Accelerated depreciation is not available for HVAC unless it is nonresidential.
The law known as the Tax Cuts and Jobs Act (TCJA), P.L. 115-97, makes HVAC costs eligible for expensing under Sec. 179. To be eligible, the HVAC costs must be for nonresidential real property that is placed in service after the date the property was first placed in service.
Did you enter it as an asset in 2020 to be depreciated? It should carry over.
