001Error - Navien NHB-055 Service Manual

5.2.1 001Error

Error occurrence conditions and check items
Error
E001
Overheating of Heat
Exchanger
Check items
Verify thermistor readings at
the front panel. Is the supply
Verify checkpoints under Check Items list
Version 1.0
1. In order to prevent boiling in the heat exchanger, if the space heating water temperature is
higher than 216°F(102°C), E001 will be displayed on the front panel
2. If the space heating water temperature decreases below than 216°F(102°C), E001 will be
automatically reset and the unit will repeat the combustion cycle.
3. If overheating occurs three (3) times consecutively, E001 will be displayed and must be
manually reset.
1. Check the circulation pump (external) operating status. Run Pump Test Mode.
2. Check if filter (strainer of the heating pipe is clogged.
3. Check if the main heat exchanger is clogged.
4. Check the heating inlet / outlet valve and distribution piping for any obstructions.
5. Check the PCB DIP S / W capacity setting.
6. Check if the PCB is operating properly..
7. If the issues continue despite checking the items above, replace the PCB.
8. Check if Air Purge is fully done in the system. (If Air Vent is opened?)
thermistor normal?
Yes
Description
No
Replace the supply thermistor
Resistance between #7 and #8 of CN13 is from
0.437kΩ to 176kΩ at normal condition.
(see page 63-64 for Wiring Diagram)
Before measuring resistance of the thermistor,
detach the connector from the PCB.
NHB Service Manual 83