NFC Service Manual 121
Version 1.0
6.1 Replacement Procedure
CAUTION
1. When performing maintenance and/or servicing the
boiler, always turn off the electric power, gas and water
shut-off valve. Wait for the boiler to become cool. Be
careful to avoid injury to your fingers on sharp edges.
2. Drain all water from the boiler when removing the
waterway components.
3. Before any disassembly, make sure that all issues and error
codes are properly diagnosed.
4. Handle all parts carefully.
5. When reassembling, prevent any foreign substance, i.e.
dust, etc. from entering back into the boiler.
6. After reassembling, check for gas and water leakage.
Then, test for proper ignition. Make sure that there is no
gas leakage from the gas connections by testing with
soap bubble solution. Bubbles indicate a gas leak that
must be corrected.
7. Check the performance and operation after the boiler has
been serviced.
To remove and replace any parts from the boiler, you will need
a screwdriver that is at least 8 ~ 10 inches long. A flashlight and
magnetic tip are also recommended. Navien recommends the use
of a parts tray to hold small parts and screws. All of the hardware is
essential to the proper operation of the unit upon re-assembly.
Note
When disassembling and reassembling the boiler, refer
the components diagram & parts list.
6.2 Components Replacement Instructions
6.2.1 PCB
1. Turn off the gas supply to the unit.
2. Disconnect the unit from the power supply.
3. Turn off the water supply to the unit.
4. Disconnect wiring connector from the Front Panel.
Figure 1
5. Disconnect all wiring connectors from the PCB and remove the
4 screws from bottom PCB bracket and upper PCB bracket.
Figure 2
6. Remove the old PCB and replace it with the new part.
7. Reattach all wiring connectors to the PCB.
8. Set the proper DIP S / W settings on the PCB.
9. Reinstall the PCB and Front Panel using the 7 screws previously
removed.
10. Turn on the water and gas supplies, then reconnect the power
supply to the unit.
Note
All wiring harness connections to the PCB should
match in color and pin types. Do not use excessive
force when removing the connectors as this may cause
damage to the PCB.
6. Replacement of Parts
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