An upright furnace has been installed in the basement of a residence. The supply air duct to the furnace has an air conditioning coil that uses R22 as its refrigerant. This coil is classified as what type of refrigeration system?

An upright furnace has been installed in the basement of a residence. The supply air duct to the furnace has an air conditioning coil that uses R22 as its refrigerant. This coil is classified as what type of refrigeration system?