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Old 02-06-2011, 04:56 PM   #1
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240 volt breaker question


I recently rewired my garage and ran one 240 volt line of 10-3 from a thirty amp breaker. Now that I am installing all my new tools I end up needing two 20 amp outlets, but the tools actually only use 9 amps each. Is it safe to run both 20 amp outlets off of the 30 amp breaker, or should I change the breaker to a 20 amp?

Thanks in advance.

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Old 02-06-2011, 05:00 PM   #2
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240 volt breaker question


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Originally Posted by Chet Douglas View Post
I recently rewired my garage and ran one 240 volt line of 10-3 from a thirty amp breaker. Now that I am installing all my new tools I end up needing two 20 amp outlets, but the tools actually only use 9 amps each. Is it safe to run both 20 amp outlets off of the 30 amp breaker, or should I change the breaker to a 20 amp?

Thanks in advance.
Change it to a 20amp breaker

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Old 02-06-2011, 05:07 PM   #3
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240 volt breaker question


If you install 120 receptacles you will not have 240 available in your garage.

Using a 2 pole 20 amp breaker you can have 2 - 20amp 120 Volt circuits using a Multiwire Branch Circuit (MWBC), but you can not use it for 240.
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Old 02-06-2011, 05:09 PM   #4
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240 volt breaker question


Thanks for the quick response!

Just to clarify something here I want to be able to use both tools at once, can I run two 20 amp outlets off the line and use both 9 amp tools on a 20 amp breaker? Thanks again.
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Old 02-06-2011, 05:12 PM   #5
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240 volt breaker question


With a MWBC, you can have each receptacle on its own circuit.

If they were on the same 20 amp circuit, you might trip a breaker if both tools started at the same time.
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Old 02-06-2011, 05:13 PM   #6
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240 volt breaker question


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Originally Posted by Chet Douglas View Post
Thanks for the quick response!

Just to clarify something here I want to be able to use both tools at once, can I run two 20 amp outlets off the line and use both 9 amp tools on a 20 amp breaker? Thanks again.
Yes, If you change to a twenty amp breaker, you could have 2 separate 20 amp circuits sharing a natural. So yes you could as long as they are 120volt tools, as stated above you will not have a 240 circuit anymore if you put in 120volt receptacles.
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Old 02-06-2011, 05:20 PM   #7
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240 volt breaker question


Sorry, I guess I wasn't clear. Both tools are 240 volt and have 20 amp plugs. They operate at 9 amps each. With both tools the total amperage will be 18 amps, is it possible to split the 240 volt outlet to operate both at once, and if so what size breaker should I use.

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Old 02-06-2011, 05:23 PM   #8
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240 volt breaker question


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Sorry, I guess I wasn't clear. Both tools are 240 volt and have 20 amp plugs. They operate at 9 amps each. With both tools the total amperage will be 18 amps, is it possible to split the 240 volt outlet to operate both at once, and if so what size breaker should I use.

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Ok, yes you can put in a 240 20 circuit and should be able to use both tools. You will be close to maxing it out tho. If you were to fire both up at the same time you could trip the breaker tho! You will also need 240 volt 20 amp receptacles, not reg receptacles!
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Old 02-06-2011, 05:32 PM   #9
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240 volt breaker question


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Originally Posted by Chet Douglas View Post
Both tools are 240 volt and have 20 amp plugs. They operate at 9 amps each. With both tools the total amperage will be 18 amps, is it possible to split the 240 volt outlet to operate both at once, and if so what size breaker should I use.
You said you ran 10/3 to your garage. How did you terminate this run? What did you do with the white neutral? 10/3 is typically good for 30 amps.
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Old 02-06-2011, 05:36 PM   #10
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240 volt breaker question


Thanks, can I run two receptacles off of the single 10-3 line? The wires are all already run and drywall installed, mud and taped and painted. Would it be better to use a 30 amp breaker to prevent possible startup tripping?
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Old 02-06-2011, 05:37 PM   #11
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240 volt breaker question


I know... I just didn't use the neutral, but wanted to be prepared for if it was needed.
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Old 02-06-2011, 05:41 PM   #12
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240 volt breaker question


This is the whole problem. I initially thought I would need a 30 amp breaker, but after I finished the garage and purchased all the tools and toys for my new workshop I realized that instead of needing a single 30 amp outlet, I have two tools that run off of 240v 20amp cords at 9 amps each.
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Old 02-06-2011, 05:43 PM   #13
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240 volt breaker question


You said in the original post you ren a 240 volt line off a 30 amp breaker, that has to be a 2pole 240 volt breaker or you did not have a 240 volt circuit.

You can not connect 20 amp general purpose receptacles to a circuit fused at 30 amps
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Old 02-06-2011, 05:50 PM   #14
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240 volt breaker question


Do you already have two 240volt outlets installed and connected? The 30 amp breaker you installed in your panel to support this is sized to protect the the #10 wire. Each 20 amp receptacle will allow you to plug in a 20 amp plug. It doesn't mean you will be pulling 20 amps but you could if the tool required it. Since your tools are 9 amps with a total of 18 amps, you are well below 30 amps.
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Old 02-06-2011, 05:51 PM   #15
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240 volt breaker question


The receptacles are 20 amp 240v.

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