Power to barn and a generator from house

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  #1  
Old 11-24-18, 09:17 AM
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Question Power to barn and a generator from house

Sorry, this may be a long post but trying to figure out best plan of action:

Bought a house that was wired for 200A service but has a 150A panel with 5 open spots.

Want to build a pole barn (30x40 and 120ft from house) and have power fed to it from main panel with 100A service)

Also would like to have generator by pole barn to feed house in case of outage due to living out in the country.

Would my best course of action be:

1. Install 200A panel in house
100A breaker on panel in house to 100A panel in pole barn
Transfer switch in house running from generator by pole barn

2. Install 100A breaker in house
Run wiring from 100A in house to 100A panel in pole barn
Double pole 30A breaker with interlock that will feed house from pole barn

3. Install 50A breaker in house
Run wiring from 50A in house to 50A panel in pole barn
Double pole 30A breaker with interlock that will feed house from pole barn

4. PUNT!!!!

Thanks for all of your inputs on what is the best and the safest.
 
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  #2  
Old 11-24-18, 09:57 AM
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From just your post, I'd go with option 3. Running wire 120' to service more than 50A will get expensive quick.

However there are a few questions that should be answered before a definite answer is given.

What size is your generator?
What are you wanting to run off your generator?
What are the power requirements/needs for your pole barn? Lights only? Welder? 220v saws?
Will the equipment in the barn be used occasionally or regularly?
Are you burying the wire or running it overhead?
 
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Old 11-24-18, 10:01 AM
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All are the valid option, except you have to run separate line for generator feed from pole barn to your main panel in all cases. You cannot use same line because there is no way to interlock your main breaker.

You will also have to install grounding rods if your barn is detached from the house.
 
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Old 11-24-18, 10:24 AM
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8750 running power

Would like the ability to be able to control the panel in the house if there is a need but would settle for well, crock, corn stove, living room, 2 bedrooms and 1 bathroom

Pole barn will have 8 led shop lights inside, 4 exterior led day/night lights, 8-10 outlets. No welder but will have an air compressor

Pole barn equipment used occasionally, except for the exterior lighting

Wire is being buried.

What wire would you recommend for the run underground for the 50A?
Should the double pole 30A be on the house or the pole barn so I do not backfeed the line?
 
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Old 11-24-18, 10:27 AM
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OK. So a 50A from house to pole barn to feed the pole barn.

A double pole 30A at the house, with interlock, that runs from the power inlet box at the pole barn to the house.

What size wire for the 50A?

What size wire for the wire from the power inlet box for the generator to the double pole 30A at the house?

All be underground. Can i run them in the same trench or different?
 
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Old 11-24-18, 01:31 PM
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Are you planning to run conduit between buildings or do you plan to do direct bury? I suggest PVC conduit, it's cheap protection.

If doing conduit my choice of wire would be #4 Al XHHW-2 for the 50A-60A feed and #8 Al XHHW-2 for the 30A-40A generator inlet power back to house. If direct bury same sizes in RHH/RHW-2/USE-2.
 
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Old 11-24-18, 01:45 PM
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I plan on running the wire in conduit.

The #4 aluminum will not have a problem will not have a problem going into the double pole 50A breaker?
 
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Old 11-24-18, 01:52 PM
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I would recommend a 60 amp breaker in the main panel with the #4 aluminum wire (XHHW) which is allowed per NEC 310.15(b)(16). Also 60 amp breakers are widely available.

The panel in the house should able to be left as is.

Use a 100 amp panel in the pole barn with a main breaker as they are very reasonable in price.
 
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Old 11-24-18, 02:00 PM
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I verified the max wire size for 50A and 60A looking at Square-D breakers as an example and it is #2 max. If using individual wires such as the XHHW for the entire run it needs to be in conduit from panel to panel. All conductors can run in same conduit, make sure conduit is sized properly.
 
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Old 11-25-18, 08:02 AM
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... except you have to run separate line for generator feed ...
Your situation is an exception to a rule that only one feed may run between the main building and an outbuilding.

Or you can use the semantic difference that you have one feed (as a branch circuit) from the main house to the barn (subpanel) and you have one feed from the barn (generator pad) to the main house (panel interlock or transfer switch).
 
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Old 11-25-18, 08:36 AM
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Your situation is an exception to a rule that only one feed may run between the main building and an outbuilding
That is a good point, but I wonder if it would be allowed as only one feed would be active at any given time. I do like the idea of having the feed from the generator entirely separate from the feeder from the house to the pole barn which would solve any issue. The pipes could be still run in the same trench.
 
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Old 11-25-18, 06:53 PM
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When the generator is running (because utility power has failed) and something in the barn is in use then both feeds will be active.
 
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Old 11-26-18, 08:08 AM
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Originally Posted by AllanJ View Post
When the generator is running (because utility power has failed) and something in the barn is in use then both feeds will be active.
Regardless if something in the barn is being used or not the branch feeder to the barn is live via the generator powering the main panel in the house. The power inlet for the gen is not considered a supply feeder to the barn, it's a supply feeder to the house. There is only one supply feeder to the barn. The NEC says there is only to be one feeder that provides power to a structure.
 
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Old 11-26-18, 08:52 AM
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I agree the separate set of feeders for the generator is the correct way to install this to ensure the main can be fully interlocked.
 
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