Noritz tankless water heater code 59
Heat exchanger flow fault. Code 59 means the same thing on all 3 Noritz series documented here — but the fix, and what it costs, is still worth reading for your exact unit.
What code 59 means on each Noritz series
| Series | What it means | Verdict | Typical cost |
|---|---|---|---|
| NCC199 & NRC111 | Heat exchanger flow fault | DIY fix | $40–$900 |
| NR50, NR66 & NR71 | Heat exchanger flow fault | DIY fix | $40–$900 |
| NR98 & NR111 | Heat exchanger flow fault | DIY fix | $40–$900 |
Each row opens the full page for that generation. We hold manuals for NCC199 & NRC111, NR50, NR66 & NR71 and NR98 & NR111, and each one gets its own reading of code 59 — what Noritz documents, what you can safely check yourself, and what the repair should cost.
What each manual actually says
The table above compares 3 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 3 readings of code 59 agree and where they part company.
NCC199 & NRC111 — Heat exchanger flow fault
Noritz puts scale first in the remedy for this one: check for scale build-up in the heat exchanger, then abnormal combustion, then the flue for blockage or obstruction, then that the flame ignites all the way across the burner. It is the closest thing this series has to a dedicated descaling code, and Noritz notes that it does not appear in the manual's own troubleshooting flowchart.
NR50, NR66 & NR71 — Heat exchanger flow fault
Noritz puts scale first: check for scale build-up in the heat exchanger, then abnormal combustion, then the flue for blockage or obstruction, then that the flame ignites all the way across the burner. Noritz notes the code does not appear in the manual's own flowchart. On a unit with no remote controller it shows as continuous flashing, and Noritz records that the heater is available to burn even before you reset it.
NR98 & NR111 — Heat exchanger flow fault
Noritz puts scale first: check for scale build-up in the heat exchanger, then abnormal combustion, then the flue for blockage or obstruction, then that the flame ignites all the way across the burner. Noritz notes that this code does not appear in the manual's own troubleshooting flowchart.
Does it matter which Noritz you have?
NCC199 & NRC111, NR50, NR66 & NR71 and NR98 & NR111 all route code 59 the same way: a descale, at $40–$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 59, so they are safe to work through before you have identified your exact unit. They also cost nothing.
- Flush the heat exchanger — our descaling guide covers it end to end.
- If the code survives a proper flush, book a service call rather than flushing again.
- Afterwards, work out your water hardness and set a flushing interval from it.
That is 3 of the 4 checks documented for code 59. 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 3 series that report code 59, the model number on the rating label starts NCC, N, NRC, NR and NC — match yours against the 30 listed below. You can also use the full model-number decoder.
Where this comes from
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.
Parts, guides and symptoms behind code 59
Code 59 on these 3 Noritz series points at 3 guides, 2 parts and 3 symptoms, each named by the manufacturer's own procedure for this code.