Noritz tankless water heater code 90
Your series decides which reading applies. Across the 5 Noritz series documented here, code 90 is listed as combustion fault (3 series), combustion fault, unit shuts off (1 series) and air flow or combustion fault (1 series). Find your series in the table below, where those readings route to a professional.
What code 90 means on each Noritz series
| Series | What it means | Verdict | Typical cost |
|---|---|---|---|
| EZ Series & NCC199CDV | Combustion fault, unit shuts off | Call a pro | $0–$1,000 |
| NCC199 & NRC111 | Combustion fault | Call a pro | $0–$1,000 |
| NR50, NR66 & NR71 | Combustion fault | Call a pro | $0–$1,000 |
| NR98 & NR111 | Combustion fault | Call a pro | $0–$1,000 |
| NRC Series | Air flow or combustion fault | Call a pro | $0–$1,000 |
Each row opens the full page for that generation. We hold manuals for EZ Series & NCC199CDV, NCC199 & NRC111, NR50, NR66 & NR71, NR98 & NR111 and NRC Series, and each one gets its own reading of code 90 — what Noritz documents, what you can safely check yourself, and what the repair should cost.
What each manual actually says
The table above compares 5 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 5 readings of code 90 agree and where they part company.
EZ Series & NCC199CDV — Combustion fault, unit shuts off
The same checklist as code 10, but the unit has stopped rather than just recorded it: 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. Noritz adds that if the display continues after a power cycle, contact the nearest Noritz agent.
NCC199 & NRC111 — Combustion fault
Combustion abnormality, in two grades. Noritz prints the warning indication and the shutdown under the same number: the warning checks abnormal combustion and the flue for blockage, and the shutdown adds checking that the flame ignites all the way across the burner and requires a power cycle to clear.
NR50, NR66 & NR71 — Combustion fault
Combustion abnormality, in two grades under one number. The warning indication checks abnormal combustion and the flue for blockage; the shutdown adds checking that the flame ignites all the way across the burner and needs a power cycle to clear. Continuous flashing on a unit with no remote controller.
NR98 & NR111 — Combustion fault
Combustion abnormality, in two grades under one number. The warning indication checks abnormal combustion and the flue for blockage; the shutdown adds checking that the flame ignites all the way across the burner and requires a power cycle to clear. Noritz splits combustion faults on this table into 90 and 99 and gives them the same checks, where the NRC661 range spreads the same ground across 90, 901, 902, 903 and 908. Fewer numbers here means less to go on, not fewer causes.
NRC Series — Air flow or combustion fault
The unit has shut off over air flow or combustion. Noritz's base check is the flue and air inlet for blockage or obstruction, and the display window separates the severity: 901 is a warning that escalates to a shutdown, 902 adds checks of whether the flame ignites all across the burner and of the gas solenoid valves, 903 is another shutdown, and 908 is the unit locked out, which Noritz says requires contacting the nearest Noritz agent rather than a power cycle.
Does it matter which Noritz you have?
EZ Series & NCC199CDV, NCC199 & NRC111, NR50, NR66 & NR71, NR98 & NR111 and NRC Series all route code 90 the same way: a professional, at $0–$1,000. 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 90, so they are safe to work through before you have identified your exact unit. They also cost nothing.
- Do not take any vent section apart yourself.
That is 1 of the 4 checks documented for code 90. 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 5 series that report code 90, the model number on the rating label starts EZ, NCC, GQ, N and NRC — match yours against the 43 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.
Source: Noritz Service Manual — NR501-OD, NR662-OD, NRC661, NRC711 (Rev. Dec 2013) (p. 28), read Sep 2026 — the manufacturer's own documentation for this Noritz range.
The same number on other brands
Code 90 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 90
Code 90 on these 5 Noritz series points at 4 parts and 2 symptoms, each named by the manufacturer's own procedure for this code.