A/C Feeder size Question 14 ga on 20 amp?

When inspecting service panels, I compare the wire sizes to the breaker sizes. #14 AWG (Cu) - Max 15 amp breaker, #12 AWG (Cu) - Max 20 amp, and so on. Many times I will catch a #14 AWG (Cu) attached to a 20 amp breaker and call that out as a potential safey hazard.

Here’s the question, What is correct call when there is a #14 AWG (Cu)attached to a 20 AMP 220V breaker for an A/C unit? The namplate of the A/C is attached.

Minimum Circuit amps 12.6 (#14 AWG Cu is OK)
Running Load Amps 9.0 x 125% = 11.25 (#14 AWG CU is OK)
Maximum breaker size 20 amps OK

14 AWG Cu on a 20 amp breaker. Circuit breaker too large for wire capacity. Recommend evaluation by a licensed electrician

I evidently ticked off the electrician when he was called back to this property because of this. Without being technically exhaustive (knowing what circuits feed what in the home) How should this be reported?

I will be talking with the local AHG on Monday morning. I’ve also have seen #12 AWG on a 25 amp and 30 amp breakers in the past.



The #14 on the 20 amp breaker was fine. It goes by manufacturer’s recommendations. When you have any type of a/c, follow the nameplate info on the back. As you stated, the min ckt amps is 12.6. The #14 will be the minimum you can use. It is also stated that 20 amp is the max OCPD you can use.
If you want to follow along in the code book 2005 NEC). 204.4(G) says to follow table 204.4(G). The table in turn says to follow the rules in 440 art III. 440.22 © says to follow manufacturer’s values.


Don’t know why the electrician was p.o’d. He got some money on a call for doing nothing. :slight_smile:


It’s perfectly acceptable and common practice. The breaker size will almost always exceed the conductor-ampacity in the circuit for the condenser unit.

So to correctly evaluate a service panel with an A/C system, the manufacture’s data takes precidence. HMMM… So one has to be a little more careful while doing this inspection and actually be a little more technically exhaustive.

What I’m getting at is it’s better to call out for an electrician to evaluate the system if the components are not identified on the panel in the first place rather than assuming the conductors actually go to the a/c if they happen to be undersized.

What happens for well pumps when the manufacture’s data plate is rarely available? According to the NEC, these conductors could also be undersized for the breaker attached.

Use Article 440 in the NEC for guidance; this is where the information for the calculation for these types of units is covered.

The product label is necessary and provides the information related to Section 110.2.

Question: Has 440.14 been complied with?

Go to www.bussmann.com and find even more information. :wink: