To select and size a single-stage pump for an HVAC/R & Solar application, you need to consider factors such as the required flow rate, total head, and system pressure. You should also consider the type of fluid being pumped, its viscosity and temperature, and the pump’s efficiency and power consumption. Proper selection and sizing of the pump are critical to ensure reliable and efficient operation, and to prevent issues such as cavitation, vibration, and overheating. It is recommended to consult with a pump expert or refer to the manufacturer’s documentation for guidance on selecting and sizing the pump.