Want to add 230V outlets to my barn

[mwood]

I've got a question for all those who are smarter with home wiring tham me. I'm looking at a welder (Christmas is coming up /forums/images/graemlins/wink.gif). I was thinking of getting a simple stick welder to learn with. All the ones I've looked at need 230V outlets. I would be using this welder in my barn.

Okay. So I need a 50A 230V line in my barn.

My barn is wired as a sub to my main panel in the basement. I have 100A service coming in the house. There are 2 50A breakers tied together for the main cutoff. The breaker for the subpanel in the barn is tied into the main with the same (2 50A breakers).

All the wiring is in 1.5 - 2 inch conduit through my basement and out the side of the foundation. In the barn, there is conduit coming up the wall from the ground and into the subpanel. The only place I can see what's in the conduit is a small access panel about 2 inches by 6 inches right where the conduit exits the house. Inside, there are three thick wires but I see no markings on them.

For some reason, the subpanel in the barn has a single 40A breaker as its main.

(Sorry this is long, but I'm trying to give an accurate picture).

Questions:

1. Is it safe to assume that the wires to the subpanel (in the conduit) are rated to carry the full 100A (since they are on a 100A breaker in the main panel)?

2. Is it safe to assume that I have 230V in the barn?

3. Can I just change out the main in the barn to something like 80A and add a 50A 230V breaker to the panel to run the welder?

I do have a voltmeter and work at my day job as a computer engineer doing lots of work on embedded circuits. We just never have this much current and i'm really unfamiliar with how a home is wired (but can debug a motherboard... go figure).

Thanks for the help,

Mark

 

[EddieWalker]

Adding a breaker and outlet is a pretty straightforward job, but from reading your questions, I'd highly recomend you DON'T attempt it yourself.

It's real easy to make a mistake or even worse, get hurt. What's a trip to the hospital or a fire gonna cost compared to a few hundred dollars to have it done right?

An electrician, or even a handymand can do this for you fairly cheaply and you wont' have to worry about it.

Why 50 amps? Mine outlet for my AC/DC arc welder is 30 amps.

Eddie

 

[BB_TX]

Rule #1 - Never assume anything.
The 40 amp breaker is probably sized to limit how much the barn can pull from the main panel since the main is only sized for 100 amp.
Wiring on the load side of a breaker should be at least large enough to carry the rated load of that breaker. You can't down size the wire until you go thru another circuit protector (breaker or fuse). Let me rephrase that. You are not supposed to down size the wire until ...........
My welder also specifies a 50 amp breaker and that is what I have. But I never run it anywhere near the highest current rating so I am sure I never pull any where near the 50 amps.

 

[mwood]

Eddie:

Thanks for your concern! I've replaced breakers before -- just never 220V. I've also wired a garage before. Just never 220V and since it was an attached garage, I didn't have to worry about what was run under the ground.

I guess my main question is how do I make sure of what is buried? Re-reading my initial post, I do come off as somewhat of a newbie regarding electrical work. I also realized that since there were three wires run to the barn, that means that I do have 220V if I get the right breaker.

Anyway, I'll stay tuned if anyone else has any idea of how to check what's buried (other than digging it up /forums/images/graemlins/tongue.gif)

Thanks for the help so far!

Mark

ps. I was looking at a 50A breaker since that's what every welder I've looked at specifies. Chances are, I'll never need that much since I won't be turning it up all the way, but I would like to know that I could.

 

[LarryD]

<font color="blue"> I guess my main question is how do I make sure of what is buried? </font>

You could verify wire size at either end (assumes the wire is continous from main to sub, no hidden changes /forums/images/graemlins/mad.gif) with this wire gauge. Being an EE you'll be able to evaluate available amperage.

 

[HomeBrew2]

The more I read, the more confused I get /forums/images/graemlins/wink.gif
Let's take the barn wire capacity question:
I'm assuming that your breaker boxes have an outside hinged cover and an inside screwed on cover. When you remove the inside cover (careful, it's kinda juicy in there~main breaker off) you should have full access to all the wires ... you need that access to add a breaker of change a bad one. If you disconnect the wires from the barn feed, you can use a wire gauge template, or mic or calipers to find the size (you may need a decimal to wire gauge chart). Then you need to consult a wire table to determine the correct wire size for the number of amps and distance of the run. Then you need to consult an "ampacity of copper wire" table to verify that the wire size from the first table is actually able to carry that current ... if not, a larger size should have been used. In the end, the breaker needs to be sized based on the wire capacity that you have.
Clear as mud?

 

[BobReeves]

If you can carefully remove the front panels from the breaker boxes in the house and in the barn you should be able to see the wire and be able to tell us what you see or better yet post pictures.

What makes me think you may have a larger project than you think is the single large breaker in the barn. Is it really a single breaker or a dual with one handle.

If it is trully is a single you might need to replace the whole box in the barn.

 

[JustGary]

If I remember right, I used #6 Aluminum for the ~50 foot run from my house to my shop for 100 Amp service. It's been a long time, but I must have gotten that wire size from a book somewhere. It helped that that's the size wire I had hanging on the wall of my shed....

If you pull the panel cover and take a picture of what you have in the barn, we can probably talk you through it some more. Please be really careful pulling the cover!

If you indeed have 40 Amp 220 service, you may want to just do as a previous poster said and install an outlet and start welding. You'll know when you get to 40 amps! I'm willing to bet you won't ever get near it.

- Just Gary

 

[mudcat]

</font><font color="blue" class="small">( If I remember right, I used #6 Aluminum for the ~50 foot run from my house to my shop for 100 Amp service. - )</font> I hope not.

 

[ericbx1500]

When I wired mine I used #8 thhn which will handle 55amps but since I have a 130' run I only used a 30amp breaker at my main panel with a sub panel in the pole barn. I ran two hot's and a neutrel from the main panel and installed two grounding rods at the barn.