Noritz tankless water heater code 21
Your series decides which reading applies. Across the 2 Noritz series documented here, code 21 is listed as burner chamber high limit switch triggered (1 series) and pressure switch triggered (1 series). Find your series in the table below, where those readings route to a professional.
What code 21 means on each Noritz series
| Series | What it means | Verdict | Typical cost |
|---|---|---|---|
| EZ Series & NCC199CDV | Burner chamber high limit switch triggered | Call a pro | $250–$1,500 |
| NR98 & NR111 | Pressure switch triggered | Call a pro | $200–$1,200 |
Each row opens the full page for that generation. We hold manuals for EZ Series & NCC199CDV and NR98 & NR111, and each one gets its own reading of code 21 — what Noritz documents, what you can safely check yourself, and what the repair should cost.
What each manual actually says
The table above compares 2 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 2 readings of code 21 agree and where they part company.
EZ Series & NCC199CDV — Burner chamber high limit switch triggered
The second high limit switch — the one in the burner chamber — has tripped. Noritz checks whether it triggered, whether it is properly connected, and whether the burner chamber is clogged or damaged. The remark is the important part: to reset this error code, contact the nearest Noritz agent. Unlike code 20, cycling the power will not clear it.
NR98 & NR111 — Pressure switch triggered
Noritz restricts this code explicitly: for NC380-SV-ASME and N-1321M-ASME only. If your unit is an NR98, NC199, NR111 or NC250, this number is not on your table at all. The checks are the pressure switch itself, the fan motor, the flue for blockage or obstruction, and abnormal combustion.
How much the answer changes between series
EZ Series & NCC199CDV and NR98 & NR111 all route code 21 the same way: a professional, at $200–$1,500. That makes it one of the Noritz numbers you can act on before working out which unit you own.
The spread is real money. On the NR98 & NR111 the worst case is $1,200; on the EZ Series & NCC199CDV the same number can reach $1,500. That is a $300 gap behind one number.
Which Noritz do you have?
On the 2 series that report code 21, the model number on the rating label starts EZ, NCC, GQ, NR and NC — match yours against the 23 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. 56), read Sep 2026 — the manufacturer's own documentation for this Noritz range.
The same number on other brands
Code 21 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 21
Code 21 on these 2 Noritz series points at 4 parts and 3 symptoms, each named by the manufacturer's own procedure for this code.