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Navien tankless water heater code E047: Exhaust temperature sensor fault

Tankless water heater, Canada and United States

The exhaust thermostat, which monitors exhaust temperature, is not operating normally.

This needs a licensed gas technician. There is nothing safe to check yourself. Leave the covers on and book a professional.

What causes it

NPE-A/S first-generation condensing models

  1. The exhaust thermostat or its wiring has failed. Navien lists no owner fix for this code.

    Book a licensed gas technician

NPE-A2/S2 condensing models

  1. The exhaust thermistor or its wiring has failed. Navien lists no owner fix for this code.

    Book a licensed gas technician

How to read this code on your unit

Booking a licensed gas technician

Contact Navien before booking a repairYou can do this

  1. Have the model number, serial number, purchase date, where the heater is installed and the error code ready.
  2. Call Navien Technical Support on 1-800-519-8794, or contact the company that installed the heater.
  3. For a repair under warranty, the installer or service provider must contact Navien before starting the work.

Book a licensed gas technicianlicensed gas technician

  1. Turn the unit off and leave the covers on. Gas components must only be serviced by a licensed technician.
  2. Note the code, how often it appears, and the model and serial numbers from the rating label.
  3. Book a licensed gas technician and give them those details.

Models that show this code

14 models in 4 ranges
RangeModels
NPE-A (first generation)NPE-180A, NPE-210A, NPE-240A
NPE-S (first generation)NPE-150S, NPE-180S, NPE-210S, NPE-240S
NPE-A2NPE-180A2, NPE-210A2, NPE-240A2
NPE-S2NPE-180S2, NPE-210S2, NPE-240S2, NPE-150S2

Where this comes from

Checked against the manufacturer's manual on 9 October 2026.

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Other Navien tankless water heater codes

Code Meaning What you can do
E016 Heat exchanger overheated Safe checks first, then a pro
E030 Exhaust too hot Safe checks first, then a pro
E031 Burner overheated Call a pro
E046 Limit control fault Call a pro
E056 Modulating gas valve fault Call a pro
E060 Dual venturi fault Call a pro
E109 Fan motor fault Safe checks first, then a pro
E407 Hot water outlet temperature sensor fault Call a pro
E421 Cold water inlet temperature sensor 1 fault Call a pro
E432 Cold water inlet temperature sensor 2 fault Call a pro
E441 Hot water inlet temperature sensor 2 fault Call a pro
E740 Outdoor temperature sensor fault Call a pro

See all temperature sensor fault codes on tankless water heaters across brands.