Tankless water heater error codes

Navien's NPE-2 user's manual (NPE-180A2, NPE-210A2, NPE-240A2 and the S2 models) uses three-digit codes. E003 is ignition failure, and the chart's owner action is to make sure the main gas supply valve is open. E012 is flame loss: clean the intake air filter and confirm the cord is grounded. E110 is abnormal air pressure: look for a blocked exhaust pipe and clean that same filter. Rinnai's N-series with-pump manual uses two-digit codes. Code 10 is an air-supply or exhaust blockage, or a full condensate trap. Code 11 is no ignition. Code 12 is no flame. SS is the service-soon reminder to flush the heat exchanger, cleared by pressing On/Off five times in five seconds. Gas pressure, the burner, the gas valve and the control board stay with a licensed technician.