Navien NCB300-28K, Service Manual

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92 Replacement of Parts
6.2.12 DHW Heat exchanger
1. Turn off the gas supply to the unit.
2. Turn off the 230V power supply to the unit.
3. Turn off the water supply to the unit. Drain all water from
the appliance.
4. Remove the gas supply unit.
5. Remove the two screws at the DHW exchanger.
Figure 20
6. Replace with the new DHW Exchanger.
5. Remove the clip on the WPS valve.
Figure 19
6. Replace with new water pressure sensor.
7. Connect the water pressure senor wire housing.
Note
Always use proper O-rings at the water pressure
valve connection to ensure tight seals.