HVACopedia

Noritz · Tankless water heater

C1# Descaling reminder (C11-C19)

Low severity Noritz EZNoritz NRCR

What the control is telling you

Shown as C1 followed by a digit 1-9 when the descaling reminder (service reminder) is turned on and the set time has passed. It is a maintenance notice, not a failure. The reminder is off from the factory.

Applies to: Noritz EZ111/EZ98/EZ71 and NRCR111/NRCR92

Likely causes

  • Time to descale (worked out from burn time, average Btu use and set temp)

Test and repair steps

  1. Flush/descale the heat exchanger (see guide 'Descaling (flushing) the heat exchanger - Noritz').
  2. Also clean dust and lint from the fan and air intake; it affects combustion.
  3. Once the flush is done correctly the code clears.
  4. Water over 12 gpg hardness should be treated; damage from ignoring C1# is not covered by warranty.

Settings for these units

Save it for the next call

Star this code in the HVACopedia app and keep the whole library on your phone for jobs with no signal.

Open the app

Source: Noritz EZ/NRCR Owner's Guide (Rev. 10-25), Water quality and maintenance / error code C1#, p.28, 32; Noritz NRCR Pro training (NRCR92/NRCR111, Printable V3), Service reminder, p.31. Summarized in our own words; check the original manual for your model.

Homeowner looking at this code? See what it means for you and when to call a technician.

For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.