21Error - Navien NP-180 Service Manual

5.12. 21Error

Error occurrence conditions and check items.
Error
If an error (open: -10
21E
Heat exchanger
is detected, the system displays the 21E error message on the remote controller
input
and the PCB.
temperature
The boiler maintains the Safety-Shutdown status.
sensor open
1. Check if the heat exchanger input temperature sensor connector is wet due to
any reason, including leakage.
Check items
2. Replace the defected heat exchanger input temperature sensor.
3. Replace the PCB.
Check method
Error
Defective
temperature sensor
connector
Defective
sensor
Temperature
Defective
Other trouble
<Heat exchanger input temperature sensor /
connector, Black 2P>
©Navien America Inc. 2010
Description
or lower) in the heat exchanger input temperature sensor
Cause
Check if the temperature sensor is open and if the connector is
connected properly.
Check the resistance of the temperature sensor.
(Defective if it is 30
Replace the temperature sensor if the resistance value is abnormal.
sensor
Check the temperature displayed on the PCB. (C.10.0 10.0 ).
If the trouble continues despite the checking of above items,
replace the PCB.
PCB
95
NR/NP series service Manual
Check method
or higher)
<Check if the hot water temperature sensor is open>
Error type : MΩ Open
Version 2.0