Replacing wiring nightmare!

[Ihateclevernames]

Gents, I am helping my neighbor sort through a wiring mess that was left by the previous homeowner.

He has several outbuildings that are powered by a single home made extension cord that was created from 10/2. The distance of the buildings is about 250' and he plugged it into the in law suite which has a 100A subpanel inside it. In total, this cord powered approximately 16 outlets and 4 lights between 2 buildings. He has all of the outlets recessed inside of the walls in both buildings and a strand of 12/2 romex running between the 2 buildings strung up between trees.

Needless to say, it all needs to go.

So, here is what I am thinking.

Setting up a smaller 30A subpanel in one of the outbuildings and either running the appropriate underground cable to the building and then actually building circuits from the subpanel box for each building and desired output in specific locations.

Basically, all he wants is about 12 20 amp outlets, 4 lights and potentially a welder in the future. He may be able to sacrifice the welder if the cost seems to be too high for the appropriate cable. I realize that we could cut down on the cost and ditch some outlets and just run 10/2 underground in order to account for the voltage drop and then have a single dedicated circuit on both buildings.

Thoughts?

 

[wyliesdiesels]

Wow what a mess.

Youre gonna need some large sized wire due to the distance.

What is the distance between the outbuildings?

If theyre closer to each other than the house, i would:

Run a 2/0 MHF feeder out to one of the buildings, put in a 100a subpanel along with 2 ground rods. Then run a smaller feeder from this subpanel to another into the second outbuilding.

This will give ample capacity for both buildings including 240v to run a welder or compressor.

U will only be able to run one circuit to each building meaning u cant have all the branch circuits originate in one building and feed them to the other.

If thats too expensive, then u could aize it down. But if u get a larger welder, 30a wont cut it.

 

[Ihateclevernames]

Wow what a mess.

Youre gonna need some large sized wire due to the distance.

What is the distance between the outbuildings?

If theyre closer to each other than the house, i would:

Run a 2/0 MHF feeder out to one of the buildings, put in a 100a subpanel along with 2 ground rods. Then run a smaller feeder from this subpanel to another into the second outbuilding.

This will give ample capacity for both buildings including 240v to run a welder or compressor.

U will only be able to run one circuit to each building meaning u cant have all the branch circuits originate in one building and feed them to the other.

If thats too expensive, then u could aize it down. But if u get a larger welder, 30a wont cut it.

He may have to skip the welder and just worry about lights and tools.

I should have stated that these are more of sheds than they are buildings. Each one is less than 200 Square feet.

Any idea on how we can do this without having to put in such a large subpanel?

 

[wyliesdiesels]

U can use a smaller subpanel if u want.

My comment was only a suggestion.

If youre gonna feed one building from the other i would suggest a minimum of 50-60a. With that u could run a small compressor and some lights and tools or a smaller welder.

 

[pattenp]

For the distance the smallest I suggest is #4 aluminum on a 30A feeding breaker to a small 100A main breaker panel in the first primary outbuilding and feed other building from there. Using a 30A or less welder should be fine from the first sub-panel. You'll find that a 100A panel is the smallest you'll get with a main breaker with at least 10 spaces. They can be purchased for under $30. Here's an example... http://www.lowes.com/pd_89671-82364-BR1020B100F11RN_1z0uy04Z1z10wgmZ2z8vn__?productId=3129821&pl=1 This is all off the cuff without good detail of what power usage is going to be in each building. If doing direct bury use type (RHH / RHW-2 / USE-2) aluminum wire.


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[Ihateclevernames]

So could he use a mobile home feeder cable out there that has all of the wires sheathed?

I am assuming that if he adds a subpanel out there, he will need to add grounding rods as well?

 

[pattenp]

So could he use a mobile home feeder cable out there that has all of the wires sheathed?

I am assuming that if he adds a subpanel out there, he will need to add grounding rods as well?

Mobile Home Feeder (MHF) is not sheathed. It needs to be in conduit where exposed above ground and where installed inside the structure. SER cable is sheathed but is not allowed below ground. But, yes he can use MHF. With sub-panels in the outbuildings the outbuildings will need ground rods.

 

[Ihateclevernames]

Mobile Home Feeder (MHF) is not sheathed. It needs to be in conduit where exposed above ground and where installed inside the structure. SER cable is sheathed but is not allowed below ground. But, yes he can use MHF. With sub-panels in the outbuildings the outbuildings will need ground rods.

Gotcha, so he can run MHF inside conduit to the buildings and go from there. I think the cost on the MHF is a little bit less than other options.

I think overall, we are going to look at a 30A feeder breaker as previously mentioned. Which will allow him to to run a few 15A breakers in the building that will power his lights and outlets.

 

[wyliesdiesels]

Gotcha, so he can run MHF inside conduit to the buildings and go from there. I think the cost on the MHF is a little bit less than other options.

I think overall, we are going to look at a 30A feeder breaker as previously mentioned. Which will allow him to to run a few 15A breakers in the building that will power his lights and outlets.

U can have branch breakers that add up to more than the main breaker rating.

 

[Ihateclevernames]

U can have branch breakers that add up to more than the main breaker rating.

So the school of thought on that is that we could have several circuits running off of the 30A main breaker, as long as the total amount of usage does not max out the 30A main, I.E. if 3 branch breakers are running 12A each at the same time, we are good.

Am I in the ball park?

 

[wyliesdiesels]

3x12a = 36a so not exactly if all the breakers are on the same leg.

But it depends on the voltage.

If everything is 120v u could have 60a of capacity for 120v.

But thats not what i was getting at.

U could have for example 100a worth of breakers adding them all up and as long as the load is less than 30a combined you will be fine.

 

[pattenp]

One issue you will have using MHF with a 30A feeding breaker is that #2 is the smallest MHF and that is too large to fit in a 30A breaker. A 50A breaker may be as small as you can go with #2. Wire size to breaker size is different from brand to brand.