The Error Code 90 indicates an airflow or combustion abnormality.
(Error Code 10 is also troubleshot with the same methods)
To simplify it, the unit is either struggling to move air in or out of the unit or it is unable to hit the set temperature.
For a newly installed tankless unit showing a 90 error code, the problem could be due to one of the following reasons:
- The gas supply’s calorific value is too low
- Insufficient gas pressure
- Incorrect venting installation
- Improper condensate drain installation
- Incorrect unit settings for elevation, vent pipe size, or length
On a unit that has been installed for some time and only recently exhibits the 90 error code, it could still be related to the above but more likely attributed to a dirty unit due to lack of maintenance or the condensate drain line might be clogged.
Inlet Gas Pressures:
The inlet gas pressure to the unit needs to stay between the minimum and maximum gas pressures listed below under all situations. When completing an installation it’s a good practice to run the unit at low, medium and high flow rates along with other gas appliances at the jobsite while monitoring the inlet pressure with a manometer to ensure it’s always above the minimum.
Check Venting and Termination Installation:
Make sure venting and terminations are all within the allowable size and length as stated in the installation manual. Make sure terminations are clean of any debris.
Check Unit Settings:
Make sure the unit is programmed properly with the EZ Start Plus App or by using the built in display. Incorrect unit settings could result in combustion abnormalities.
For further technical assistance call 866-766-7489 or use our Contractor Locator to find a local service representative.