Navien NHB H Series Installation And Operation Manual page 71

If you are not using your boiler for a long period of
time:
1. Completely drain the water out of the boiler.
2. Disconnect the power supply to the boiler.
This prevents your boiler from freezing and being
damaged.
WARNING
Electric Shock Hazard
To prevent serious injury or death:
ALWAYS label all wires before disconnecting
●
them when you work on the controls.
Wiring errors can cause improper and
●
dangerous operation.
ALWAYS verify proper operation after
●
servicing.
Connecting the Power Supply 71