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Old 09-09-2008, 03:58 PM   #1
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Understanding how to size a circuit conductor


Let's say I have a device, a time machine perhaps, that I will be hard wiring into my panel with it's own breaker. On the label, next to where it says "1.21 gigawatts", it says that minimum ampacity is 52 amps and maximum circuit breaker size is 60 amps.

Per the NEC, which of those numbers (beside 1.21 gigwatts ) should I use to determine conductor gauge, and why?

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Old 09-09-2008, 04:03 PM   #2
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Understanding how to size a circuit conductor


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Originally Posted by gp_wa View Post
Let's say I have a device, a time machine perhaps, that I will be hard wiring into my panel with it's own breaker. On the label, next to where it says "1.21 gigawatts", it says that minimum ampacity is 52 amps and maximum circuit breaker size is 60 amps.

Per the NEC, which of those numbers (beside 1.21 gigwatts ) should I use to determine conductor gauge, and why?

Is this really just an AC unit?

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Old 09-09-2008, 04:16 PM   #3
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Understanding how to size a circuit conductor


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Originally Posted by chris75 View Post
Is this really just an AC unit?
No it's a time machine :D


I'm trying to keep it general by not actually telling you what it is. If it matters, then I'm hoping that will just be part of the answer.
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Old 09-09-2008, 06:10 PM   #4
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Understanding how to size a circuit conductor


Quote:
Originally Posted by gp_wa View Post
Let's say I have a device, a time machine perhaps, that I will be hard wiring into my panel with it's own breaker. On the label, next to where it says "1.21 gigawatts", it says that minimum ampacity is 52 amps and maximum circuit breaker size is 60 amps.
Per the NEC, which of those numbers (beside 1.21 gigwatts ) should I use to determine conductor gauge, and why?
I suppose it would depend on the vertical rebound index of the flux capacitor, wouldn't it ???

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Old 09-09-2008, 06:28 PM   #5
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Understanding how to size a circuit conductor


Circuit/breaker sizes go from 50 to 60 amps.

52 is greater than 50 so do the math. #6


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Old 09-09-2008, 06:39 PM   #6
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Understanding how to size a circuit conductor


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Circuit/breaker sizes go from 50 to 60 amps.

52 is greater than 50 so do the math. #6
Do the math on which number? 52 or 60?
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Old 09-09-2008, 07:06 PM   #7
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Understanding how to size a circuit conductor


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I suppose it would depend on the vertical rebound index of the flux capacitor, wouldn't it ???
No, this is a newer model, well actually an older model, it gets confusing with these things. Anyway, they switched to a linear dual axis rebound index after (I mean before) some guy got turned into a newt. It'll be in the news twelve years ago.
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Old 09-09-2008, 08:01 PM   #8
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Understanding how to size a circuit conductor


Use awg #6 fused at 60 amps
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Old 09-09-2008, 08:04 PM   #9
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Understanding how to size a circuit conductor


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Do the math on which number? 52 or 60?

Edited:
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Circuit/breaker sizes go directly from 50 to 60 amps
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Old 09-09-2008, 08:18 PM   #10
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Understanding how to size a circuit conductor


It certainly DOES matter what it is. A/C's, motors and welders all have dedicated sections in the code and follow certain rules. Time machines do not have this luxury.
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Old 09-09-2008, 09:18 PM   #11
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Understanding how to size a circuit conductor


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Originally Posted by 220/221 View Post
Edited:
You're missing my question. I am asking which number is of relevance to this calculation, 52 (minimum ampacity), or 60 (maximum protection).

I understand why you'd use a 60 amp breaker as apposed to a 52 amp one...
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Old 09-09-2008, 09:21 PM   #12
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It certainly DOES matter what it is. A/C's, motors and welders all have dedicated sections in the code and follow certain rules. Time machines do not have this luxury.
If it has a motor, does that have a bearing on which of the two numbers I've asked about are relevant?

I thought that the difference was between continuous and intermittent rating, and that a continuous rating changes the wire gauge needed for a particular amp rating.

In other words, a heat coil drawing 50 amps might require #6 wire, while a motor drawing 50 amps might require #5.
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Old 09-09-2008, 09:30 PM   #13
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Understanding how to size a circuit conductor


In your case, 52MCA & 60 Max OCPD, the answer is still 60A and #6.
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Old 09-09-2008, 09:32 PM   #14
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In your case, 52MCA & 60 Max OCPD, the answer is still 60A and #6.
My case, assuming what? (sorry) A/C, motor, welder, none of the above?
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Old 09-09-2008, 09:40 PM   #15
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Understanding how to size a circuit conductor


If your time machines factory nameplate says minimum ampacity 52 amps then you need to size the conductor based on that amperage. Which would be a #6 awg copper conductor or one with a higher ampacity. The max breaker is just that 60 amps maximum. You can't use a 50 because it is not sufficient for the load served. As said several times there is not a 55 amp breaker so next protection size after 52 amps is 60. Motors are 1.25 times the largest plus the sum of the rest, if a single motor then 1.25 times the flc of that motor. If the equipment is a continuous load (will be operating for 3 hours or more) then it is 1.25 times the rated ampacity of that equipment. If however a nameplate states minimum ampacity then continuous or whatever has already been factored in and the equipment must be served with conductors that have at least that minimum ampacity.

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