I am curious if anybody has had these same issues? I have had to replace 2 lower and 1 upper exchanger as well as a steam generator, all of the blowers, burners, electrodes, gas valves, pumps, solenoids and a main PCB. We had really hard water and have since added a water softening system but they both had popping issues even though I was keeping the flue gas dialed in. Any ideas why I have had all of these failures within the first 3 years of operation.? They do get a lot of use but so does our hospital to the north and they don't have as many issues as us.