Navien NCB-180, Service Manual

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108 NCB Service Manual Version 1.0
5.2.16 407Error
Error conditions and Check Items
Error Description
E407
Hot water outlet
thermistor open or
short
If an error (open: 14°F (-10°C) or lower) in the DHW Outlet Elbow input temperature sensor is detected,
the system displays the 407E error on the front panel.
Check items
1. Check if the hot water temperature sensor connector is wet due to any reason and if the connector is
connected properly..
2. Check if the temperature sensor is open or short
Is the DHW outlet
thermistor normal?
Resistance between #5 and #6 of CN13 is from
0.437k
Ω
to 176k
Ω
at normal condition.
(see page56 for Wiring Diagram)
Check connector
(#5 and #6 of CN 13)
Replace the DHW outlet
thermistor
Before measuring resistance of the thermistor,
detach the connector from the PCB.
NO
Yes