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Old 03-21-2008, 08:54 PM   #1
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What if?


This is strictly hypothetical. I have not done this, not do I plan on it, nor do I suggest anyone else do it. I just want to know to satisfy my own curiousity.


What would happen if you tried to hook up a 240V appliance by taking 1 wire, say 4AWG, and dividing the strands in half then hooking each half to each leg of a double pole breaker, then same at recep?



Also, what would happen if you took a single pole breaker and fed it to another single pole breaker?




This is strictly hypothetical. I have not done this, not do I plan on it, nor do I suggest anyone else do it. I just want to know to satisfy my own curiousity.

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Old 03-21-2008, 08:56 PM   #2
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What if?


Come on Cowboy. Please tell me this is not a serious question.

Sorry, I see you edited. I am referring to the first question.

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Old 03-21-2008, 08:57 PM   #3
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What if?


Inquiring minds want to learn!
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Old 03-21-2008, 09:05 PM   #4
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What if?


Think about it. After you separate the strands of the conductor, where do they go?
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Old 03-21-2008, 09:06 PM   #5
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What if?


Andy, I know you know the answer to #1.

As for question #2, it depends on what phases the breakers are on. If they are on the same phase, nothing will happen. It will be what we call "double fed". If different phases, see answer #1
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Old 03-21-2008, 09:09 PM   #6
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Quote:
Originally Posted by Speedy Petey View Post
Think about it. After you separate the strands of the conductor, where do they go?
To each terminal of a double pole breaker.
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Old 03-21-2008, 09:11 PM   #7
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What if?


And then back together into the same conductor.

Dead short, no?
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Old 03-21-2008, 09:15 PM   #8
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Quote:
Originally Posted by Speedy Petey View Post
And then back together into the same conductor.

Dead short, no?
i am not a licensed electrician, but I did stay at a Holiday Inn last night!
Just had to say that. But seriouse, I had to get certified in trash compactor repairs in Easly SC. When we went to the class one of the subjects they tought us was to be verry carefull not to cause a phase to phase short. Mmm, I just could not imagine
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Old 03-21-2008, 09:26 PM   #9
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i am not a licensed electrician, but I did stay at a Holiday Inn last night!
Just had to say that. But seriouse, I had to get certified in trash compactor repairs in Easly SC. When we went to the class one of the subjects they tought us was to be verry carefull not to cause a phase to phase short. Mmm, I just could not imagine
Yes those are particularly nasty, but only because of the change in voltage. Energy available in the short goes up by the SQUARE of the change in voltage. So, a 120 V line-to-ground short has X amount of explosive energy. But 240 is twice the voltage, so the available energy in a 240 V short is 4 times a 120 V short. A 480 V short has 16 times the explosive energy of a 120 V short at only 4 times the voltage. It gets bad quick.

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Old 03-21-2008, 09:29 PM   #10
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What if?


You already know what would happen. It would be the same as taking each end of the wire and attaching it to each pole of a double pole breaker.

As for the second question, current only flows when there is a difference in potential. If the breakers are on the same phase, there is no difference in potential. If on different phases...

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Old 03-21-2008, 09:31 PM   #11
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What if?


So basiclly if they were on the same phase... nothing

if they were on different phases... sparks and noise and lots of bad stuff?
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Old 03-21-2008, 09:35 PM   #12
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So basiclly if they were on the same phase... nothing

if they were on different phases... sparks and noise and lots of bad stuff?
Well, maybe, maybe not. If the wire is connected to each breaker, and the breakers are connected solidly to the bus, then you just get a violent throw of the breaker handles. You may see sparks from inside the breaker. I have seen breakers shatter on high voltage systems. 480 V.

We call this "bucking phases"

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Old 03-21-2008, 10:13 PM   #13
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What if?


Quote:
So basiclly if they were on the same phase... nothing

if they were on different phases... sparks and noise and lots of bad stuff?

Yeah..............pretty much.


Ya gotta keep em separated.
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Old 03-22-2008, 02:50 PM   #14
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If the breakers are on different "phases", they could both trip, or one or the other might trip, leaving the other untripped. Or, both breakers could disintegrate, although I highly doubt a breaker would ever destroy itself if the voltage is with it's rating. They are designed to take huge amounts of short-circuit current.

Another thing that could happen, is there could be a very short but incredibly high surge current drawn from your local distribution system, causing a chain-reaction and finally resulting in the failure of the entire grid, leaving millions of customers without power!
I think they call that the butterfly effect.

When I was a kid, I didn't understand how the 3-way lamp switches worked. There is one position where both filaments light, thus all of the contacts of the switch are connected together.

I had this switch set up so that I could switch a lamp from getting it's power from one receptacle or another in the room.
When I switched the switch to the position where all contacts were connected, the switch blew itself up, and I blew two fuses, one on each side of the 3-wire service.
I had 240 volts across the switch, and it is almost a miracle that I wasn't shocked, or didn't start a fire!

I did a lot of really boneheaded things as a child, before understanding electricity and it's distribution.
But perhaps I knew a lot more than I thought I did, as I was rarely shocked, and never started a fire.
I did blow fuses from time to time though<g>

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Old 03-22-2008, 03:49 PM   #15
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Quote:
Originally Posted by InPhase277 View Post
Yes those are particularly nasty, but only because of the change in voltage. Energy available in the short goes up by the SQUARE of the change in voltage. So, a 120 V line-to-ground short has X amount of explosive energy. But 240 is twice the voltage, so the available energy in a 240 V short is 4 times a 120 V short. A 480 V short has 16 times the explosive energy of a 120 V short at only 4 times the voltage. It gets bad quick.

InPhase277
And to think, some of those trash compactors run on 660 volt. Big Boom huh?

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