Noritz tankless water heater code 20
Your series decides which reading applies. Across the 5 Noritz series documented here, code 20 is listed as high limit switch triggered (4 series) and heat exchanger high limit switch triggered (1 series). Find your series in the table below, where those readings route to a professional.
What code 20 means on each Noritz series
| Series | What it means | Verdict | Typical cost |
|---|---|---|---|
| EZ Series & NCC199CDV | Heat exchanger high limit switch triggered | Call a pro | $100–$900 |
| NCC199 & NRC111 | High limit switch triggered | Call a pro | $150–$900 |
| NR50, NR66 & NR71 | High limit switch triggered | Call a pro | $150–$900 |
| NR98 & NR111 | High limit switch triggered | Call a pro | $150–$900 |
| NRC Series | High limit switch triggered | Call a pro | $150–$900 |
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 20 — 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 20 agree and where they part company.
EZ Series & NCC199CDV — Heat exchanger high limit switch triggered
The high limit switch on the primary heat exchanger has tripped. Noritz's checks are whether the switch triggered, whether it is properly connected, and then one line that is worth the whole entry: check if there is scale build-up in the heat exchanger, because this error code may be caused by it. Noritz does not say that about any other code in this table.
NCC199 & NRC111 — High limit switch triggered
A high limit switch has tripped. Two details make this entry different from the same number on other Noritz ranges. Noritz prints a note against it — this model has two kinds of high limit switch — so which one tripped is itself part of the diagnosis. And the third check is whether the exhaust gas temperature is too high, which pulls the flue into a code that elsewhere is purely about water.
NR50, NR66 & NR71 — High limit switch triggered
The high limit switch has tripped. Noritz's checks are whether the switch is triggered and whether it is improperly connected, and the power has to be cycled to clear the code. Four flashes on an NR71 or N-0631S with no remote controller.
NR98 & NR111 — High limit switch triggered
The high limit switch has tripped. Noritz's checks on this range are short: whether the switch is triggered, and whether it is improperly connected. It is the safety device that stops the unit when the water gets too hot, so it sits downstream of everything that can overheat the appliance.
NRC Series — High limit switch triggered
The high limit switch has tripped. This is the safety device that stops the unit when the water gets too hot, and Noritz's checks are whether it has actually triggered and whether it is properly connected. It sits downstream of everything that can overheat the appliance, so it is the symptom rather than the cause.
Does it matter which Noritz you have?
EZ Series & NCC199CDV, NCC199 & NRC111, NR50, NR66 & NR71, NR98 & NR111 and NRC Series all route code 20 the same way: a professional, at $100–$900. That makes it one of the Noritz numbers you can act on before working out which unit you own.
Which Noritz do you have?
On the 5 series that report code 20, 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.
Parts, guides and symptoms behind code 20
Code 20 on these 5 Noritz series points at 3 guides, 3 parts and 2 symptoms, each named by the manufacturer's own procedure for this code.