Noritz Error Code 90: Combustion abnormality (Tankless)
Noritz error code 90 on a tankless water heater means: Combustion abnormality. It is also called Noritz diagnostic code 90.
Homeowner? What Noritz code 90 means for you
Call a technician Your tankless water heater is reporting: Combustion abnormality. The tankless water heater has locked out or cannot run properly. One reset is fine; if the code comes back, it needs a licensed technician to find the cause.
Safe things you can check yourself
- Check that gas reaches the house: other gas appliances work, or the propane tank is not empty.
- Make sure the heater is plugged in and its breaker is on. In winter, keep the power on: it protects the unit from freezing.
- Outside, make sure the intake and exhaust pipes or vent cap are not blocked by snow, ice, leaves or a nest.
- Check that the hot and cold water valves under the heater are fully open.
- If you have a remote controller, turn it off and on once. If the code comes back, call a technician.
Call (647) 657-2977Book a service call
Licensed technicians serving Vaughan, Toronto and the GTA.
What does Noritz error code 90 mean?
On EZ/NRCR/CDV (premix): the unit cannot reach set temperature, most often from restricted intake/exhaust, wrong DIP/vent settings, a clogged condensate drain, low gas pressure, or on older units a dirty fan/venturi. On NRC/NRCP (non-premix): two main causes, not reaching set temperature and/or the fan speed over-correcting (MM49 above 100) because of air restriction. Owner's guide shows 901 and 902 with the same meaning.
Applies to: All Noritz residential tankless (EZ, NRCR, NCC199CDV, NRC/NRCP)
Common causes of Noritz code 90
- Blocked or restricted intake or exhaust (lint, debris, animals, bad termination)
- Wrong DIP switch / vent settings
- Clogged or frozen condensate drain line (premix)
A technician checks these and 3 other possible causes on site before replacing any part.
Noritz models that use code 90
EZ71DVEZ98DVEZ111DVN-0841MCN-0841MC-DVN-0842MCN-0842MC-DVNCC199CDVNRC111-DVNRC111-SVNRCR92DVNRCR111DV
Other Noritz Tankless codes
All Noritz Tankless Water Heater error codes →
Noritz code 90: homeowner questions
What does Noritz code 90 mean?
Combustion abnormality. On EZ/NRCR/CDV (premix): the unit cannot reach set temperature, most often from restricted intake/exhaust, wrong DIP/vent settings, a clogged condensate drain, low gas pressure, or on older units a dirty fan/venturi. On NRC/NRCP…
Is it safe to keep using my tankless water heater with code 90?
It depends on the cause. The tankless water heater has locked out or cannot run properly. One reset is fine; if the code comes back, it needs a licensed technician to find the cause.
Can I reset Noritz code 90 myself?
You can try one reset (power off for 30 seconds, then on). If Noritz code 90 comes back, the cause is still there and a licensed technician should check it.
Who can fix Noritz code 90 near me?
Aurora Star Tech Inc. repairs Noritz tankless water heaters in Vaughan, Toronto and across the GTA. Call (647) 657-2977 or book a service call online.
Homeowner help: Tankless Water Heater No Hot Water: What to Check
Troubleshooting guides
- No hot water All brands · Tankless Water Heater
- Water temperature fluctuates All brands · Tankless Water Heater
- Cleaning ignition and flame rods - Noritz Noritz · Tankless Water Heater
- Cleaning the fan and burner - Noritz EZ/NRCR/CDV Noritz · Tankless Water Heater
- Descaling (flushing) the heat exchanger - Noritz Noritz · Tankless Water Heater
- Draining to prevent freezing - Noritz EZ/NRCR Noritz · Tankless Water Heater
- Field gas conversion NG to LP - Noritz NRCR/EZ Pro Noritz · Tankless Water Heater
- Heat exchanger replacement - Noritz NRC111 / NCC199 Noritz · Tankless Water Heater
- Heater does not fire when hot water is opened - Noritz tankless Noritz · Tankless Water Heater
- Recirculation not working or hot water slow - Noritz NRCR Noritz · Tankless Water Heater
- Water not hot enough or temperature fluctuates - Noritz tankless Noritz · Tankless Water Heater
Source: Noritz EZ/NRCR/CDV Level 2 Maintenance & Troubleshooting (Premix R2 V2), 90 error code and MM31/MM32, p.16-17, 20-21; Noritz Residential Level 2 Maintenance & Troubleshooting (NRC/NRCP and older, R2 V1), 90 error code and MM49, p.10-11, 15; Noritz NRCR Pro training (NRCR92/NRCR111, Printable V3), Gas line conditions, p.20; Noritz EZ/NRCR Owner's Guide (Rev. 10-25), Checking for error conditions, p.31. Written in our own words as a summary; always check the original manual.
General guidance for qualified technicians. The manufacturer's installation and service manual and local codes always take priority. Aurora Star Tech is not affiliated with, endorsed by or sponsored by any equipment manufacturer; brand and model names are used only to identify equipment and belong to their owners.