Permit required - upsizing part of cable run

[NoahsArc]

I have an old panel in a house going to market, where all the breakers were 20a except the ac which was 40a, and all the wires are 14ga.
I'm swapping out to 15a breakers (all receptacles are 15a, old 50s house).
The 40a is dropping to 20a per ac nameplate max oc. Max amps is 13.8.
Only part of the ac run is 14ga, as its 12ga at the disconnect.
I need to replace that bit of mc to bring it up to 12ga.

I am guessing this technically requires a permit usually, even though nothing is being added only replaced/improved.

 

[CoolWill]

You wouldn't want the city to miss out on their tax would you? I only get permits when I absolutely have to, like when working downtown outside or when the utility requires an inspection. But your average run-of-the-mill interior type residential service, I don't bother with permits. This is just my opinion of course. Some people live and die by them and inspectors would be out of a job if no one got permits.

 

[curt swartz]

Why do you need to upgrade the #14 to #12?

You state that the MOCP is 20 amps and maximum amps is 13.8. I'm guessing the 13.8 is actually the MCA which means the conductors need to be rated for a minimum of 13.8 amps. The overcurrent protection can be 15 or 20 amps.

 

[NoahsArc]

Why do you need to upgrade the #14 to #12?

You state that the MOCP is 20 amps and maximum amps is 13.8. I'm guessing the 13.8 is actually the MCA which means the conductors need to be rated for a minimum of 13.8 amps. The overcurrent protection can be 15 or 20 amps.

Continuous duty?
Startup inrush concern?
Personally, if the equipment says directly anything about OCPD, I just want to install that OCPD size. I don't want to have to worry about nuisance trips. 14ga feels light for an AC, I wouldn't even want a window unit on 14ga, though tbf I have run them off that in my own residence without issue.

Regardless, permit required if I do the thing?

 

[don_resqcapt19]

Continuous duty?
Startup inrush concern?
Personally, if the equipment says directly anything about OCPD, I just want to install that OCPD size. I don't want to have to worry about nuisance trips. 14ga feels light for an AC, I wouldn't even want a window unit on 14ga, though tbf I have run them off that in my own residence without issue.

Regardless, permit required if I do the thing?

With AC units, the nameplate minimum circuit ampacity already includes 125% of the largest motor in the equipment. The start up inrush is taken care of by specifying a 20 amp OCPD for a load of about 11 amps.

 

[NoahsArc]

With AC units, the nameplate minimum circuit ampacity already includes 125% of the largest motor in the equipment. The start up inrush is taken care of by specifying a 20 amp OCPD for a load of about 11 amps.

So you would be fine with 15A CB and 14ga here as curt said, or does it require 20A with 12ga (or 14ga I guess)?

 

[LarryFine]

So you would be fine with 15A CB and 14ga here as curt said, or does it require 20A with 12ga (or 14ga I guess)?

The wiring must be sized at least for the MCA.

The breaker must be no larger than the MOC.

There is nothing else to calculate or figure out.

You often end up with, say, #14 on 20a, #12 on 30a, etc.

 

[don_resqcapt19]

So you would be fine with 15A CB and 14ga here as curt said, or does it require 20A with 12ga (or 14ga I guess)?

I would be fine with 14 AWG on a 20A breaker

 

[LarryFine]

I would be fine with 14 AWG on a 20A breaker

Actually, I would be Fine with any size of wire.