Thread: Does the code allow this subpanel connection?

Here is my situation: I would like to add a new subpanel in a new detached garage. I have an existing detached horse stable located a hundred feet from the new garage and a few hundred feet from my house.

The service feed to the stable is currently through my basement in my house and is fed through a separate dedicated 200 amp breaker box in my house basement. (It does not go through my main house panel.) The line then goes underground to a junction box in my yard where there is a splice in the line, which was located there by the electrician because of a the long pull. It then feeds to the 200 amp panel in the stable. The system is only two years old.

I would like to know whether we can tap into the splice at the underground junction and have a new line added that runs to the new garage, whith its own subpanel. I likely only need a 60 amp or so subpanel. This would be the least disruptive way of addidng electical service to the new garage.

The question (I think is) is: Can you have a splice in an underground feeder line that goes to two different panels?

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Others will chime in, but it doesnt seem right, not so sure the first splice is even allowed.

how is the splice made? is it housed in a waterproof housing easily accessable? run in conduit?

That's probably fairly large conduit, large enough to run additional conductors for your 60 amp service to the garage. Another option may be to replace the junction box with a breaker panel feeding the 2 buildings.

I am guessing that the juction box is above ground and not buried. If that is the case...as long as you feed the new garage with 200 amp wire you should be okay making joints in the junction box.

Oh, I read it and assumed it was buried.

Originally Posted by Joe Suelter

Oh, I read it and assumed it was buried.

And you could be right...I was just guessing myself.

I probably used the wrong terminology in describing the existing box as a junction box. The line is an underground line, four very large individual conductors in a 3 inch conduit, which comes up to near the surface and is housed in a plastic enclosure (open to the ground below) which closes flush with the lawn. This is where I am suggesting the splice be made. I do not want it to come above ground as it is in the middle of my yard.

If we need to use the 200 amp wire, that would be fine.

Do this change any of your answers?

Originally Posted by David Latzko

I probably used the wrong terminology in describing the existing box as a junction box. The line is an underground line, four very large individual conductors in a 3 inch conduit, which comes up to near the surface and is housed in a plastic enclosure (open to the ground below) which closes flush with the lawn. This is where I am suggesting the splice be made. I do not want it to come above ground as it is in the middle of my yard.

If we need to use the 200 amp wire, that would be fine.

Do this change any of your answers?

What type of wire is in the conduit?

I can't say for sure, but these are four large wires with black insulation, and the disconnect and existing panel in the stable is 200 amps I recall hat they were aluminum conductors.

Originally Posted by David Latzko

I can't say for sure, but these are four large wires with black insulation, and the disconnect and existing panel in the stable is 200 amps I recall hat they were aluminum conductors.

Here is what the NEC says..you can do what you are wanting to do if you do it correctly.

300.5 Underground Installations.

(A) Minimum Cover Requirements.

Direct-buried cable

or conduit or other raceways shall be installed to meet the

minimum cover requirements of Table 300.5.

(B) Wet Locations.

The interior of enclosures or raceways

installed underground shall be considered to be a wet location.

Insulated conductors and cables installed in these enclosures

or raceways in underground installations shall be
listed for use in wet locations and shall comply with
310.8(C). Any connections or splices in an underground

installation shall be approved for wet locations.

I'm sure it would be cheaper to pull some #6 through the existing conduit rather than splice new 3/0 to the garage and have to put a 200 amp panel in the garage. Have you talked to an electrician about this?

The electrician will be coming out Monday to assess. The existing conduit is already tight with the existing wires.

How big is your junction box? To make the number of joints you are taking about and to make them watertight is going to take a large box.

100 feet of 10/3 NMW direct burial cable with a 30 amp breaker in the main panel will be a lot cheaper than what you are proposing. Just ask your sparky.

Getting to the existing main pain panel would require a bit of carpentry work and boring under under an access road. That work alone would likely cost about $2500. Unless you talking about a difference of that much, the 200 amp solution is likely cheaper.

But everyone here seems to be worrying about my dollars more than my original question, which was: Can you by code create an splice in a line (undergound) that feeds two different subpanels, and if so , what are the conditions? What I think I am hearing is that it is ok, so long as I use approved underground splicing methods, so long as the new line rated for 200 amps, and as long as the new panel is a 200 amp panel. I am hoping that is the correct summary. If there are more conditions , please comment and thank you all.

Originally Posted by David Latzko

The service feed to the stable is currently through my basement in my house and is fed through a separate dedicated 200 amp breaker box in my house basement. (It does not go through my main house panel.) The line then goes underground to a junction box in my yard where there is a splice in the line, which was located there by the electrician because of a the long pull. It then feeds to the 200 amp panel in the stable. The system is only two years old.

I am reading this as you have at least 2 power drops from the grid to your house. Is that correct? If not, how does the second panel get power if it doesn't go through your main panel?

Pictures of this underground splice might be helpful to get a better grasp on what is going on there.

2 years ago when the stable was added, the electrician called the power company and added a second entry line into my basement. So I have one meter ouside, but two main lines entering my house. The first line goes to the main panel for my house. The second new line does not go through the main house panel, but rather to a big box next to the main panel into a 200 amp disconnect switch. I can turn the entire stable off from my basement in this manner. From the disconnect switch, the 200 amp wires go underground, to the underground box I have talking about in my lawn, about 150 feet away. There, there is an existing splice (I will post a picture tomorrow). Then, they go back into a continuing conduit and run another 150 feet, under a driveway, and then up into a finished wall in the stable into a 200 amp panel which distributes the load throughout the stable.
Hope this additional description helps.

What you want to do is permissible if done properly. The entire underground installation has to be done using methods and materials suitable for a wet location. The wire has to have a "W" in the designation and your joints have to be water-tight. I would put drain holes I the bottom of the junction box also. I still think that the size of the junction box may be an issue since it was installed as a pull box and not a junction box.

Here are pictures of the box, inside and out, showing the connections. It is about 16" x 12".

I believe you box is too small to meet code. Here is the code section..


(2) Angle or U Pulls or Splices.

Where splices or where
angle or U pulls are made, the distance between each raceway entry inside the box and the opposite wall of the box shall not be less than six times the metric designator (trade size) of the largest raceway in a row. This distance shall be increased for additional entries by the amount of the sum of the diameters of all other raceway entries in the same row on the same wall of the box. Each row shall be calculated individually, and the single row that provides the maximum distance shall be used.

OK, that is good information for me. I don't understand the metric (trade size) terminology. These are 2 or 3 inch conduits. So how would that be calculated?

A larger box can certainly be installed when we make this change.

Just use six times the 2" or 3" trade size and you will be able to size your box.

Thank you all for your help. The electrician came out today and we are planning on proceeding in accordance with all of your comments.

I bet the electrician was just thrilled out of his mind when you started talking about what you were told on a HI forum!

I'll be a thorn in the thread by saying no one can really answer the posed question (does code allow it) since we don't know what code (or edition) applies to this particular structure/situation. I'm always amazed that people try to answer such questions without knowing such information. Now if the question was whether this was a safe and acceptable practice then I'd take a stab at answering it.

Then I guess you will continue to be amazed...give it a rest oh holy one!

No.

Neither the installation existing presently as you multiply describe and photographed nor what you further propose are compliant with Art. 547 (neither are the suggestions by others on this thread), and are further violative of applicable Articles in Chapters 1, 2, 3 & 4.

Edit: correction in blue (changed "is" to "are")

Since I am just a homewoner looking for more specific knowledge, can you give me a more full explanation of the reason why it is violative? The reason I even posted this question was to learn the details. Thanks.

See NFPA 70, The National Electrical Code, 2008 Edition (applicable in DE with minor amendments regarding 120V receptacles in homes and manufactured homes), Article 547 for starters, note the Article has its own set of definitions which superceed those in Chap.1. Chapter 1, 2, 3 & 4 apply to all installations. Chapter 547 has further requirements and restrictions.

You can view at your local library, New Castle County department (or if in the actual city limits at their permit office, or even on-line (in view only mode) for free at NFPA you'll have to register at the site to view (not join as a member of NFPA); the advantage being after doing so, you can also view all of the NFPA codes the First State has adopted (not reflecting of the specific ammendments) and following registration, and comfirmation (via email prompt) you'll be able to log in when prompted and view them at any time.

Originally Posted by James Duffin

Then I guess you will continue to be amazed...give it a rest oh holy one!

Yeah I know. It's a bone I always pick at and probably always will.

I am just looking for a summarized understanding of "why" it is violative. Thank you for pointing out where I can find the code.

This is to reply to Eric Barker's post a few back....so as the homeowner contemplating this arrangement, is it a safe and acceptable practice? (I understand you comment about the applicable code and the difiiculty of properly answering hat question)