Navien tankless water heater code E438: Circulation pump fault

NPE-A/S first-generation condensing models

1. A shutoff valve on the water supply or recirculation return line is closed.

   Check the recirculation lines and pump on a Navien water heaterYou can do this

   1. If the heater runs an external recirculation loop, find the supply and return pipes for the loop and check that any shutoff valves on them are fully open.
   2. On NPE-A2 and NPE-S2 models installed with an air handler or a separate circulation pump, check that the pump has power and is running.
   3. On NPE-A models with internal recirculation, the direction of the 2-way valve is a check for your installer.
   4. Reset the heater. If the code comes back with the valves open and the pump powered, book a technician.

   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. With internal recirculation, the 2-way valve may be set to the wrong position. Navien's manual lists checking its direction; leave this check to your installer.

   Book a licensed plumber

3. If the code returns after the checks above, contact Navien technical support or a qualified technician to investigate the circulation pump.

   Book a licensed gas technician

NPE-A2/S2 condensing models

1. The circulation pump that serves the air handler is not running properly.

   Same check as above: Check the recirculation lines and pump on a Navien water heater

   Same check as above: Clear a Navien error code

2. The pump or its wiring has failed. Suspect this when the pump has power and the code comes back.

   Book a licensed gas technician

NPN non-condensing models

1. With external recirculation, a shutoff valve on the recirculation supply or return line is closed.

   Same check as above: Check the recirculation lines and pump on a Navien water heater

   Same check as above: Clear a Navien error code

2. The pump or its wiring has failed. Suspect this when the lines are open and the code comes back.

   Book a licensed gas technician

Booking a licensed gas technician