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Rinnai RUCS75 randomly stops heating water
My Rinnai (about 1 year old) will stop hearing water randomly even thought he faucet is on full hot and it originally turn the heater on and kept it hot for 2-4 minutes... turning water all the way off and back on will restart the heater and then 2-4 minutes turn cold again.
I am puzzled as this seems like a flow issue, but no errors are shown on the display window.
Secondly the heater will make a loud vibration/groan noise occasionally and I am not sure what would cause this... the problem are mutually exclusive.
Any guidance would be great