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Old 03-02-2010, 09:44 AM   #1
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How can I evaluate my 120/240 panel?


Hi everyone,

I'm considering picking up a used table saw that requires 240.

In my barn I have a 124/240 box. Actually, there's another box above it, that I believe is a master cutoff. I'd like to snoop around and identify exactly what I have. Only been in the home for a year.

Wondering if anyone has any tips.

The box is small. It has two large square receptacles towards the top of the panel. One is occupied, the other empty. I assume it's a pull-out that will contain a fuse inside.

Below these two receptacles are four inline thread in fuses. I believe they're all 15 amp circuits.

1. What can I do to verify that I have 240?
2. What's the deal with the two receptacles, and why is only one in use?
3. Is it "ok" to use this existing box? I'd hate to have to spend the money to modernize it before I have a good grasp on my future power needs.
4. I bought a screw in circuit breaker. Is this a joke, or will it work just as well as the old school fuse?
5. Do such saws typically have a special plug, or require hardwiring somehow?

I do have a multimeter. I will try to follow all the lines out of the box to take inventory of the receptacles.

I know, half of you are probably cringing, thinking "get an electrician", but I'm sure I can at least survey the installation w/o frying myself.

Thanks for any tips!

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Old 03-02-2010, 10:08 AM   #2
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How can I evaluate my 120/240 panel?


Take some pictures and post them.

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Old 03-02-2010, 11:41 AM   #3
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How can I evaluate my 120/240 panel?


Luckily, my Wife happened to be home.

Is this enough?

I'm guessing this means that I have one 240 line. I don't know where it goes to ... must be an outlet somewhere.
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Old 03-02-2010, 12:11 PM   #4
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How can I evaluate my 120/240 panel?


So the bus fuses feed the screw in fuses ?
What size are the bus fuses ?
Where is this fed from ? Main house ? Pole/outside panel ?

Myself I'd put a small breaker panel in & get rid of the screw in fuses
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Old 03-02-2010, 01:04 PM   #5
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How can I evaluate my 120/240 panel?


where went the red?
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Old 03-02-2010, 01:43 PM   #6
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How can I evaluate my 120/240 panel?


Yes, the bus fuse box, with 60 AMP fuses is ABOVE the panel and feeds it. The barn is fed from the house.

I have no problem upgrading this panel. I just have SO MANY projects going on at the moment, I'd love to be able to just plug a saw in and go with it for a bit.

I will have to root around the barn tonight to try to find where that 240 line goes. There's got to be an outlet on the other end.

I'm still in an exploratory mode with the house. Lots to discover...
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Old 03-03-2010, 09:34 AM   #7
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How can I evaluate my 120/240 panel?


After digging around in the barn last night, I believe I was mistaken in the assumption that I "have 240" in the barn.

I'm interpretting what I see as:

240 comes in from the house.

These two hot lines are used to supply four 14 AMP circuits.

Does this sound right, given the photos?

If so, does this mean I'm stuck? I assume I'd need to run additional lines in from the main box if I wanted 240 in the barn.

Thanks for the help, guys! Sorry if I'm misusing terms here. Not an electrician.
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Old 03-03-2010, 09:54 AM   #8
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How can I evaluate my 120/240 panel?


If the 240v coming in from the house is fed with 60a then you have enough power for a sub

I'd use a 100a min breaker panel & just feed it with the 60a

Now the issue is existing wires
If its #6 then you are OK with the 60a
With a new installation you are usually required to meet new codes
That means a 4 wire feed & 2 ground rods

Looking at the existing wire coming to the bus fuses it does not look like #6 wire
It looks like #10...which is only good for 30a
Someone may have upgraded the fuses to 60a
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Old 03-03-2010, 09:58 AM   #9
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How can I evaluate my 120/240 panel?


Thanks a lot for the help.

Even if it's not what I wanted to hear, at least now I know I should get an electrician if I want to be able to power a bigger saw out there.

I appreciate it.
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Old 03-03-2010, 10:17 AM   #10
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How can I evaluate my 120/240 panel?


Please note that if the feed wire is #10 then you could overheat the wire based on the 60a bus fuses

If it is #10 wire & you have a 30a breaker/fuse in the main panel feeding this then you are OK
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Old 03-03-2010, 07:08 PM   #11
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How can I evaluate my 120/240 panel?


Quote:
Originally Posted by tbeaulieu View Post
After digging around in the barn last night, I believe I was mistaken in the assumption that I "have 240" in the barn.
You probably DO have "240" in the barn. You just don't have any 240 Volt branch circuits wired out there.

Quote:
I'm interpretting what I see as:

240 comes in from the house.

These two hot lines are used to supply four 14 AMP circuits.

Does this sound right, given the photos?
It appears that your box has four 20 Amp circuits, with one dead circuit ( fuse missing)

Quote:
If so, does this mean I'm stuck? I assume I'd need to run additional lines in from the main box if I wanted 240 in the barn.
Not really. Depending on what those other 20 Amp circuits are for, and how much load you have, you could possibly combine them together into 2 circuits, freeing up 2 spaces for your power saw circuit.

While it is in your best interest in the long run to replace those fuse boxes with a suitable breaker box, and install a heavier feeder cable from your house, there is probably sufficient capacity to at least test run your saw with your existing box.
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Old 03-03-2010, 09:01 PM   #12
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How can I evaluate my 120/240 panel?


So I did some more snooping tonight. The line from the main box is indeed 10 gauge x 3. It's hanging off two small breakers that are ganged together with a rod, so that they work together. Each one is 40 AMPS. Does that mean the line is 80 AMPS to the barn? Does 10 gauge allow for 80 AMPS?

Oh, and the missing fuse was my doing ... it took me a few minutes to figure out that reason my shallow well pump blew that fuse was because it had frozen and split open like a mellon!

I find it interesting the first box has two 60AMP fuses and then feeds the panel, which has two more 60 AMP fuses (in that black pullout unit in the left receptacle). Seems strange to me.

It seems to me that this is now entirely possible to shuffle things around a bit. I have next to nothing consuming power out there now, but I'm trying to plan some shop tools, including dust collection, so it would be nice to come up with a layout that's safe, legal and practical.
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Old 03-03-2010, 09:03 PM   #13
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How can I evaluate my 120/240 panel?


10g is only good for 30a, so you have 30a @240v

The 40a breaker needs to be swapped for a 30a
You can overload that the #10 wire

The 60a setup is merely a shut-off
Since the main panel breaker controls how much power is delivered
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Old 03-22-2010, 01:01 PM   #14
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How can I evaluate my 120/240 panel?


Hi Dave.

I want to start putting together the plan for the 240v rewire.

The idea is to run some new, bigger wire to the barn. In theory, I could leave the existing power as-is and wire the 240v stuff seperately. I believe there's a requirement of a single shut-off point, so the idea came to me that I could replace the existing 40A double breaker with something larger and feed a sub panel near my main panel that would have the existing 10# line and the new 6# line both connected to it. I assume the circuit breaker qualifies as a switch. If not, I assume a switch could be added to the sub panel.

I'm trying to get an electrician to help with the project, but wanted to get started with some homework. I'd love to be able to do most of the grunt work myself and let him do the consulting and final hookup.

I'm thinking of having 3-4 240v 30A outlets. I'd expect to only be using 2 at any one time (dust and saw). And I'd leave the existing 4 20A circuits. The saw is 15A. The dust collector is 2HP.

The distance to the barn is approximately 75 feet.
The existing 10# is entirely inside. It runs through the floor, into the mudroom, along the roof, through the inside wall of the connected barn, up timbers and down a post.

What are your thoughts on the best way to proceed? I know there are a lot of concepts in the mix, so it's not 100%.

Can I just run a new line along side it? Or is that no longer allowed?
Should I abandon the existing 10# and run everything over a single 6#?
Or, even a 4#?

Thanks again for the help, dave!
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Old 03-22-2010, 01:23 PM   #15
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How can I evaluate my 120/240 panel?


You can only have one power feed to a seperate building
You might be able to pull the existing wire back & use it on a post seperate from the building
But probably more trouble then its worth
Since its #10 the 40a breaker needs to be replaced with a 30a
But it seems the building is attached ?

Its run along the roof ? Inside or outside ?
My only fear with older wire is that...its older
If its in good shape I'd use it if its a 4 wire feed
It looks like newer 10-3 w/ground feeds this
I'd pull out the fuses & replace with a small sub I think

#6 would work for 60a 240v sub
I use a 100a main breaker panel & feed it with 60a

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