Tankless Water Heater Error Codes in Fairfield: What Rheem, Navien, Rinnai, and Noritz Codes Mean

A code on your tankless water heater’s display is the unit telling you what it found wrong. That narrows the problem from “no hot water” to a specific fault, and tells you whether a reset is worth trying or a technician is needed. The catch is that the same number can mean different things on different brands, so the code only helps if you read it against the right brand.

This guide covers the four brands most often found in Fairfield homes — Rheem, Navien, Rinnai, and Noritz — using code meanings from Fast Water Heater’s all-brands error code guide and manufacturer documentation. Every meaning below comes from that named source; codes that could not be verified are left out. Before anything else, try a power cycle: turn the unit off at the breaker or unplug it, wait 30 seconds, and restore power. Never open a gas or electrical connection, and never keep resetting a code that comes straight back.

If a code keeps returning, we can take a look. We are open 09:00-17:00 daily. Call +1 707 574 9715 to book a visit.

How to Read a Code

Start with the brand, then the code, then your manual. Rheem’s older units show plain numbers; current IKONIC models add an “A” (11 shows as A011). Navien codes carry an “E” prefix (E003). Rinnai and Noritz use plain numbers, Rinnai also using letter codes such as LC. Codes vary between generations, so check your manual.

Every code below ends with one of three verdicts: “Try reset first” (reset once; call a pro only if it returns), “Schedule service” (maintenance is due, not a failure), or “Call a pro” (not a homeowner fix).

Rheem Error Codes

11 (A011 on IKONIC models) — No ignition. Try reset first. The unit tried to light but found no flame. Check the gas valve is open and other gas appliances work, then reset once; if it returns, call a pro.

12 (A012 on IKONIC models) — Flame failure. Try reset first. The burner lit but lost its flame — A012 appears after repeated losses. Low gas pressure, air in a new gas line, and a dirty flame rod are common causes. Reset once; if it returns, call a pro.

14 (A014 on IKONIC models) — Overheat limiter tripped. Call a pro. The over-heat safety limiter has tripped. Do not keep resetting it.

1L (A01L on IKONIC models) — Scale buildup, flush needed. Schedule service. Mineral scale is building up in the heat exchanger — the code Fairfield’s hard water produces most often. Schedule a descaling flush; our guide to tankless water heater descaling in Fairfield explains what it involves.

Navien Error Codes

Navien’s manual says not to repair or replace parts unless the manual tells you to. For most Navien codes, a technician is the safest call.

E003 — Ignition failure. Try reset first. The unit could not light the burner. Navien’s manual says to check the main gas supply valve is open, and a seismic gas shutoff valve, if you have one, has not tripped. Reset once; if it returns, call a pro.

E012 — Flame loss. Try reset first. The burner lit but lost its flame. Navien’s manual says to clean the air intake filter and check the unit is grounded; if it returns, call a pro.

E016 — Heat exchanger overheating. Call a pro. The heat exchanger is running too hot, often from scale or restricted flow. Navien’s manual calls for cleaning the inlet filter and flushing the exchanger, so call a pro for descaling.

E030 — Exhaust temperature too high. Call a pro. The exhaust temperature is too high. Turn the unit off and call a pro.

E110 — Abnormal air pressure or exhaust blockage. Call a pro. Combustion air or exhaust is not moving as it should. Navien’s manual says to check the exhaust pipe for obstructions and clean the air intake filter. Leave the unit off and call a pro.

E760 — Flush or service reminder. Schedule service. Not a fault: the set service interval has run out and a flush is due. Schedule a descaling flush.

Rinnai Error Codes

To reset a Rinnai, press On/Off, wait 5 seconds, and turn it back on. Codes vary between condensing and non-condensing models, so check your manual.

10 — Air supply or exhaust blockage. Try reset first. The air intake or exhaust is blocked; on condensing N-Series units, the condensate trap may also be full. Check the outside vent terminals; if clear, call a pro — vent problems can create a carbon monoxide risk.

11 — No ignition. Try reset first. The unit tried to light but found no flame. Common causes are a closed gas valve, low gas pressure, or a blocked air intake. Check the gas valve is open, then reset once; if it returns, call a pro.

12 — Flame failure. Try reset first. The burner lit but lost its flame. Reset once; if it recurs, call a pro.

14 — Thermal fuse tripped, overheating. Call a pro. The unit overheated and the thermal fuse tripped.

LC (LC0 to LC9) — Scale buildup in the heat exchanger. Schedule service. Mineral scale is building up in the heat exchanger. LC is the one Rinnai code that lets the unit keep running, so it is easy to ignore — but repeated LC codes lock it out until the exchanger is flushed and the code is reset. Schedule a flush; read our tankless descaling guide for Fairfield.

SS — Service soon. Schedule service. On SENSEI and N-Series models, a timed flush reminder — not a fault. Press On/Off five times within five seconds to clear it, then schedule service.

Noritz Error Codes

To reset a Noritz, turn the unit off and back on. Codes vary by series (NRC, NRCP, NRCR), so check your manual.

11 — Ignition failure. Try reset first. The unit did not detect a flame. Common causes are a gas supply problem, an airflow problem, or debris on the igniter. Check the gas valve is open and reset once; if it returns, call a pro.

12 — Flame loss. Try reset first. The burner lit but lost its flame; low gas pressure when several gas appliances run at once is a common cause. Reset once; if it recurs, call a pro.

16 — High outlet temperature. Try reset first. The outgoing water got too hot, often from scale buildup. Clean the cold water inlet filter if you can reach it; if it persists, call a pro.

31, 32, and 33 — Temperature sensor failure. Call a pro. A temperature sensor has failed — 31 cold water inlet, 32 hot water outlet, 33 heat exchanger outlet. Call a pro to replace the sensor.

90 — Combustion abnormality. Call a pro. The unit failed to reach the set temperature after three attempts, usually from low gas pressure or a blocked air intake or exhaust. The air path needs inspection and cleaning.

C1# — Descaling reminder, condensing models. Schedule service. The heat exchanger is due for a descaling flush. Schedule a flush.

Which Codes Mean Scale in Fairfield

Fairfield’s hard water makes the scale codes the most common ones you will see: Rheem 1L, Navien E016 and E760, Rinnai LC and SS, and Noritz 16 and C1#. If your unit shows one of these, the useful response is a descaling flush, not a reset loop: a reset clears the display but not the scale, and the code will come back. Our tankless descaling guide explains the timing, and regular water heater maintenance keeps the flush on a rhythm.

When a Code Means Stop, Not Reset

Some codes are safety codes: leave the unit off. Any code tied to venting or exhaust — Navien E110 and E030, Rinnai 10 — can involve carbon monoxide; leave the unit off until a technician checks the vent path. Any overheat code that returns after one reset — Rheem 14, Rinnai 14, or a persistent Noritz 16 — should not be reset again; repeated resetting can mask a fault that is getting worse.

If you smell gas, do not touch the unit or switch lights on or off near it. Leave the house and call your gas provider from outside.

The Bottom Line

Write the code down, note the brand and model, and try one power cycle. If the code clears and stays cleared, you are done. If it returns, or if it is a scale code, a venting code, or an overheat code, the next step belongs to a technician. Our water heater repair service covers that diagnosis, and if replacement makes more sense than repair, our tankless water heater installation service covers sizing and options; see our tankless versus tank water heater comparison for Fairfield for how tankless compares with a tank unit. We are open 09:00-17:00 daily. Call +1 707 574 9715 to book a visit.