Hi,
I have a 400A 230V service that runs from a transformer on a pole to a meter box located on the side of the house. Out of the meter enclosure are two 2/0 cu cables that run to two separate 200A service panels in the basement. One panel contains all the breakers for the house. The other panel is empty. The empty panel was originally intended for the garage and barn but seems like it is not the correct approach since the power to the other outbuildings would be limited by the breaker in the panel. My idea is to disconnect the feed to the unused panel and instead run a 4/0 four wire aluminum URD direct bury cable to the first outbuilding, the shop. I would like to mount a nema 3R enclosure on the outside wall of the shop and run a 2/0 feeder into the shop 200A panel. Then continue the 4/0 URD to the barn and terminate it at the service panel. Does this approach make sense? If so how do I splice into the 4/0 in the 3R enclosure? The distance from the house to the shop is 80 feet. The distance from the shop to the barn is 160 ft. The shop will have a air compressor, welder, lights and frig. The barn will have a water heater, fans, frig and high bay lights. I'm guessing at about 100A per outbuilding. Any insight would be appreciated.

Devils advocate:

What's the distance from the house to the barn?

What about two 100 A breakers in the unused panel?

Before we get into voltage drop calculations.

Reminder that the total amps of all the breakers don't have to equal the main breaker.

You'll need 4 wire feeds and disconnects and ground rods at each detached structure. 100 A is probably the max breaker that can be fitted in the panels.

In your scenereo, you could place a 100 A breaker in the shop for the barn, but I'm still worried about voltage drops. You might have to step up the voltage for transmission.

Aluminum or copper?
Distribution of 240/120 loads in proposed panels.

The distance from the house to the shop is 80 ft. The barn is beyond the shop and the distance from shop to barn is 160 feet. Can I run the 4/0 four wire aluminum URD from the house at the meter all the way to the barn (240 ft) by way of a disconnect at the shop? I know the 4/0 is a little heavy, but I can get it for about $2/ft in aluminum, that should help with the voltage drop over that distance.

Aluminum has higher resistivity than copper, so copper gives the lowest voltage drop.

There are a number of calculators here: www.electrician2.com.

What your looking at is a 3% drop at 240 V and you should aim for balanced 120V loads, if possible.

Using this http://www.electrician2.com/calculat..._distance.html calculator, I got maximum distances of:

~180 feet at 200 A and ~360' at 100 Amps

You can have a disconnect for the barn at the shop, but you also need one at the barn, since this is a detached structure. Also, since detached, it requires a ground rod at each structure.

You will have issues matching the wire to the breaker lugs, so you may need to splice to a short length of a lighter gauge wire.

A reminder, is that you can use, say a 200 A panel at each location with the main breaker rated at 200 A and fed by a 100 A source. That breaker becomes the disconnect.

So, two 100 A services seem OK and so does one 100 and one 200 amp service, but you can't get 200 A breakers for the 200 Amp panel.

Tough call. Entertain high voltage transmission too. This may be better overall since the neutral and ground bond will be made at each building.

Talk the ideas over with an electrician in your area and see if you can do most of the work. Dig, pull wires, etc. Let him pull the permits, do the design and make the final connections.

So if I understand you correctly,
1) I could run out of the meter box at the house with the 4/0 aluminum URD in conduit until I get down into the trench.

2) Run the 80' to the shop, use a 90 deg elbow and conduit up to a nema 3R enclosure mounted to the outside of the shop.

3) Mount a 200A service panel on the inside wall of the shop. This will serve as the disconnect at the shop.

4) From the nema enclosure at the shop, splice a 2/0 service entrance cable from the 4/0 to the service panel in the shop.

5) Additionally, splice the 4/0 cable to the barn at the same splice. This is a three-way 4/0, 4/0, 2/0 splice.

6) Run the 4/0 out of the nema enclosure at the shop to the barn(160').

7)Mount a 200A service entrance panel with disconnect in the barn, and connect the 4/0 feeder to it. This may require a splice down to 2/0 to fit the lugs in the service panel.

Question
Does the 4/0 URD need to be four wire? The power all the way to the barn is tied to the meter distribution box at the house. I have another farm that has a center pole wiring arrangement. From the transformer, a 400A cable runs to a pole and through a CT with a meter at the bottom. At the pole there is a 4-way junction or splice. The house, barn, and shop are all fed off the 400A feeder. The house, barn and shop each have their own service panel with disconnect. Each of the three loads are two conductors and a neutral with ground rods at each panel. This wiring was done many years ago so I'm not sure if it is up to current code. What I am trying t do is a buried version of this.
Again, thank you for thoughts on this.

Part 1.

Quote:

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Originally Posted by worktofarm

So if I understand you correctly,
1) I could run out of the meter box (The 200 A breaker) at the house with the 4/0 aluminum URD in conduit until I get down into the trench 18" deep min.

2) Run the 80' to the shop, use a 90 deg elbow and conduit up to a nema 3R enclosure mounted to the outside of the shop. Run direct to the shop, 200 A main breaker and will serve as disconnect.

3) Mount a 200A service panel on the inside wall of the shop. This will serve as the disconnect at the shop.

4) From the nema enclosure at the shop, splice a 2/0 service entrance cable from the 4/0 to the service panel in the shop. Probably best to put a 100 A breaker in the shop panel to feed the barn. You can splice in the panel.

5) Additionally, splice the 4/0 cable to the barn at the same splice. This is a three-way 4/0, 4/0, 2/0 splice. Nix

6) Run the 4/0 out of the nema enclosure at the shop to the barn(160'). Nix

7)Mount a 200A service entrance panel with disconnect in the barn, and connect the 4/0 feeder to it. This may require a splice down to 2/0 to fit the lugs in the service panel. The 200 A breaker will serve as the disconnect. It's fused upstream at 100 A.

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There are fewer splices. Drawback. Disconnect at shop disconnects the barn.

You could consider a meter box with a cover plate which has two 100 A breakers in it. See Midwest Electric Products, Inc. which could make things a bit cleaner with separate disconnects. That could be mounted outside or inside the shop.

Part 2: Thinking

Sorry, I'm still confused. Let me restate what the situation is at the house. From the transformer, there is a 400A overhead cable that runs to a entrance service box with meter mounted to the outside of the house that looks very much like this:

Midwest Electric Products, Inc.

There power is disconnected from the main by pulling the meter. There are no breakers in the SE.

Out of the bottom of the SE are (2) 2/0 service entrance cables that run to (2) separate 200A service panels with main breakers in the basement. One is used for the house, the other is unused. My plan was to completely remove the unused panel and instead run the new 4/0 URD cable from the bottom of the SE at the house to the Nema 3R enclosure at the shop. Power to the shop would be disconnected by pulling the meter(same as power to the house). Power in the shop would be disconnected by the 200A service panel main breaker mounted on the interior wall. Would this fly?

Thanks again

Given what you said above, then the Utility makes the rules. I believe burial depth will increase to 36" and a disconnect will be required within 10' of the house. SE rated wire will have to be used and your at their mercy. They can require larger wire guages than the NEC. They may require a specific brand of disconnect. They will almost guaranteed to do the termination.

They usually require a specific meter socket with a particular sticker, for instance. Local suppliers typically stock what the utility requires.

They may not even allow you to trench or lay the cable. They could require a specific brand cable that they supply. They determine the distance the ground rod has to be and the dept of the risers and the tpe of pipe used.

Your, in esscence, adding underground service from a pole supplied service to two other locations.

They may find it easier to tap into the pole with pole mounted disconnects.

In any event, when the SE panel is located more than 10' from the panel a disconnect is required. Pulling meters is reserved for the utility company only. Some localities are requiring disconnects anyway becaue it's easy then to turn off the power to the house/building in the event of a fire.

Two separate underground feeders from the pole may not be a bad idea either. They may put CT's at the pole to meter everything.

They could decide, to run a high voltage line underground to the midpoint between the garage and the barn, mount a pad transformer, and then feed from there. That makes the service 80' and 80' + a high voltage underground feed. That's probably the best and most expensive option.

There are options.

Contact the utility. Have them come out and decide on what they will approve and what you can do. Report back your findings. Everything will have to service entrance rated to the panels and approved by them.

Report back.