438Error ("A" Models Only) - Navien NPE-180A Service Manual

5.1.15 438Error ("A" models only)

Error occurrence conditions and check items
Error
Connect the power, start the pump, and check if the system senses water flow.
E438
If flow is not sensed after the pump has started, the system displays 438E (cleared automatically) on the front
Pump error
panel.
1. Defective flow sensor.
2. Defective pump.
* Check water filter for debris.
Check items
* Check for locked air in the pump.
3. Defective PCB.
* Check the operation of the pump and flow sensor using the Component Test mode (refer to page 47).
Panel Test operation mode
(PUMP operation)
Is there cold water
supply inside water
heater?
Yes
Is the circulation pump
operating normally?
Yes
Check water flow sensor
NO
Supply cold water to the water
heater.
NO
Is the pump operating
at normal voltage?
Yes
Check the PUMP resistance
Description
NO
Check the voltage #1 and #3 of CON2: 97 - 138VAC
(see page 52 for Wiring Diagram)
Reset the unit
Troubleshooting 105