2011-60? C Ampacity Changes For #14 and #12 Conductors

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infinity

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Just took a code update class and they mentioned that the ampacity for several conductors had been changed in the 2011 NEC. The one major change is that now in the 60? C column #14 and #12 conductors are lowered by 5 amps to 15 amps and 20 amps respectively. This can have an impact when using NM cable to feed AC units and motors.

It seems rather odd to me that the substantiation for this change was to move the table more inline with the Canadian Electrical Code where the tables actually originate from. I find this to be rather bogus. Were the values in the old table really a problem from a safety standpoint?
 

Dennis Alwon

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Just took a code update class and they mentioned that the ampacity for several conductors had been changed in the 2011 NEC. The one major change is that now in the 60? C column #14 and #12 conductors are lowered by 5 amps to 15 amps and 20 amps respectively. This can have an impact when using NM cable to feed AC units and motors.

It seems rather odd to me that the substantiation for this change was to move the table more inline with the Canadian Electrical Code where the tables actually originate from. I find this to be rather bogus. Were the values in the old table really a problem from a safety standpoint?

Yeah that was one of the first things I noticed. They also changed the ampacity of other conductors also. #3 is now 115 amps at 90C, #1 at 145 and a few others.
 

G._S._Ohm

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Is selling more copper a foreseeable consequence of the change?
Does Canada have less fires per house per year due to wiring than we do?
How many lives were lost per year before the change, and how many are expected to be lost after the change?
 
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Dennis Alwon

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Is selling more copper a foreseeable consequence of the change?
Does Canada have more fires per house per year due to wiring than we do?
How many lives were lost per year before the change, and how many are expected to be lost after the change?

It has nothing to do with price of copper. Some of the info I stated above has a higher ampacity. #3 at 90C in the 2008 was 110 amps and in 2011 it is 115 amps. Not all changes in the code are based on deaths.
 

infinity

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It just irks me that there is absolutely no safety substantiation to the lowering of the conductor ampacity yet the CMP approved it. I thought that the NEC was a safety code?
 

Dennis Alwon

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Anyone have a printable chart?

Not really but maybe this will help.

ry%3D480
 
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taylorp

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Unless specifically permitted otherwise in Article 240, hasn't the overcurrent protection for #14 and #12 always been 15 and 20 Amps. The ampacities listed in Table 310.16 (2008) for #14 and #12 were really a starting point for derating anyway.

So yes, they lowered the ampacity for derating purposes. Unless you derate, you still protect them according to the same rules as before.
 

infinity

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Unless specifically permitted otherwise in Article 240, hasn't the overcurrent protection for #14 and #12 always been 15 and 20 Amps. The ampacities listed in Table 310.16 (2008) for #14 and #12 were really a starting point for derating anyway.

So yes, they lowered the ampacity for derating purposes. Unless you derate, you still protect them according to the same rules as before.


Not really. If you had a load that wasn't bound by 240.4(D), such as an AC unit or a motor, you could use the old 60? C ampacity of (i.e.-#12 NM cable @ 25 amps) to feed that unit. Now you're stuck with an ampacity for that same exact conductor that is 5 amps less or 20 amps. I have no problem with that if the substantiation was that the #12 @ 25 amps were a safety hazard.
 
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taylorp

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The true ampacity of #14 and #12 has always been 15 and 20 Amps. Otherwise the NEC would have allowed you to protect them with a 20 Amp and 25 Amp overcurrent device under "normal" conditions of use all along. The new ampacity values are based on mathematical calculations and IEEE standards.

Apparently the CMP agreed with proposal because they passed it. Now I agree that from a safety standpoint, it doesn?t make any sense. But for me, it is not a big deal. The application of using a #14 or #12 at the higher Amperages did not seem to be a common practice anyway. Many people don?t even bother using a #12 @ 25 amps for the handful of application scenarios in which it might apply.

Even the gentlemen who voted ?no? on the proposal argued that quote: ? . . . additionally, 240.4(D) limits the ampacity of AWG 14 and 12 copper by limiting the maximum overcurrent protection for these conductors.? So the common practice was to use them at the 15 and 20 Ampacities anyway even when allowed to do otherwise.
 
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taylorp

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According to the Report on Proposals, the change in Ampacity values was submitted by James Daly, the U.S. Co-Chair of the NEC/CEC Ampacity Harmonization Task Group. It seems that since the NEC has gone global, other countries are getting involved in contributing input to the code. Apparently the Canadians were pointing out that our values were out of range on certain wire sizes. The committee stated that they had "technically substantiated values" which it seems are based on mathematical calculations.

I agree that there does not seem to be a safety problem. However, in the interest of ?harmonization? with our Canadian brothers, we agreed to change our Code Table Ampacity values in 310.16 (2008), now Table 310.15(B)(16) in the 2011 Code. Maybe the Canadians are correct in their proposal?

Of the 11 members of Code-Making Panel No. 6, Ten members voted to Affirm. One voted Negative. These are the groups represented who voted Yes:

National Electrical Contractors Association (2 members)
American Chemistry Council
International Association of Electrical Inspectors
Independent Electrical Contractors
International Brotherhood of Electrical Workers
Institute of Electrical & Electronics Engineers
The Aluminum Association
Underwriters Laboratories
Copper Development Association

The group representative who voted No was:

Electric Light & Power Group/EEI

Electricians, Inspectors, Contractors, Engineers, UL, and Industry representatives all voted yes. The Power Company voted no. Who would have thought???????
 

raider1

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The true ampacity of #14 and #12 has always been 15 and 20 Amps. Otherwise the NEC would have allowed you to protect them with a 20 Amp and 25 Amp overcurrent device under "normal" conditions of use all along. The new ampacity values are based on mathematical calculations and IEEE standards.

Do you have something to back that up?

Apparently the CMP agreed with proposal because they passed it. Now I agree that from a safety standpoint, it doesn?t make any sense. But for me, it is not a big deal. The application of using a #14 or #12 at the higher Amperages did not seem to be a common practice anyway. Many people don?t even bother using a #12 @ 25 amps for the handful of application scenarios in which it might apply.

And you feel that is justification to reduce the ampacity of #14 and #12 at the 60 degree column?

Even the gentlemen who voted ?no? on the proposal argued that quote: ? . . . additionally, 240.4(D) limits the ampacity of AWG 14 and 12 copper by limiting the maximum overcurrent protection for these conductors.? So the common practice was to use them at the 15 and 20 Ampacities anyway even when allowed to do otherwise.

240.4(D) absolutely DOES NOT limit the ampacity of any conductor. 240.4(D) limits the overcurrent protective device under certain circumstances but has no bearing on the actual ampacity of the conductor.

Chris
 

xformer

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240.4(D) absolutely DOES NOT limit the ampacity of any conductor. 240.4(D) limits the overcurrent protective device under certain circumstances but has no bearing on the actual ampacity of the conductor.

Agreed.
 
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rbalex

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One can't help but wonder what is the occupation of the person who submitted the proposal. :confused:
Jim Daly works for General Cable. He is the NEMA Principal rep on the TCC and an Alternate on CMP6. However, I'm sure his role in the NEC/CEC Ampacity Harmonization Task Group was the primary basis for the submittal. Often the Secretary (or Co-Chair in this case) of a Task Group has the responsibility to submit Proposals on behalf of the Task Group.
 
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