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Navien CH-240 knocking/banging noise
As if I didn't have enough trouble with my system, today I was powering up after a power outage and the boiler starts making a banging noise the likes of which I've never heard. I am neither an HVAC pro nor a plumber, but I know machinery and this was NOT a normal noise. I literally thought an animal had crawled in there and was trying to get out. It was a loud knocking/banging which was shaking the whole unit. The strangest part was that it persisted after I powered it down. It seemed to be coming from the top of the heat exchanger (upper right) near what looked to be some sort of solenoid. Not sure if this was stuck or if it was trying to push the mother of all air bubbles through but long story it was not working, first firing off error 16 (overheating heat exchanger), 01 (water boiling in HE), and 46 (abnormal thermistor). I tried cleaning all filters (both the water filters were clean) as well as the air filter (which was not as clean). Eventually after several on/off cycles it began working normally again.
I will say for sure that I have had the DHW inlet turned off for a few days (the house is still under some renovation)
Typically the unit will do the "singing pipes" routine which from what I understand is just from expansion. This was definitely not that. It also did not sound like trapped air (I hope!) but I guess it's possible. It went through an air purge cycle after I pulled out the supply filter. As I mentioned it works now, just wanted to see if anyone has seen this and whether there will be anything to watch out for in the future.
Thanks for any info!