Noritz tankless water heater code 10
Your series decides which reading applies. Across the 4 Noritz series documented here, code 10 is listed as combustion fault, btu drop (3 series) and combustion fault recorded in history (1 series). Find your series in the table below, where those readings route to a professional.
What code 10 means on each Noritz series
| Series | What it means | Verdict | Typical cost |
|---|---|---|---|
| EZ Series & NCC199CDV | Combustion fault recorded in history | Call a pro | $0–$900 |
| NCC199 & NRC111 | Combustion fault, BTU drop | Call a pro | $0–$900 |
| NR50, NR66 & NR71 | Combustion fault, BTU drop | Call a pro | $0–$900 |
| NR98 & NR111 | Combustion fault, BTU drop | Call a pro | $0–$900 |
Each row opens the full page for that generation. We hold manuals for EZ Series & NCC199CDV, NCC199 & NRC111, NR50, NR66 & NR71 and NR98 & NR111, and each one gets its own reading of code 10 — what Noritz documents, what you can safely check yourself, and what the repair should cost.
What each manual actually says
The table above compares 4 series in four columns, which is enough to route you and not enough to explain anything. This is the Noritz wording behind each row, one entry per manual, so you can see where the 4 readings of code 10 agree and where they part company.
EZ Series & NCC199CDV — Combustion fault recorded in history
A combustion abnormality the unit did not stop for. Noritz notes this one as "only memorized in error code history", which means you will normally find it by reading the history rather than by seeing it on the controller. The checklist is the full combustion set — air supply vent and exhaust vent for blockage, gas supply pressure checked by a professional, the condensate drain line clogged or frozen, the drain pipe sloping down, and the dip switch settings on the circuit board.
NCC199 & NRC111 — Combustion fault, BTU drop
Noritz labels this combustion abnormality with a BTU drop, and adds the part that matters: the unit continues working. The heater has noticed its own output falling short and has kept running rather than stopping. The checks are abnormal combustion and the flue for blockage or obstruction, and the power has to be cycled to clear the code.
NR50, NR66 & NR71 — Combustion fault, BTU drop
Combustion abnormality with a BTU drop, and Noritz notes the unit continues working. The checks are abnormal combustion and the flue for blockage or obstruction. On a unit with no remote controller this shows as continuous flashing, and Noritz records that no reset is needed — the heater is available to burn even before you reset it.
NR98 & NR111 — Combustion fault, BTU drop
Noritz labels this combustion abnormality with a BTU drop and notes that the unit continues working. The heater has seen its own output fall short and kept running rather than stopping. The checks are abnormal combustion and the flue for blockage or obstruction, and the power has to be cycled to clear it. Noritz gives this range 90 and 99 for combustion faults that stop the unit and 10 for the one that does not, with no intermediate grades. The NRC661 and NRC711 table spreads the same ground across 901, 902, 903 and 908 — more numbers, and more to go on when something is intermittent.
Does it matter which Noritz you have?
EZ Series & NCC199CDV, NCC199 & NRC111, NR50, NR66 & NR71 and NR98 & NR111 all route code 10 the same way: a professional, at $0–$900. That makes it one of the Noritz numbers you can act on before working out which unit you own.
What to check first, whatever your series
These checks are on the manufacturer's list for every Noritz series that reports code 10, so they are safe to work through before you have identified your exact unit. They also cost nothing.
- Check the vent terminal and air inlet outside for snow, leaves, a nest or anything built against them.
That is 1 of the 3 checks documented for code 10. The rest differ by generation, so if none of those explains it, go to your own series above.
Which Noritz do you have?
On the 4 series that report code 10, the model number on the rating label starts EZ, NCC, GQ, N and NRC — match yours against the 36 listed below. You can also use the full model-number decoder.
Where this comes from
Source: Noritz Service Manual — NRC663 FSV, EZ98DV, EZ111DV, NCC199CDV (Rev. Oct 2017) (p. 32), read Sep 2026 — the manufacturer's own documentation for this Noritz range.
Source: Noritz Service Manual — NR50 / NR66 / NR71 / NR98 / NCC199 / NRC111 / NR111 / NC380 (Rev. July 2011) (p. 55), read Sep 2026 — the manufacturer's own documentation for this Noritz range.
Source: Noritz Service Manual — NR50 / NR66 / NR71 / NR98 / NCC199 / NRC111 / NR111 / NC380 (Rev. July 2011) (p. 54), read Sep 2026 — the manufacturer's own documentation for this Noritz range.
Source: Noritz Service Manual — NR50 / NR66 / NR71 / NR98 / NCC199 / NRC111 / NR111 / NC380 (Rev. July 2011) (p. 56), read Sep 2026 — the manufacturer's own documentation for this Noritz range.
The same number on other brands
Code 10 is not a standard across the industry — every manufacturer publishes its own table. If your unit is not a Noritz, this number means something else entirely:
Parts, guides and symptoms behind code 10
Code 10 on these 4 Noritz series points at 5 parts and 3 symptoms, each named by the manufacturer's own procedure for this code.