Navien NPN Installation & Operation Manual page 44

We recommend using a surge protector to
●
protect the water heater from power surges.
If there is a power failure in cold weather areas,
●
the freeze prevention system in the water heater
will not operate and may result in freezing of
the heat exchanger. In cold weather areas where
power failures are common, you must completely
drain the water heater to prevent damage if the
power will be off for any extended period of time.
A battery back-up (available at most computer
retailers) may be used to supply hot water during
periods of power outages. Damage caused by
freezing temperatures due to power loss is not
covered under warranty.
If you are not using your water heater for a long
period of time:
1. Completely drain the water out of the water
heater.
2. Disconnect the power supply to the water
heater. This prevents your water heater from
freezing and being damaged.
CAUTION
Label all wires before disconnecting them
when you work on the controls. Wiring errors
can cause improper and dangerous operation.
Verify proper operation after servicing.
Disconnect Switch (Outdoor Models
Only)
On outdoor models, there must be a disconnect
switch installed for the incoming 120 V AC power.
It should be designed to be suitable for outdoor
use. Make sure that you are in compliance with the
National Electrical Code, ANSI/NFPA 70, and your
local codes to ensure that you are using a proper
switch type for your area.
Installing the Water Heater 43