The minimum total area of outside and return air ducts or openings to a heat pump shall be not less than ______ square inches per 1000 Btu/h output rating.

The minimum total area of outside and return air ducts or openings to a heat pump shall be not less than ______ square inches per 1000 Btu/h output rating.

• A. 6
• B. 2
• C. 8
• D. 7

Answer: (A)

Airflow openings for a heat pump must be sized so that their combined area meets a minimum per unit of capacity, ensuring enough air can move through the system for proper cooling, heat rejection, and pressure balance. The required minimum is 6 square inches of outside plus return air openings for every 1,000 Btu/h of the heat pump’s output. This proportional rule keeps the coil from overheating and helps the system operate efficiently. For example, a 24,000 Btu/h unit would need at least 24 × 6 = 144 square inches of opening area. Values smaller than this don’t meet the code’s minimum, while larger values exceed the minimum but aren’t required by the standard.

Airflow openings for a heat pump must be sized so that their combined area meets a minimum per unit of capacity, ensuring enough air can move through the system for proper cooling, heat rejection, and pressure balance. The required minimum is 6 square inches of outside plus return air openings for every 1,000 Btu/h of the heat pump’s output. This proportional rule keeps the coil from overheating and helps the system operate efficiently. For example, a 24,000 Btu/h unit would need at least 24 × 6 = 144 square inches of opening area. Values smaller than this don’t meet the code’s minimum, while larger values exceed the minimum but aren’t required by the standard.