Good Afternoon all,
I have a 4-5 year old sta rite sr400lp heater. It has become recently problematic. When turned on, starts up normally, heats for a while, then a very loud metallic clanging noise occurs for about 4-5 minutes, the heater shuts down, waits for a while, then restarts. The clanging noise seems to be more frequent at higher temperatures. Eventually, it reaches the goal temperature but takes much longer than usual because of all the shut downs, not to mention the annoying clanging. If it helps, the clanging is never heard below 90 degrees or when the pool runs with the heater off, and is clearly metallic in nature. It is irregularly irregular -- think of a marble bouncing around and intermittently hitting a fan blade, rather than a rhythmic tapping / hitting. I have had a repairman come out and tell me that there is a "water impeller" in the sealed bottom unit for pumping water that is damaged, and the only solution is to change the entire heater. Being of a curious (and cynical) nature, I looked at the full schematics of the unit and fail to find such a "water impeller" anywhere in the diagram. While I am unfamiliar with pool equipment, I routinely repair all kinds of devices. It seems to me, whether right or wrong, that all water movement in the system comes from the main pump which pushes the water through the filter and the heater, with no separate pump unit in the heater. The fact that he quoted me a price more than double than the highest price I can find for the heater made me even more suspicious. I know I have the ability, knowledge and tools to safely and correctly swap out the heater itself, but I don't even know if it is necessary. I have found one such similar listing on another website, where the noise was not metallic in nature, but caused by steam clanging from a broken manifold bypass valve bypassing the boiler. Has anyone run across something like this or have any other ideas as to what might be causing the problem? I would love to swap out a module rather than coughing up the big bucks for a brand new heater. Any and all comments or suggestions, including diagnostic advice would be greatly appreciated. Thank you.