By how many degrees below the evaporator outside surface temperature should the condenser fan cutout temperature be set?

By how many degrees below the evaporator outside surface temperature should the condenser fan cutout temperature be set?

• A. Five degrees
• B. Fifteen degrees
• C. Ten degrees
• D. Twenty degrees

Answer: (C)

A temperature differential is used to decide when the condenser fan should stop running, so you’re not wasting power while the load is already low. Setting the condenser fan cutout to occur a small amount below the evaporator outside surface temperature gives the system a comfortable margin to cease fan operation once heat rejection requirements drop, while still staying stable and avoiding rapid cycling. Ten degrees is a balanced choice because it provides enough headroom to prevent short cycling if outdoor conditions fluctuate, yet isn’t so large that the fan stays on longer than necessary and wastes energy. If the differential were smaller, the system would cycle more often with minor temperature changes. If it were larger, the fan could stay on longer than needed, increasing energy use and potentially stressing the components. So, ten degrees below the evaporator outside surface temperature is the best compromise to keep operation efficient and reliable.

A temperature differential is used to decide when the condenser fan should stop running, so you’re not wasting power while the load is already low. Setting the condenser fan cutout to occur a small amount below the evaporator outside surface temperature gives the system a comfortable margin to cease fan operation once heat rejection requirements drop, while still staying stable and avoiding rapid cycling.

Ten degrees is a balanced choice because it provides enough headroom to prevent short cycling if outdoor conditions fluctuate, yet isn’t so large that the fan stays on longer than necessary and wastes energy. If the differential were smaller, the system would cycle more often with minor temperature changes. If it were larger, the fan could stay on longer than needed, increasing energy use and potentially stressing the components.

So, ten degrees below the evaporator outside surface temperature is the best compromise to keep operation efficient and reliable.