Noritz EZ Series & NCC199CDV Code C1
Service reminder. The unit's service reminder, shown as C1 through C9. Noritz names two things it is reminding you about, and most write-ups only mention the first: excessive scale build-up, which may cause premature failure of the heat exchanger, and excessive dust or lint build-up in the fan and air intake, which may affect efficiency and combustion performance. It is a warning indication — the unit keeps working.
Also displayed as: C2, C3, C4, C5, C6, C7, C8, C9, F C1
DIY fixThe verdict
Descale the unit
The cheapest thing in this table to act on. A flush plus a clean air intake is an afternoon and the price of a descaling kit; the heat exchanger it protects is most of what the appliance is worth. Do both — Noritz names the air side as well as the water side, and the dust half is usually skipped.
Typical cost: $40–$400
US estimate for parts and labor. Prices vary by region and by who does the work — see how we estimate costs.
What the manual says
The meaning above is transcribed from the manufacturer's diagnostic documentation for the EZ Series & NCC199CDV — not averaged across the brand.
Source: Noritz Service Manual — NRC663 FSV, EZ98DV, EZ111DV, NCC199CDV (Rev. Oct 2017) (p. 32), read Sep 2026 — the manufacturer's own documentation for this exact series.
What you can safely check
- Flush the heat exchanger — our descaling guide covers the process end to end.
- Clean the dust and lint out of the fan and air intake as well; Noritz names it in the same reminder and it is the half most people miss.
- If the unit has no isolation valves, have them fitted while someone is there — without them every future flush needs a plumber.
- Work out your water hardness and set an interval from it, rather than waiting for the reminder each time.
Frequently asked questions
Is the service reminder based on how scaled the unit actually is?
Not directly. It is a reminder, not a measurement — the unit counts operating hours and prompts you. That is why hardness matters more than the calendar: in hard water the reminder can arrive later than the scale does, and in soft water earlier than you need it.
Does this code stop the unit?
No. Noritz labels C1# a warning indication and the heater keeps running. That is the difference between this series and the NRC table, where the scale codes escalate to a shutdown and then to a CF lockout.
Code C1 on other Noritz series
The same code number can mean something different on another series — make sure you're reading the page for your exact unit: