ComboverFish writes:

So how do you all feel about the accuracy of DELTA for the purposes of
condemning an A/C system? Do I really have a problem? Or may the
inspector have seen that the unit was around 15 - 20 years old with
fin damage and just found an easy way to condemn it that isn't
accurate? (much less than 5% fin damage)

That old, and performing poorly? It is simply worth next to nothing. Deal
accordingly.

Cf Proverbs 20:14