HVACopedia

Noritz · Tankless water heater

12 Flame loss (repeated)

High severity Noritz EZNoritz NRCRNoritz CDVNoritz NRC/NRCP

What the control is telling you

The burner lit but the flame went out and could not be held. Like code 11, low inlet gas pressure is a main cause. Same meaning on premix (EZ/NRCR/CDV) and non-premix (NRC/NRCP) units; only the allowed gas pressure range differs.

Applies to: All Noritz residential tankless (EZ, NRCR, NCC199CDV, NRC/NRCP)

Likely causes

  • Inlet gas pressure too low under load (undersized gas line or meter)
  • Dirty or poorly positioned flame rod
  • Bad ground connections
  • Incorrect venting (exhaust recirculating or blocked)

Test and repair steps

  1. Measure inlet gas pressure with the unit at full fire and other appliances running. Premix (EZ, NRCR, NCC199CDV) inlet gas: NG 3.5-10.5 in. WC, LP 8-14 in. WC. NRC/NRCP inlet gas: up to 199k Btu/h NG 4-10.5 in. WC, LP 8-14 in. WC; over 199k Btu/h NG 5-10.5 in. WC, LP 10.5-14 in. WC.
  2. Remove, check and clean the flame rod (fine abrasive pad or 300+ grit sandpaper).
  3. Check and tighten ground connections at the board and chassis.
  4. Inspect the venting for wrong materials, poor termination or blockage; the deck shows incorrect venting as a cause.
  5. If the gas line is undersized, resize it per the installation manual gas tables (see Specs).
  6. If still flame loss, contact Noritz technical support (866-766-7489).

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Source: Noritz EZ/NRCR/CDV Level 2 Maintenance & Troubleshooting (Premix R2 V2), 12 error code, p.13; Noritz Residential Level 2 Maintenance & Troubleshooting (NRC/NRCP and older, R2 V1), 12 error code, p.7; Noritz NRCR Pro training (NRCR92/NRCR111, Printable V3), Gas line conditions, p.20. 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.