Tap conductor on 12AWG branch circuit

[480sparky]

Interestingly enough, in 1953, there was no RHH wire listed, just RH (listed as a 60 or 75?C conductor).

In 1956, RHH is listed for the first time as a 90? conductor, the same year the 14/12/10 footnote appears.

So whatever the difference was between RH and RHH back then triggered the lowering of the ampacity, but I can't find anything in either Article 300 or any of the notes to the table to explain it.

 

[LarryFine]

Can you tell the class "WHY" wires were "Coated" when using rubber insulation?:grin:

Soi they could be stripped? I see the molten rubber during manufacture adhering to the conductor.

 

[iwire]

Yes, that would be the 'other aspects of the circuit providing protection'

Not necessarily other overcurrent devices, but other features of the circuit which along with the OCPD permit a rating above 15 (for 14 AWG) to be trusted.

-Jon

I am not following you. :-?

 

[iwire]

Bob, why you tryin' to call me out?

Yes meet me at the swing set after school. :wink:

No, I am just trying to point out that the NEC does allow 14 AWG to be used and protected at 20 amps for other applications.

I don't know why the section is there, but it only applies to some types of circuits so overloading the conductor does not seem to be issue in my mind.

 

[winnie]

Not necessarily other overcurrent devices, but other features of the circuit which along with the OCPD permit a rating above 15 (for 14 AWG) to be trusted.

I am not following you. :-?

All that I am saying is that with loads in general a 20A OCPD is not considered to protect a 14 AWG wire, but with some specific loads a 20A OCPD (or greater) is considered acceptable. This must mean that some aspect of these loads provides protection that a 20A OCPD alone cannot.

The biggie is of course motor circuits (along with appliances and refrigeration/AC loads which are dominated by motors). In these the OCPD may be greater than the ampacity of the conductors...but the required overload protection for the motors is also providing the necessary conductor overload protection.

Perhaps this is simply that motor overload devices are trusted to be more accurate than 20A OCPD devices.

-Jon