subpanel 140ft from main panel

[curtis9]

I have built a small 14x20 pole barn to house a indoor wood boiler and a years worth of wood. I need to run power out to it and install a subpanel. The wood boiler manual states that it needs to have its own 30 amp circuit and then I want to have one or two wall plugs and lights inside the barn and one outside. The house has a older Zinsco 200 amp service panel 140 feet from the new barn, 40 feet inside and about 100 outside. What size wire would I need to run to the new subpanel? And would you use cu or al wire?

 

[pattenp]

I suggest doing at least a 50 amp feed. For the 140' distance you can get by with #4 aluminum for 50A. Are you looking to do direct bury or conduit? Mobile Home Feeder(MHF) is a good option and can be direct buried or run in conduit. The smallest MHF comes in is 2-2-2-4 and will give you plenty of amp capacity and cost around $1.50 a foot. One thing is the MHF needs to be in conduit where inside the structure.

 

[curtis9]

I suggest doing at least a 50 amp feed. For the 140' distance you can get by with #4 aluminum for 50A. Are you looking to do direct bury or conduit? Mobile Home Feeder(MHF) is a good option and can be direct buried or run in conduit. The smallest MHF comes in is 2-2-2-4 and will give you plenty of amp capacity and cost around $1.50 a foot. One thing is the MHF needs to be in conduit where inside the structure.

I think I would just perfer to do direct bury for the ease factor. So would you go with al instead of cu wire? And can you hook the #4 wire up to a regular 50 amp breaker in my house or does it need to be a special one due to the size of the wire? And since this is only for 120v how many wires do i need?

 

[pattenp]

Typically a 50A breaker will take up to a #2, so #4 will fit. The thing is I don't know of any direct bury other than UF-B in copper for smaller size wire to get 50A. #6 is the largest you can get in UF-B and will work for 50A. You can get UD cable in #4 aluminum, but UD has to be terminated on the outside of the structure, it's not to be run inside. The 6/3 UF-B appears to be your easiest solution. The UF-B can be run inside just like NM-B (Romex).

Edit: Direct bury is 24". And make sure the trench is clean, no stones in the backfill. And use marking tape 1ft above line.

 

[curtis9]

Ok so #6 uf copper wire and a single pole 50 amp breaker for the main panel is what i will need. Do i need a 6-2, 6-3 or 6-? wire?

 

[theoldwizard1]

I think I would just perfer to do direct bury for the ease factor. So would you go with al instead of cu wire? And can you hook the #4 wire up to a regular 50 amp breaker in my house or does it need to be a special one due to the size of the wire? And since this is only for 120v how many wires do i need?

Ok so #6 uf copper wire and a single pole 50 amp breaker for the main panel is what i will need. Do i need a 6-2, 6-3 or 6-? wire?

I think pattenp missed those 2 statement,

In the title you stated "subpanel" which implies 240V. That means a 2 pole breaker at the main panel. That also means 4 conductors, although code allows you to a small conductor for ground. If you are buying UF-B, it would be labeled 6-3. You will also need 2 - 8' ground rods.

MHF is a good choice because of cost, even though you need to run it in conduit inside the building. Check the price per foot on both. Measure twice before you have them cut and add an extra 10' or so.

Also, if you are using PVC conduit (recommended), make sure you buy Schedule 80 (extra HD) "sweeps" to transition from the bottom of the trench to the elbow going into the building. Standard, Schedule 40, conduit will not hold up to most string line trimmers.

 

[curtis9]

Ok, so a subpanel is 240v? Is there a way to run power out there without it being 240v?

 

[pattenp]

You can run 6/2 off a single pole 50A breaker to get just 120V and jump the input terminals of the sub-panel to utilize all circuit spaces in the panel. But if you are going to all the trouble of running this feed and have a sub-panel I highly recommend running 6/3 off a 2 pole breaker back at the house. Even if you don't use any 240V devices in the pole barn you will be splitting your 120V loads between two legs. I think if you just run 6/2 you'll regret it later. With 6/3 you'll have the ability to get 240V but that doesn't mean you have to use it. Now I'm assuming you have space in your main panel to add a 2 pole breaker.

Ok, so a subpanel is 240v? Is there a way to run power out there without it being 240v?

 

[pattenp]

And yes I had tunnel vision to being a sub-panel, so 240V.

I think pattenp missed those 2 statement,

In the title you stated "subpanel" which implies 240V. That means a 2 pole breaker at the main panel. That also means 4 conductors, although code allows you to a small conductor for ground. If you are buying UF-B, it would be labeled 6-3. You will also need 2 - 8' ground rods.

MHF is a good choice because of cost, even though you need to run it in conduit inside the building. Check the price per foot on both. Measure twice before you have them cut and add an extra 10' or so.

Also, if you are using PVC conduit (recommended), make sure you buy Schedule 80 (extra HD) "sweeps" to transition from the bottom of the trench to the elbow going into the building. Standard, Schedule 40, conduit will not hold up to most string line trimmers.

 

[curtis9]

6-3 wire it is then. Just called a local electrical supply place and the 6-3 uf is $2.10 a foot. Ill get around 150ft of that and a double pole 50 amp breaker, 2 8' ground rods and a small subpanel.
Thanks for all the help guys!

Edit: Any recomendations on a panel for inside the barn?

 

[pattenp]

Just an FYI. If you plan to put more than 6 breakers in the sub-panel then you will need to also have a main disconnect or a main breaker panel. If 6 or less breakers you can use a main lug panel. NEC requires a main disconnect at the building if it takes more than 6 flips of switches to disconnect all the circuits in the building.

 

[pattenp]

If no more than 6 breakers use something like this...
http://www.homedepot.com/p/Square-D...-No-Door-HOM612L100FCP/100149777#.UlRl1NJONY4

If more than 6 breakers then use something like this...
http://www.homedepot.com/p/Square-D...with-Cover-HOM816M100C/100161591#.UlRmNtJONY4

 

[curtis9]

I'm pretty sure I will have less than 6 breakers in the barn. Probably only 3 or 4.

I really appreciate your time and knowledge in helping me with my project.

 

[wyliesdiesels]

The following is often forgotten and overlooked: dont forget to isolate the neutral bar in the subpanel from the enclosure and ground bar. You will likely need to buy a separate ground bar that is U/L listed for the brand of panel u buy!

The ground rods need to be connected together by one continuous wire from the last rod all the way to the panel. Use #6 solid bare CU. You can use a smaller GEC wire but it will need to be run in conduit for protection because #6 is the smallest size that doesnt need protection!!

 

[curtis9]

Thanks for the info. I will be sure to do all that when i am ready to hook it all up.

 

[curtis9]

Ok it turns out the boiler only needs a 15 amp circuit and not a 30. So for a 15 amp circuit for that and then a wall plug and a few lights what size wire would you recommend?

 

[pattenp]

For that, I'd do 30 amps using either #8 copper or #6 aluminum for that distance.

Ok it turns out the boiler only needs a 15 amp circuit and not a 30. So for a 15 amp circuit for that and then a wall plug and a few lights what size wire would you recommend?

 

[p_mori7]

150' of wire is cutting it close in my opinion. You need to factor in all vertical travel distance (downwards along house foundation for example, + 24" each end for burial, upward along pole barn side, etc...)

 

[Sureshot]

Do you need 240V?

Also sleeve the conduit where it comes out of the ground on both ends from below frost to a foot above ground. Cheap and easy protection from "pullout" and damage.