Navien NBH Series, User'S Information Manual

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Maintaining the Boiler 15
If hot water will not flow and you suspect that the boiler is frozen,
follow these steps:
1. Press the Power button on the front panel to turn off the boiler.
Close the gas valve.
Gas Valve
Open Closed
2. Open the hot water faucet that is closest to the boiler.
3. Use a hair dryer or a portable electric heater to heat up both
the primary and secondary Heat Exchangers.
4. Check every few minutes to see if water is running at the open
faucet.
5. When the water starts flowing again, check the boiler and
piping for leaks. If you detect any leaks or the boiler is not
operating properly, contact an authorized technician or
licensed professional.
Note
This boiler requires very little maintenance, however
a qualified technician should inspect the boiler at the
beginning of every heating season and/or when there
is a problem.
CAUTION
If the unit will not be used immediately, close off all gas and
water shutoff valves, drain all of the water out of the unit and
the plumbing system to prevent the unit and system from
freezing, and bleed the gas out of the gas line.
4.4 Protecting the Boiler from Freezing
CAUTION
Damage due to freezing is not covered by the Navien limited
warranty.
Ɣ
Freezing damage is most likely to occur due to back drafting
caused by negative pressure in the building. This is not a
manufacturing defect, and therefore, Navien will not warrant
any damages due to freezing. The installer is responsible for
ensuring that there is sufficient make-up air to avoid such
a situation and the owner is responsible for ensuring that
protection against freezing is maintained.
Ɣ To avoid freezing issues, we strongly recommend the use of
a direct vent exhaust and intake system. Your installer should
ensure that the exhaust vent pipe and the air intake pipe are
both connected directly from the collars on the top of the
boiler to the outdoors. This type of vent system minimizes
air movement within the boiler.
Ɣ This boiler has an optional recirculation mode that is used for
freeze protection. This mode should prevent the boiler from
freezing, even if the intake air duct is not vented directly.
Ɣ
The boiler is designed for indoor installation only.
To ensure that the boiler does not freeze, follow these guidelines:
Ɣ
Do not unplug the power supply cord, except for routine
maintenance. The boiler has a freeze protection function that
requires electricity. The freeze protection function will operate
regardless of whether or not the power is turned on or off, as
long as the electric supply is still connected.
Ɣ
Do not close the gas valve, except for routine maintenance, as
this will limit additional freeze protection.
Ɣ
If the boiler will not be used for an extended period, drain
the boiler.
If the power or gas supplies must be disconnected for an
extended period, drain the boiler. Freezing damage may occur if
there is water remained in the boiler in cold weather.