We are currently looking at an application where there has been a complaint that the pump is too noisy. The pump has been replaced once and the system is only two years old.
The system is a boiler loop feeding a plate heat exchanger, the pump is an inline circulator and temperature is controled with a three-way valve. My concerns with the system is that: there is no air seperator/air release, there is no check valve after the pump, there is no expansion tank, and finally the system was never balanced properly.
The problems I envision are: air in system causing cavitiation-like damage, flow from other pumps spinning impeller in reverse while not operating and causing start-up problems, pump running through the pump curve as head is lower than expected and velocity through pump and heat exchanger is too high.
I am going out to check the installation. Is there anything else I should be looking for, and do my assumptions about the possible (probable) causes of the problem look reasonable?