The circulation pump is noisy. (Groaning sound, swishing sound).

Check the pump for air. Loosen the center cap 1/4 turn to vent any air in the pump. Use the air vent bleed cap on the side unit to vent any air at the top of the evaporator waterside inlet. If the unit is equipped with a storage tank vent the expansion tank at the air vent mounted on the tank. Check the water pressure in the system. Minimum operating pressure is 1.5 bar or 21 psig. Vent the remainder of the high points in the system for air.