100 amp service for detached pole barn

[craig1701]

Hello everyone,
This is my first post
I am going to install a 100 amp service in a new 30x40 pole barn workshop
this fall hopefully and need some electrical advice
I have a 200 amp service in the house right now and will be putting in an underground service to the pole barn, It is 115' from the service panel in the house to where I am going to put the new service panel. Do I just get a 100 amp double pole breaker and put that in my 200 amp service panel and run the lines off of that? If so what would be the correct wire type and size to do this? Thanks Craig

 

[pattenp]

Knowing where you are located will help. But I suggest using 2-2-2-4 Al Mobile Home Feeder with a 90A breaker in the 200A panel and use a 100A Main Breaker Panel in the pole barn. I believe this is the most cost effective way to go.

Edit: The MHF is direct bury and will need to be in conduit where exposed above ground and inside the structure unless you transition to SER in a Jbox just inside or outside of the structure.

 

[NHBandit]

Knowing where you are located will help. But I suggest using 2-2-2-4 Al Mobile Home Feeder with a 90A breaker in the 200A panel and use a 100A Main Breaker Panel in the pole barn. I believe this is the most cost effective way to go.

Edit: The MHF is direct bury and will need to be in conduit where exposed above ground and inside the structure unless you transition to SER in a Jbox just inside or outside of the structure.

This ^^^^^ is exactly what I did with my 30x40 pole barn here in Tennessee. Lowes has a 100A sub panel "kit" made by Square D that comes with the breakers for around 80 bucks that works well for the garage. They do not stock most 90A breakers for the main panel in the house since it's not all that common but a trip to an actual electrical supply place got me fixed up on that. The wire was cheaper at the electrical supply place as well. It pays to shop around.

 

[raceman17]

This ^^^^^ is exactly what I did with my 30x40 pole barn here in Tennessee. Lowes has a 100A sub panel "kit" made by Square D that comes with the breakers for around 80 bucks that works well for the garage. They do not stock most 90A breakers for the main panel in the house since it's not all that common but a trip to an actual electrical supply place got me fixed up on that. The wire was cheaper at the electrical supply place as well. It pays to shop around.

I did the same thing in my 40x80 building. The kit from Lowes is the way to go.

If i remeber correctly you will have to remove the "metal strap" piece that connects the ground bar and common bar together. You will have to intall a grounding rod outside the new building.

 

[pattenp]

I believe you meant to say "will have". Ground rod(s) are required at the structure.

I did the same thing in my 40x80 building. The kit from Lowes is the way to go.

If i remeber correctly you will have to remove the "metal strap" piece that connects the ground bar and common bar together. You will not have to intall a grounding rod outside the new building.

 

[theoldwizard1]

Knowing where you are located will help. But I suggest using 2-2-2-4 Al Mobile Home Feeder with a 90A breaker in the 200A panel and use a 100A Main Breaker Panel in the pole barn. I believe this is the most cost effective way to go.

Edit: The MHF is direct bury and will need to be in conduit where exposed above ground and inside the structure unless you transition to SER in a Jbox just inside or outside of the structure.

One more What He Said ^^^^^^ !!

Don't be confused by the size of the "main" breaker in the panel in the barn or even the sum total current of each of the individual circuit breakers versus the breaker feeding the wire from your house panel.

The 90A breaker is sized to protect the 2-2-2-4 MHF cable and will likely be the overall limiting factor. Even if the individual breaker in the barn panel add up to 150A, it is highly unlikely that you will exceed the 90A breaker in the house (based on "average" loads, but only you know your actual loads).

Breakers are sized to protects the wire from the breaker to the load or the next breaker which ever comes first.

 

[Modifieddriver]

Good information. I'm getting ready to do the same. Just had the power company hook up to my meter base on shop #1. Now have to run underground 100+ feet to shop #2.

Picked up the trenching machine yesterday. I'll do that, the electrician will hook up the wire.

Let the fun begin!!!!!!!!!

 

[VRR]

You need an outside disconnect and ground rods at the barn. Segment ground and neutral buses in the barn box.

 

[pattenp]

Depending on local requirements he may or may not need an outside disconnect. NEC does not require the disconnect to be outside.

You need an outside disconnect and ground rods at the barn. Segment ground and neutral buses in the barn box.

 

[sands35]

Trenchers are fun! Just make sure you call your local "call before you dig" number.

 

[craig1701]

I have some changes to the distance of the run. I need to move the pole barn further away from the main box to meet the city codes for setbacks and now the run will be 250 ft
Can I still get by with the 2-2-2-4 at that length? I will be using a 240v air compressor that requires 22 amps and a Miller welder 251 that I would use once and awhile that needs 42 amps at 60% duty cycle along with the typical lights and 120v receptacles
and no air conditioning. Thanks for your help

 

[pattenp]

Sorry to say this but 250' is a deal killer for #2 MHF. The best it will give you is about 50A with not having too bad of voltage drop. You need to jump up to #2/0 MHF to have closer to 80A-90A of power with 3% or less voltage drop. These are just ball park figures. The 2/0 should fit a 100A breaker.



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[craig1701]

Thanks
Menards has 4/0-4/0-4/0-2/0 mhf for $3.19 a ft which I can afford
What would I use for the correct breaker in the 200 amp panel in the house and what would I use to connect that size of wire to the breaker?

 

[pattenp]

You need to read the specs in your panel to see what the largest breaker that can be used. You may find that the largest is 125A. You will need reducer pins or reducer/splicer to add a short 2/0 tap to fit the breaker. 4/0 is going to be a bear to work with.


Edit: Depending how you can run your feeder you may be able to run a short section of 2/0 Al SER out of the panel to a big junction box and splice to the 4/0 for the long haul to the shop. The max amp because of the section of aluminum 2/0 will be 135A.

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[Aceman]

Have you contacted the power company yet and asked how much a second service would cost?

 

[justin1795]

I also was pricing menards wire for something similar. I found that menards only has 4/0 in 3 wire plus ground all there other wire smaller are 2 wire plus ground. depending on how you end up home depot has 1/0-1/0-1/0-2for 2.74 per foot.

 

[zmaxmotorsports]

I did the same thing in my 40x80 building. The kit from Lowes is the way to go.

If i remeber correctly you will have to remove the "metal strap" piece that connects the ground bar and common bar together. You will have to intall a grounding rod outside the new building.

Depending on brand of panel youre using in the pole barn you can just leave the green bonding screw out and add a separate buss for the ground wires to keep the neutrals and grounds separated in the sub panel.

 

[sberry]

It not a sub, its a new service to a detached structure from an existing service.

 

[zmaxmotorsports]

It not a sub, its a new service to a detached structure from an existing service.

Its being fed from an existing panel in his house,that makes it a sub panel.

 

[sberry]

I would like to see 1 place in the book its called that?

 

[dledinger]

Not a service per article 100.