HVAC - MCA/MOCPD - 334.80 Redtag

[James@AmericanGrit]

Sorry for the late response here as i went on a much needed vacation and then had to play some catch up.

We are using a fuseless disconnect at the unit.

 

[texie]

I am in OKC, Oklahoma, and I am having an issue here with my AHJ regarding MCA and MOCPD in regards to AC units.

Mike has several videos throughout the years pertaining to this issue and I have learned a lot from them.

When there is a nameplate, the job is pretty easy...IMO

In This situation, I have a 8-2 NMB installed on a 50A breaker at the panel.
Nameplate rating MCA 22.3 MOCPD 50A. I got this information late and played what i thought was a safe call.

I have referred my AHJ to article 240.4(G), which refers to 440, parts lll and Vl.

They have no desire to hear our point of view. They simply refer to 334.80, my understanding is that 440 relieves us from the ampacity constraint here on the conductors.

Has anyone won this debate in writing, anyone have a clearer code path than I?

I am being told that it explicitly that I have no chance here by the chief electrical inspector. I have made they changes they asked for due to not wanting to hold up the project. This isn't me trying to cheap out, its me trying to now prove the chief wrong. Thanks in advance

As others have indicated, the inspector is absolutely wrong. This call of his indicates to me that he does not have an understanding of the basic concepts of how these types of circuits are to be sized and the difference of short circuit VS overload protection. In fact, you could use #10 NM or even #12 if MC (or pipe and wire) and be compliant.
If the inspector sees this as a violation it makes me wonder how he would view an installation with motor circuits. Is he going to walk into a plant with lots of large motors and announce that all the branch circuit conductors have to match the ampacity of the OCPD? Laughable.

 

[mtnelect]

This might help, but since this is based on 1999 NEC the section(s) displayed might have changed to current code. But, this still is an niformative display of the requirements for wiring an HVAC unit.