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Old 10-14-2012, 11:32 PM   #1
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Circuit breaker circuitry


Alright iv been googling and madly scratching my head and everything. I get how the 2 different phases work and how circuit breaker works and everything. But i just cant figure how this whole amp thing works amongst it.

Example as i was trying to figure out in another thread was that the shed im trying to put a new elec system in has 2 different circuit breakers. One 15A breaker is on phase A and the other 15A breaker is on phase B which they both use black and white wire which equals out to 240V's. And then in the shed it uses the ground wire as a neutral to bring it down to 120V. Apparently this doesnt equal out 30A of power and only equals out at 15A's. Then in the shed Black goes to 1 15A breaker and White goes to another 15A breaker and those both as i said use the ground as neutral. Which from my mad googling has not turned up nothing at all. If someone can explain id be extremly happy. and if someone can understand what im saying.


Last edited by mattintc; 10-14-2012 at 11:36 PM.
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Old 10-15-2012, 06:53 AM   #2
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Circuit breaker circuitry


Check out this thread.

Barn Connection
Check post #8 and thanks to stubbie, you should get a better understanding.

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Old 10-15-2012, 08:07 AM   #3
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Circuit breaker circuitry


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Originally Posted by mattintc View Post
Example as i was trying to figure out in another thread was that the shed im trying to put a new elec system in has 2 different circuit breakers. One 15A breaker is on phase A and the other 15A breaker is on phase B which they both use black and white wire which equals out to 240V's. And then in the shed it uses the ground wire as a neutral to bring it down to 120V. Apparently this doesnt equal out 30A of power and only equals out at 15A's. Then in the shed Black goes to 1 15A breaker and White goes to another 15A breaker and those both as i said use the ground as neutral..
Caution, you may not use ground as the neutral.

For 120 volt power you would either have to run just one "phase" out there with black as hot and white as neutral, or you would have to replace the cable with a cable with 3 wires (typically red and black, plus the required white) plus ground.

You are allowed to use both black and white for the two hots in a 240 volt only circuit.

With a double 15 amp breaker (very old installations might have 2 single breakers) to which the red and black are connected with 240 volts between them, plus the white neutral, you do get up to 30 amps of 120 volts altogether split 15/15. However if you draw, say, just 7 amps from the red side (red phase if you insist) you may not draw 23 amps from the black side to equal 30. If you had a 240 volt receptacle and had no 120 volt lights or appliances turned on you could draw up to 15 amps at 240 volts.
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Last edited by AllanJ; 10-15-2012 at 08:18 AM.
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Old 10-15-2012, 09:47 AM   #4
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Circuit breaker circuitry


This is a pretty "in-depth" subject. A lot of electrical terms are used to explain this, so you need to also learn about each term to understand explanations of how this works. (Like "transformer". Understand what the word transformer means, how those work, then you will understand more about a "neutral". But to learn about transformers, you need to learn about the word "inductance"! Seems like learning about this will be a never ending process. But just keep reading and learning. Look up each word/term you do not understand.

Here is a start...
(Homes use "single phase" electricity, not 3 phase which businesses/industry uses.)
http://en.wikipedia.org/wiki/Split-phase_electric_power
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Old 10-15-2012, 01:40 PM   #5
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Circuit breaker circuitry


thank you all that was EXTREMLY helpful!! Now i can see how you can go about using a 2 pole tandem breaker!
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Old 10-15-2012, 01:42 PM   #6
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Circuit breaker circuitry


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Originally Posted by jbfan View Post
Check out this thread.

Barn Connection
Check post #8 and thanks to stubbie, you should get a better understanding.
THANK YOU i wish someone showed me that sooner that is amazing!
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Old 10-15-2012, 01:47 PM   #7
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Circuit breaker circuitry


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Caution, you may not use ground as the neutral.

For 120 volt power you would either have to run just one "phase" out there with black as hot and white as neutral, or you would have to replace the cable with a cable with 3 wires (typically red and black, plus the required white) plus ground.

You are allowed to use both black and white for the two hots in a 240 volt only circuit.

With a double 15 amp breaker (very old installations might have 2 single breakers) to which the red and black are connected with 240 volts between them, plus the white neutral, you do get up to 30 amps of 120 volts altogether split 15/15. However if you draw, say, just 7 amps from the red side (red phase if you insist) you may not draw 23 amps from the black side to equal 30. If you had a 240 volt receptacle and had no 120 volt lights or appliances turned on you could draw up to 15 amps at 240 volts.

Oh so it works exactly as i had thought. Someone thought i was full of it and told me that a double pole 30A breaker dont equal out to 60A of power. Thank you for clarifying that! And this system is about roughly 35 years old that is in our house....

Last edited by mattintc; 10-15-2012 at 01:53 PM.
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Old 10-15-2012, 01:50 PM   #8
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Circuit breaker circuitry


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Originally Posted by Billy_Bob View Post
This is a pretty "in-depth" subject. A lot of electrical terms are used to explain this, so you need to also learn about each term to understand explanations of how this works. (Like "transformer". Understand what the word transformer means, how those work, then you will understand more about a "neutral". But to learn about transformers, you need to learn about the word "inductance"! Seems like learning about this will be a never ending process. But just keep reading and learning. Look up each word/term you do not understand.

Here is a start...
(Homes use "single phase" electricity, not 3 phase which businesses/industry uses.)
http://en.wikipedia.org/wiki/Split-phase_electric_power
I know what inductance means and transformer and all that stuff. That was learned in my automotive electrical class and before that. i got started in both home electrical and automotive electrical when i was 16 or younger BUT i am going to read through this.
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Old 10-15-2012, 02:11 PM   #9
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Circuit breaker circuitry


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Oh so it works exactly as i had thought. Someone thought i was full of it and told me that a double pole 30A breaker dont equal out to 60A of power. Thank you for clarifying that! And this system is about roughly 35 years old that is in our house....
Thats because it dosen't
A 30 amp double pole breaker only allows 30 amps per pole before tripping.
It does not add up to 60 amps!

A tandem breaker is not a 2 pole breaker, and you stand the chance to overload the neutral wire if you use it as such!
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Last edited by jbfan; 10-15-2012 at 05:47 PM.
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Old 10-15-2012, 02:23 PM   #10
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Circuit breaker circuitry


Judging by the comment about the system being 35 years old in the house, I think he's referring to the current two single pole 15A breakers feeding his shed. To further clarify, you don't have 30A here either -- while you can pull a total of 30A within your shed it still has to be less than 15A on each side. As AllanJ pointed out, you couldn't pull 7A on one leg and 23A on the other.
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Old 10-15-2012, 03:33 PM   #11
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Circuit breaker circuitry


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Thats because it dosen't
A double pole breaker only allows 30 amps per pole before tripping.
It does not add up to 60 amps!

A tandem breaker is not a 2 pole breaker, and you stand the chance to overload the neutral wire if you use it as such!
AHHHH i see! ok im getting it. im sorry for being so hard headed and im glad your patient.

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