Noritz NRC Series Code CF
Scale lockout. The unit has locked itself out after repeated scale warnings. Noritz's wording is that the unit is locked because of a repeated scale build-up error code, that the heat exchanger must be flushed, and that you should contact Noritz America for more information before flushing it. The display window appends a digit. This is the end of the road that code C1 was warning about.
Also displayed as: CF1, CF2, CF3, CF4
Call a proThe verdict
Call a licensed plumber
Unlike C1, this one is not a job to start on your own — Noritz asks to be contacted before the heat exchanger is flushed at this stage, and the lockout needs clearing as well as the scale. Expect a conversation about whether the heat exchanger survived.
Typical cost: $200–$1,500
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
- Do not start a flush before contacting Noritz America or a Noritz agent — that is their own instruction for this code specifically.
- Have the model number and the unit's age to hand; whether the heat exchanger is still under warranty changes the conversation.
- Book a professional flush and lockout reset.
Frequently asked questions
Why does Noritz want to be called before a CF flush when C1 says just flush it?
Because by CF the appliance has been running scaled for a long time. A flush at that point can dislodge deposits that were doing structural work, and Noritz wants to establish the state of the heat exchanger first. It is also the point at which a warranty claim, if there is one, gets decided.