Navien tankless water heater code E110: Abnormal air pressure (blocked vent or intake filter)

Canadian and US models

1. The intake air filter is clogged with dust or lint.

   Clean the intake air filter on a Navien NPE water heaterYou can do this

   1. Turn the heater off with the Power button, then unplug it, or switch it off at its power switch or breaker if it is wired in, and let it cool.
      Always disconnect the power before taking the cover off.
   2. Take off the heater's front cover, as Navien's manual describes for this job.
      Touch only the air filter. Leave every other part inside the heater alone.
   3. Undo the screw that holds the intake air filter (top left inside the heater) and pull the filter assembly out.
   4. Take the filter out of its plastic holder, clean it with a toothbrush under clean running water, and let it dry completely.
   5. Put the filter back in its holder, refit it with the screw, and replace the front cover.
   6. Plug the heater back in, or switch the power back on, and turn it on. Navien recommends cleaning this filter every 3 to 4 months.

   Clear a Navien error codeYou can do this

   1. Deal with the cause first, using the checks listed for the code.
   2. On NPE-A2 and NPE-S2 models, press the Back button on the front panel. On first-generation NPE-A and NPE-S models and on indoor NPN models, press the Reset button on the front panel.
   3. If an NR-21DU remote controller is fitted, you can press its OK button once instead. On outdoor NPN models, which have no front panel, the remote is the way to reset. The remote shows RST when the error is reset.
   4. If the code comes back, stop resetting. Note the code and the model number and contact Navien technical support or a licensed technician.
      Resetting over and over can hide a fault that needs a technician.

2. Something is blocking the exhaust vent pipe or its outside termination.

   Check the outside flue or vent terminal is clearYou can do this

   1. Find where the flue or vent pipe ends outside the building. High-efficiency furnaces and some water heaters also have a combustion air intake pipe beside it: check that one too. On some outdoor water heaters the flue outlet is part of the front cover.
   2. Look for anything blocking it, such as leaves, a bird or insect nest, snow, plants, or items stored against the wall.
   3. Cut back plants and move stored items away from it. Do not touch, poke into or hose the flue outlet. If something is inside it, book a service.
      The terminal can be hot. Do not climb onto the roof or use a ladder to reach it; if it is out of reach, book a technician.

   Book a licensed gas technician

3. A venting or air pressure problem that a technician needs to find. Suspect this when the code comes back with the filter clean and the vent clear.

   Book a licensed gas technician

US models

1. Something is blocking the vent pipe or its outside termination.

   Same check as above: Check the outside flue or vent terminal is clear

   Book a licensed gas technician

2. A venting or air pressure problem that a technician needs to find. Suspect this when the code comes back with the vent clear.

   Book a licensed gas technician

Booking a licensed gas technician