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Old 02-24-2010, 04:33 PM   #1
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What is a multlwire circuit? Same thing as a duplex breaker circuit?
what size copper wire would I run for a `100 amp subpanel?
Is there a link for different subpanel applications?
In a 200 amp main does that mean that you have 24,000 watts available at all times 120vac X 200 amps or is it 240 X 200 amps equal 48,000?

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Old 02-24-2010, 04:50 PM   #2
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what does POCO stand for?

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Old 02-24-2010, 04:57 PM   #3
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POCO stands for power company.
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Old 02-24-2010, 05:18 PM   #4
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You might be thinking of a Multiwire Branch Circuit. I believe this is two circuits that each have their own Hots, but share a Neutral.
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Old 02-24-2010, 05:35 PM   #5
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Originally Posted by Livewire78 View Post
What is a multlwire circuit? Same thing as a duplex breaker circuit?
what size copper wire would I run for a `100 amp subpanel?
Is there a link for different subpanel applications?
In a 200 amp main does that mean that you have 24,000 watts available at all times 120vac X 200 amps or is it 240 X 200 amps equal 48,000?
A few random answers Blue..maybe.....No

Multiwire as said is 2 circuits that share a neutral with each hot leg pulling power from different hot bus

Size wire depends upon distance, specific wire & other factors

Different sub-panel applications ??
Every sub-panel is used to distribute power

200a is 200a on each leg
If either leg exceeds 200a the breaker trips
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Old 02-24-2010, 06:46 PM   #6
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For determining the number of watts "available"... what are you trying to figure out? Watts are only in effect when there is a load, not when there is a potential for load. The amount of watts consumed by a load at the circuit voltage is what determines the amps pulled through the breaker(s). Theoretically though, yes you could pull approx. 24 kW on a 120V circuit with a 200A breaker OR 48 kW on a 240V circuit with a 200A breaker. Since the voltage is different, both would result in comparable amperage.

This is based on my basic understanding of electricity. If I'm glaringly wrong somewhere someone please correct me, too!
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Old 02-24-2010, 06:57 PM   #7
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For determining the number of watts "available"... what are you trying to figure out? Watts are only in effect when there is a load, not when there is a potential for load. The amount of watts consumed by a load at the circuit voltage is what determines the amps pulled through the breaker(s). Theoretically though, yes you could pull approx. 24 kW on a 120V circuit with a 200A breaker OR 48 kW on a 240V circuit with a 200A breaker. Since the voltage is different, both would result in comparable amperage.

This is based on my basic understanding of electricity. If I'm glaringly wrong somewhere someone please correct me, too!
I was just wondering if, in theory if I maxed out a 200 amp service how many watts could be consumed
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Old 02-24-2010, 07:03 PM   #8
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I guess the reason I ask is I'm curious what size battery bank I need to build to make it equal @ 48vdc X 500 AH = 24000 watts
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Old 02-25-2010, 06:51 PM   #9
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generally you should not exceed 80% of the rated full load of a breaker...for instance a 15 amp breaker shouldn't be loaded more than 1440 watts...15 A x 120 V * 0.8 = 1440 watts

Do you mean you have a 100 amp breaker for each leg? Each leg is 120 volts and 180 degrees out of phase...so if you connect both hots together you get your 240 nominal. Your total wattage with both legs combined shouldn't be more than 19200 watts
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Old 02-25-2010, 07:01 PM   #10
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generally you should not exceed 80% of the rated full load of a breaker...for instance a 15 amp breaker shouldn't be loaded more than 1440 watts...15 A x 120 V * 0.8 = 1440 watts

Do you mean you have a 100 amp breaker for each leg? Each leg is 120 volts and 180 degrees out of phase...so if you connect both hots together you get your 240 nominal. Your total wattage with both legs combined shouldn't be more than 19200 watts
Thankyou so much!!! Do you know if there is a link for running wires to different size subpanels.
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Old 02-25-2010, 08:46 PM   #11
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generally you should not exceed 80% of the rated full load of a breaker...for instance a 15 amp breaker shouldn't be loaded more than 1440 watts...15 A x 120 V * 0.8 = 1440 watts
This is false, breakers are rated to run at 100% capacity
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Old 02-26-2010, 01:06 AM   #12
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This is false, breakers are rated to run at 100% capacity
Sure, a breaker is rated to run at 100% capacity, but doesn't the NEC dictate that a circuit be designed to not exceed 80% of rated capacity?
http://ecmweb.com/mag/electric_sizing_circuit_breaker/
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Old 02-26-2010, 06:33 AM   #13
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Sure, a breaker is rated to run at 100% capacity, but doesn't the NEC dictate that a circuit be designed to not exceed 80% of rated capacity?
http://ecmweb.com/mag/electric_sizing_circuit_breaker/
Only on loads designed to run more than 3 hours at a time!
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Old 02-26-2010, 08:29 AM   #14
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Only on loads designed to run more than 3 hours at a time!
Ok, now that makes sense.

To use a car metaphore, when I first read the comments, it seemed like joseph was simply saying that the speed limit is 70mph, but dave was pointing out the car was designed to go 120mph.

But now I understand that you're not really speeding unless you do so continuously for 3 hours.
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Old 02-26-2010, 08:39 AM   #15
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Of course you could run the breaker at 100% capacity but think about the consequences...if your running at 100% capacity how much margin do you have before the breaker will trip on an overcurrent? The answer is close to none...thats why the "general rule" for CONTINUOUS LOADS is to not load the breaker more than 80% so your not tripping your breakers constantly

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