Error Code 91

EC91 or Error Code 91

An error code 91 means incorrect gas type.

For new installs:

  1. Verify the unit is provided the correct gas type.
  2. Verify the unit is installed according to the guidelines found in the installation manual either included with the unit for downloaded from our support site here: http://support.noritz.com/technical-literature.php

For existing installations:

  1. Verify the unit is provided the correct gas type.
  2. Verify the unit is installed according to the guidelines found in the installation manual either included with the unit for downloaded from our support site here: http://support.noritz.com/technical-literature.php
  3. Verify that the manifold gas pressures are correctly set. This should be done by a service rep according to the service manual for the unit.
  4. Perform a cleaning of the fan, burner and heat exchanger fins if there is dust, dirt, lint or other debris building up.

For further help with the error code 91, please contact technical support at 866-766-7489.

Updated on April 12, 2021

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