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Noritz · Tankless water heater

73 Circuit board setting abnormality

Low severity Noritz EZNoritz NRCRNoritz CDVNoritz NRC/NRCP

What the control is telling you

DIP switches or connectors were changed while the unit had power. On premix units it also shows when a replacement board was installed but not programmed.

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

Likely causes

  • DIP switches or connectors changed with power on
  • Replacement circuit board not programmed (premix)

Test and repair steps

  1. Unplug the unit.
  2. Finish all DIP switch and wiring changes with the power off.
  3. Plug the heater back in and check that the code clears.
  4. Premix with new board program the board (EZ Start Plus app or built-in display) for model, gas type and venting.

Settings for these units

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Source: Noritz EZ/NRCR/CDV Level 2 Maintenance & Troubleshooting (Premix R2 V2), 73 & F76 error codes, p.15; Noritz Residential Level 2 Maintenance & Troubleshooting (NRC/NRCP and older, R2 V1), 73 & F76 error codes, p.9. 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.