It was a separate Asset - as it was not the original HVAC system purchased with the house, but replaced the system 10 years ago in 2010 and then this system had to be replaced in 2021 - since tax law required it to be depreciated over the life of the rental property - it had an undepreciated value remaning at the time of replacement and based upon my understanding this is a loss that should have come through on Form 4797 after entering the 'Sale' (replacement) information on the Asset Worksheet.
