Noritz NRC Series Code 99
Combustion fault, unit locked. Combustion abnormality with the unit locked out. Noritz's checks are abnormal combustion and the flue for blockage or obstruction, and the remark is unambiguous: to reset this error code, contact the nearest Noritz agent. Unlike the 90x family, cycling the power will not clear it.
Call a proThe verdict
Call a licensed plumber
The appliance has taken itself out of service over combustion and will not let you put it back. That is not a fault in the lockout — it is the design working. Nothing here is a homeowner job.
Typical cost: $200–$1,200
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 NRC Series — not averaged across the brand.
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 exact series.
What you can safely check
Before anything else: if you smell gas, stop here, leave, and call your gas utility.
- Leave the unit off.
- Contact a licensed professional or a Noritz agent — Noritz requires an agent to clear this lockout, and cycling the power will not do it.
Code 99 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: