Noritz Water Heaters Error Codes

10

Water heater shuts down and displays error code 10; unit may run briefly then stop, often during high-demand usage.

Exhaust / Air Supply Blockage

11

Water heater will not ignite; display shows error code 11; no hot water at any fixture.

Ignition Failure

12

Burner lights briefly then goes out; display shows error code 12; intermittent hot water that quickly turns cold.

Flame Loss / Flame Rod Detection Failure

14

Unit shuts down with error code 14; may occur after extended operation or at high temperature setpoints.

Thermal Fuse / Overheat Cutoff Activation

16

Water temperature overshoots setpoint; unit shuts down with error code 16, often during low-flow usage such as handwashing.

Outlet Water Overheat

20

Unit displays error code 20 and will not operate; may occur after power issues or internal fault.

Internal Safety Control / High Temperature Limit Fault

29

Error code 29 appears; unit may shut down during operation, especially on condensing Noritz models with condensate drain.

Condensate Drain Blockage / Neutralizer Fault

31

Error code 31 displayed; unit may not start or may shut down shortly after startup.

Inlet Thermistor Fault

32

Error code 32 displayed; unit may operate erratically or shut down.

Outlet Thermistor Fault

33

Error code 33 appears; unit may not modulate correctly or may shut down.

Heat Exchanger Thermistor Fault

34

Error code 34 displayed; unit may shut down or fail to start.

Combustion Air Temperature Sensor Fault

38

Error code 38 appears; unit may not fire or may shut down shortly after ignition.

CO2 / Combustion Feedback Abnormality

41

Error code 41 displayed; unit may not start or may shut down unexpectedly.

Freeze Protection Sensor Fault

42

Error code 42 appears; unit may not fire or may shut down intermittently.

Fan Motor / Combustion Fan Abnormality

43

Error code 43 displayed; unit may not operate.

Internal Circulation Pump / Flow Control Fault (models equipped with pump)

45

Error code 45 appears; unit may not operate in recirculation mode.

External Recirculation Pump / Control Fault

51

Error code 51 displayed; unit may not respond correctly to remote controller commands.

Remote Controller Communication Fault

52

Error code 52 appears; unit may not fire or may shut down.

Modulating Gas Valve Signal Fault

57

Error code 57 displayed; unit may shut down during operation.

Burner Overheat / Abnormal Combustion

61

Error code 61 appears; unit may not start or may shut down.

Combustion Fan Motor Lock / Speed Fault

65

Error code 65 displayed; unit may not operate correctly in recirculation or may shut down.

Flow Control Valve / Bypass Valve Fault

66

Error code 66 appears; unit may not modulate water flow correctly.

Bypass Flow Control Valve Fault

67

Error code 67 displayed; unit may not start.

PCB / Control Board Fault

70

Error code 70 appears; unit may not operate or may behave erratically.

Internal PCB Configuration / Parameter Fault

71

Error code 71 displayed; unit may not operate.

Gas Valve Drive Circuit Fault

72

Error code 72 appears; unit may not detect flame correctly.

Flame Sensing Circuit Abnormality

73

Error code 73 displayed; unit may not operate after service or configuration changes.

Parameter Setting / Dip Switch Conflict

90

Error code 90 appears; unit may shut down during operation.

Abnormal Combustion / Gas Combustion Fault

92

Error code 92 displayed; unit may not operate.

Fan Speed / Combustion Feedback Fault

93

Error code 93 appears; unit may shut down or fail to start.

Combustion Control / Feedback Fault

94

Error code 94 displayed; unit may shut down during operation.

Flame Loss During Operation / Combustion Abnormality

95

Error code 95 appears; unit may not operate.

Abnormal Internal Temperature / Overheat Protection

99

Error code 99 displayed; unit shuts down and will not operate.

Flame Detection Failure / Safety Lockout

Symptom

Hot water temperature fluctuates between hot and cold during a shower; no error code displayed.

Temperature Fluctuation / Short Cycling

Symptom

No hot water anywhere in the home; Noritz water heater display is blank (no power).

No Power to Water Heater

Symptom

No hot water; Noritz unit has power but does not start when hot water taps are opened (no error code displayed).

Flow Sensor Not Detecting Demand

Symptom

Noritz water heater cycles on and off rapidly when a small hot water demand is present (e.g., handwashing).

Short Cycling at Low Flow

Symptom

Noritz water heater exhaust smells strongly of gas or combustion fumes; occupants may notice headaches or irritation.

Combustion / Venting Safety Issue

Symptom

Noritz water heater fan runs but burner does not ignite; no error code displayed, intermittent issue.

Intermittent Ignition / Weak Spark

Symptom

Noritz water heater frequently shuts off when multiple fixtures are used simultaneously; water goes cold until some fixtures are closed.

Capacity Overload / Flow Exceeds Heater Rating

Symptom

Noritz water heater installed outdoors will not operate in cold weather; visible ice or frost on piping or unit.

Freeze Protection Failure / Frozen Piping

Symptom

Noritz water heater is leaking water from the bottom of the unit or from internal components.

Internal Water Leak

Symptom

Noritz water heater makes loud banging or popping noises during operation.

Scale Buildup / Kettling in Heat Exchanger

Symptom

Remote controller for Noritz water heater is unresponsive or displays no information, while the heater itself appears to operate.

Remote Controller Power / Communication Issue

Symptom

Water is warm but not reaching the set temperature; Noritz unit runs continuously without error codes.

Insufficient Heating / Under-Firing

Symptom

Water leaking from the pressure relief valve discharge pipe near the Noritz water heater.

Relief Valve Discharge / Overpressure or Overtemperature