A/C wire size.

[Jaybone812]

I would set a lower bar, especially for HVAC techs who are allowed to install wiring and may not do any voltage drop calculations. If they said "I'm leaving expansion in case they go to a 5 ton with a 41A MCA and this cable is sufficient for that", it should be fine for a much smaller unit. It also happens when you remove a system that had a larger wire than you need now with a unit that is more efficient and has a lower MCA. No need to rip out a cable when the old system with a 30A cable that was sized fine now has a 15A unit on that same wiring.

And I’d never question or look twice if an existing feed ended up being oversized because for a newer more efficient unit . My thought process would apply to new installs in situations like guys thinking when sizing the ocpd for hvac equipment they have to size it in accordance with 240.4(d)(1-8)- match wire to breaker . That’s the type lack of knowledge and I’m not letting them use the exception
Common sense and real world scenario would always factor in because if you have it on your truck and it’s bought and paid for you’ll use the larger feed to save the money .


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