Navien NFC-175, Руководство по обслуживанию

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NFC Service Manual 117 Version 1.0
5.2.35 777 & 031Error
No. Error code Cause Check method
8
777
LWCO
(Decompression
transformer
error)
When LWCO signal
is detected to Open
more than five
seconds, the system
determines that
there is no water
in the boiler and
piping, stops the
ignition and pump,
and outputs a LWCO
error message.
1. If a LWCO sensor is not equipped,
(1) Check the controller connection terminal.
When a LWCO sensor is not equipped, there is a terminal connecting the two holes
in the controller. An error can occur if the terminal is not connected completely.
(2) Check the decompression transformer harness.
If the problem persists after completing (1), check if the settlement of the
controller connector is right or it is disconnected.
(3) Change the decompression transformer.
If the problem persists after completing (1) and (2), change the decompression
transformer.
(4) Change the PCB.
If the problem persists after completing all the actions above, change the PCB.
2. If a LWCO sensor is equipped,
(1) Check pipe leakage.
If decompression failed, an error occurs. Check if there is a leakage in the heating
line.
(2) Check if the LWCO sensor harness is disconnected.
If the problem persists after completing (1), check if the LWCO sensor harness is
disconnected.
(3) Change the LWCO sensor.
If the problem persists after completing (1) and (2), change the LWCO sensor.
(4) Change the decompression transformer.
If the problem persists after completing (1), (2), and (3), change the decompression
transformer.
(5) Change the PCB.
If the problem persists after completing all the actions above, change the PCB.
Decompression transformer
Check the connection
of the decompression
transformer harness.
Check the terminal
connection status