Final answer:
After evacuating the system, 12 oz of refrigerant should be added to the initial factory charge of 80 oz, resulting in a total of 92 oz of refrigerant for the 35 ft line set.
Step-by-step explanation:
The student asked how much refrigerant should be added to the system after it has been evacuated due to a compressor replacement in an existing split system with a 35 ft line set. Since the factory charge of the condensing unit is for a 15 ft line, we must adjust for the additional 20 ft of line (35 ft - 15 ft). Using the given rate of 0.6 oz per foot, we calculate the additional amount of refrigerant needed.
Additional refrigerant required = 0.6 oz/ft × 20 ft = 12 oz
Therefore, after evacuating the system, 12 oz of refrigerant should be added to the factory charge of 80 oz, resulting in a total charge of 92 oz.