I am going from the load side of the existing pole top disconnect, down the pole, underground to the breaker panel in the new home. My question was, is it necessary to put a grade level disconnect at the bottom of the pole before going underground to the house, or is the pole top disconnect sufficient?

I was thinking that you didn't need a grade level disconnect at the bottom of the pole, beneath the pole top disconnect as long as it wasn't feeding an agricultural building, so in this case, there is a disconnect at the top of the pole and it's feeding a dwelling and a grade level wouldn't be necessary.
 
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Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
You need a disconnect at the home so I don't know why you would need one at the pole. Service equipment should be readily accessible however I am not sure if there is an exemption for agriculture. I have heard of this before.

Two things to watch. Once you leave the disco at the pole you will need an egc run with your conductors as they are feeders. You also cannot enter a home with USE wire unless it is dual rated such as Xhhw or something similar. Art. 225 comes into play here esp. Part II
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
Is the disconnect on the pole a site isolating device? I have no idea what that is but I see 547.9 allows that to not be readily accessible-- 547.9(A)(8)
 

north star

Senior Member
Location
inside Area 51
* * *

The disconnecting means to the manufactured home will require a "readily accessible"
disconnect, at / near the point of entry into the structure. - - See Article 550.11(A),
`08 NEC.


* * *
 

ammklq143

Senior Member
Location
Iowa
Occupation
Electrician
Thanks for the input from everyone. I was pretty sure I was correct on this, but I called the inspector and the inspector supervisor just to be sure. The code does not require a grade level disconnect for this installation, nor does it require an EGC to be run with the conducutors. If it were supplying an agricultural building that housed livestock, it would need a grade level disconnect with overcurrent protection. Since it's a residential dwelling the conductors can run straight from the pole top disc. and go underground directly to the breaker panel in the house without an EGC. 2 ground rods at the service pole and an UFER ground in the house. FYI. One thing I do remember from a previous installation like this is that it does need marking tape in the trench if there's no EGC. That's what the inspector told me anyway.
 
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resistance

Senior Member
Location
WA
Thanks for the input from everyone. I was pretty sure I was correct on this, but I called the inspector and the inspector supervisor just to be sure. The code does not require a grade level disconnect for this installation, nor does it require an EGC to be run with the conducutors. If it were supplying an agricultural building that housed livestock, it would need a grade level disconnect with overcurrent protection. Since it's a residential dwelling the conductors can run straight from the pole top disc. and go underground directly to the breaker panel in the house without an EGC. 2 ground rods at the service pole and an UFER ground in the house. FYI. One thing I do remember from a previous installation like this is that it does need marking tape in the trench if there's no EGC. That's what the inspector told me anyway.
Your inspector is correct, as I do this type of underground install on occasion, but in most cases the authority is the serving utility. I kept my mouth shut, because you mentioned agricultural building, not residential.
 

kwired

Electron manager
Location
NE Nebraska
From 547.2 definitions:

Site-Isolating Device. A disconnecting means installed at the distribution point for the purposes of isolation, system maintenance, emergency disconnection, or connection of optional standby systems.


This is only required when two or more art 547 buildings are supplied by same source.

A dwelling is not a 547 building but can be supplied by same source as a 547 building.

Apparently what we are using around here is now wrong if 2011 NEC applies. A 2011 change requires it to be not less than the height above grade required by 230.24 for the conductors it supplies. POCO has provided a disconnect of some sort for ever around here and are always readily accessible.

But small farms are disappearing. Most new buildings that fall under 547 are like small industrial plants and have much larger services ran directly to the building. Have a dairy farm I do work for that has a 800 amp 277/480 volt service. Big change from what they upgraded from that only had a 200 amp 120/240 service. The one before that was probably only 60 amp 120/240.

But they are no longer milking just 25 cows or so more like 1000+
 
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