# Branch circuit rating defined by wire or breaker?



## backstay (Feb 3, 2011)

swimmer said:


> *210.3 Rating.* Branch circuits recognized by this article shall be rated in accordance with the maximum permitted ampere rating or setting of the overcurrent device.
> 
> So if I have a 15A breaker protecting 30 AWG wire, then I have a 30A circuit because a 30A breaker is permitted even though I'm using a 15A breaker?


Why would you?


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## Awg-Dawg (Jan 23, 2007)

backstay said:


> Why would you?


Voltage drop is one reason.

Besides that, I assume it is a hypothetical question.


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## bkmichael65 (Mar 25, 2013)

If you have a 15 amp breaker, you have a 15 amp circuit.


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## Roger (Jul 7, 2007)

bkmichael65 said:


> If you have a 15 amp breaker, you have a 15 amp circuit.


Or a 30 amp circuit that trips at around 15 amps. 

Roger


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## backstay (Feb 3, 2011)

Awg-Dawg said:


> Voltage drop is one reason.
> 
> Besides that, I assume it is a hypothetical question.


 But I would think you would still have a 15 amp circuit, with VD to be part of the picture.


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## Hack Work (Dec 29, 2013)

swimmer said:


> *210.3 Rating.* Branch circuits recognized by this article shall be rated in accordance with* the maximum permitted ampere rating or setting of the overcurrent device*.
> 
> So if I have a 15A breaker protecting 30 AWG wire, then I have a 30A circuit because a 30A breaker is permitted even though I'm using a 15A breaker?


The "_the maximum permitted ampere rating or setting of the overcurrent device_" is 15A so it's a 15A circuit.


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## Dennis Alwon (May 9, 2009)

I think his point is that if an HVAC units allows a max 30 amp circuit but you use a 25 amp overcurrent protective device then the circuit is rated 25 amps but the definition states max permitted. So if I use a 25 amp overcurrent protective device and the max is 30 amps does that mean I have a 30 amp circuit? No but by that definition it could mean exactly that.


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## FlyingSparks (Dec 10, 2012)

swimmer said:


> *210.3 Rating.* Branch circuits recognized by this article shall be rated in accordance with the maximum permitted ampere rating or setting of the overcurrent device.
> 
> So if I have a 15A breaker protecting 30 AWG wire, then I have a 30A circuit because a 30A breaker is permitted even though I'm using a 15A breaker?


30awg wire? WHAT?


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## HARRY304E (Sep 15, 2010)

FlyingSparks said:


> 30awg wire? WHAT?


He just means 30 amps.


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## BBQ (Nov 16, 2010)

Dennis Alwon said:


> I think his point is that if an HVAC units allows a max 30 amp circuit but you use a 25 amp overcurrent protective device then the circuit is rated 25 amps but the definition states max permitted. So if I use a 25 amp overcurrent protective device and the max is 30 amps does that mean I have a 30 amp circuit? No but by that definition it could mean exactly that.



If you have 12 AWG on a 30 amp breaker in a code compliant way you do in fact have a 30 amp circuit.


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## Dennis Alwon (May 9, 2009)

BBQ said:


> If you have 12 AWG on a 30 amp breaker in a code compliant way you do in fact have a 30 amp circuit.


Yes I know that but I didn't say that. I was saying if I had 10 wire on a 25 amp breaker but the HVAC unit allows a max 30 amp by the definition it would be a 30 amp cir. since the max allowable would be a 30 amp overcurrent protective device. That does not make sense.


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## Deep Cover (Dec 8, 2012)

swimmer said:


> *210.3 Rating.* Branch circuits recognized by this article shall be rated in accordance with the maximum permitted ampere rating or setting of the overcurrent device.





Dennis Alwon said:


> Yes I know that but I didn't say that. I was saying if I had 10 wire on a 25 amp breaker but the HVAC unit allows a max 30 amp by the definition it would be a 30 amp cir. since the max allowable would be a 30 amp overcurrent protective device. That does not make sense.


I don't think you are correct because the HVAC unit is not the overcurrent device. The breaker is, which would make that circuit a 25A circuit.


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## Deep Cover (Dec 8, 2012)

I'll throw a screwball at you guys...

480V 3P HVAC Min cir 20A Max OCP 35A

50A breaker feeding #12's to a disconnect fused at 35A...what size circuit?


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## Dennis Alwon (May 9, 2009)

Deep Cover said:


> I don't think you are correct because the HVAC unit is not the overcurrent device. The breaker is, which would make that circuit a 25A circuit.


Look at the art. quoted. It says "the maximum permitted ampere rating or setting of the overcurrent device". It does not say the setting of the actual device-- IMO that is what it means but not what it states. Well it does not say it clearly I can interpret it either way


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## Deep Cover (Dec 8, 2012)

Dennis Alwon said:


> Look at the art. quoted. It says "the maximum permitted ampere rating or setting of the overcurrent device". It does not say the setting of the actual device-- IMO that is what it means but not what it states


It's exactly what it states...

The max permitted ampere rating of the overcurrent device or setting of the overcurrent device. The overcurrent device isn't the HVAC unit, it is the breaker.


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## Dennis Alwon (May 9, 2009)

Deep Cover said:


> It's exactly what it states...
> 
> The max permitted ampere rating of the overcurrent device or setting of the overcurrent device. The overcurrent device isn't the HVAC unit, it is the breaker.


I understand what it says I just think it could be clearer. It almost feels like since the maximum permitted amperage of the overcurrent protective device can be 30 then it is 30 amps. What it is in fact trying to say is the max. overcurrent protective device or setting of that overcurrent protective device that is in place. I just think others may be confused but I do know what is meant by it


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## BBQ (Nov 16, 2010)

Dennis Alwon said:


> Yes I know that but I didn't say that. I was saying if I had 10 wire on a 25 amp breaker but the HVAC unit allows a max 30 amp by the definition it would be a 30 amp cir. since the max allowable would be a 30 amp overcurrent protective device. That does not make sense.


I disagree with that completely.

The rating / listing / labeling of the HVAC has nothing to do with the NEC rating of the branch circuit.

(I mean, we have to make sure the rating of the circuit meets the labeling but the labeling does not define the rating of the circuit.)


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## BBQ (Nov 16, 2010)

Deep Cover said:


> I'll throw a screwball at you guys...
> 
> 480V 3P HVAC Min cir 20A Max OCP 35A
> 
> 50A breaker feeding #12's to a disconnect fused at 35A...what size circuit?


With a fused disconnect at the unit you have a violation.

From the 50 amp to the fused disconnect is a feeder and would require 50 amp rated conductors.

From the fused disconnect to the unit would be a 35 amp branch circuit and could use the 12 AWGs.


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## BBQ (Nov 16, 2010)

Dennis Alwon said:


> Look at the art. quoted. It says "the maximum permitted ampere rating or setting of the overcurrent device". It does not say the setting of the actual device-- IMO that is what it means but not what it states. Well it does not say it clearly I can interpret it either way


OK, you suck. :laughing:

Now you got me thinking on this. Damn Charlies rule.:laughing:


I thought it was clear now I find it unclear. :blink:


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## MTW (Aug 28, 2013)

BBQ said:


> OK, you suck. :laughing:
> 
> Now you got me thinking on this. Damn Charlies rule.:laughing:
> 
> ...


Mark this down. BBQ was wrong about a code article. :whistling2::thumbup:


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## Dennis Alwon (May 9, 2009)

BBQ said:


> OK, you suck. :laughing:
> 
> Now you got me thinking on this. Damn Charlies rule.:laughing:
> 
> ...


I think what is clear is the intent but I am convinced the wording could be better .


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## BBQ (Nov 16, 2010)

Deep Cover said:


> It's exactly what it states...
> 
> The max permitted ampere rating of the overcurrent device or setting of the overcurrent device. The overcurrent device isn't the HVAC unit, it is the breaker.


Is it clear?



> _the maximum permitted_ ampere rating or setting of the overcurrent device.


It says maximum permitted, not the maximum installed. :blink:


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## BBQ (Nov 16, 2010)

MTW said:


> Mark this down. BBQ was wrong about a code article.


Whoa!!!

Lets not lose our minds here, I am confused by a code section. :laughing:


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## MTW (Aug 28, 2013)

BBQ said:


> Whoa!!!
> 
> Lets not lose our minds here, I am confused by a code section. :laughing:


Close enough. :laughing:


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## Hack Work (Dec 29, 2013)

This discussion has officially made it's way into Mike Holt's forum territory.


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## Deep Cover (Dec 8, 2012)

BBQ said:


> With a fused disconnect at the unit you have a violation.
> 
> From the 50 amp to the fused disconnect is a feeder and would require 50 amp rated conductors.
> 
> From the fused disconnect to the unit would be a 35 amp branch circuit and could use the 12 AWGs.



I guess that would be correct...brain fart.:001_huh:


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## bullmike (Jun 13, 2011)

Yeah but if you had a Roof Top Unit that a 30 amp disconnect on it . (from the factory) But the blueprints call for a 3 phase 20 amp ckt. The 20 amp breaker in the panel limits the RTU. Some drugstores have this arrangement.


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## MTW (Aug 28, 2013)

bullmike said:


> Yeah but if you had a Roof Top Unit that a 30 amp disconnect on it . (from the factory) But the blueprints call for a 3 phase 20 amp ckt. The 20 amp breaker in the panel limits the RTU. Some drugstores have this arrangement.


But what does the unit's nameplate call for? That's what matter as blueprint specs are notoriously unreliable for HVAC equipment sizing.


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