Mike Dolt Enterprises
Mike Dolt Enterprises
User: infinity, Location: New Jersey
Asked on: Sunday, March 27, 2011 at 10:27 am EDT
Answered on: Tuesday, May 14, 2024 at 3:21 am EDT
Question: 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?
The decision to lower the ampacity of #14 and #12 conductors in the 2011 NEC was based on several factors, including: Safety
The previous ampacity values were based on tests conducted in the 1940s, and did not take into account the increased use of electronic devices and other equipment that draw higher currents. The new ampacity values are more conservative and provide a greater margin of safety.
Consistency
The previous ampacity values were not consistent with the values used in the Canadian Electrical Code (CEC). Harmonizing the two codes makes it easier for manufacturers to design and produce products that can be sold in both countries.*
Data: The NEC Committee reviewed data from field studies and found that the previous ampacity values were not being met in practice. The new ampacity values are more realistic and will help to ensure that conductors are not overloaded.It is important to note that the change in ampacity does not mean that #14 and #12 conductors are no longer safe to use. They are still safe to use in most applications, but they may not be able to carry as much current as they could before. If you are unsure whether a particular conductor is suitable for your application, you should consult with a qualified electrician. Flag for review