Navien NFC Series Guide

Getting Service
If your boiler requires service, you have several options for getting service:
●Contact Technical Support at 1-800-519-8794 or on the website: www.navien.com.
●For warranty service, always contact Technical Support first.
●Contact the technician or professional who installed your boiler.
●Contact a licensed professional for the affected system (for example, a plumber or electrician).
When you contact Technical Support, please have the following information at hand:
●Model number
●Serial number
●Date purchased
●Installation location and type
●Error code, if any appears on the front panel display.
800.519.8794 www.Navien.com
20 Goodyear lrvine, CA 92618
User’s Information Manual
NFC Condensing Combi-Boilers
THE LEADER IN CONDENSING TECHNOLOGY
Version: 1.0 (Nov 26, 2018)

WARNING
If the information in these instructions is not followed exactly, a fire or explosion may result, causing
property damage, personal injury, or death.
Do not store or use gasoline or other flammable vapors and liquids in the vicinity of this or any other
appliance.
WHAT TO DO IF YOU SMELL GAS
●Do not try to light any appliance.
●Do not touch any electrical switch; do not use any phone in your building.
●Immediately call your gas supplier from a neighbor’s phone. Follow the gas supplier’s instructions.
●If you cannot reach your gas supplier, call the fire department.
Installation and service must be performed by a qualified installer, service agency or the gas
supplier.
User’s Information Manual
NFC Condensing Combi-Boilers
Model
NFC-175
NFC-200
H
NSF/ANSI 372
Keep this manual near this boiler for future reference
whenever maintenance or service is required.
* The wetted surface of this product contacted by consumable water contains less than
one quarter of one percent (0.25%) of lead by weight.

2 Contents
Contents
1. Safety Information 3
2. About the Boiler 6
2.1 Description of the Boiler 6
2.2 Parts of the Boiler 6
2.3 The Front Panel 7
3. Operating the Boiler 9
3.1 Turning the Boiler On or Off 9
3.2 Adjusting the Temperature 9
3.3 Accessing Basic Menu Items 10
3.4 Resetting the Boiler 11
4. Maintaining the Boiler 12
4.1 Cleaning the Boiler 12
4.2 Draining the Boiler 12
4.3 Cleaning the Air Intake Filter 13
4.4 Protecting the Boiler from Freezing 15
4.5 Maintenance Schedules 15
5. Troubleshooting 20
5.1 Solving Basic Problems 20
5.2 Understanding Error Codes 21

Safety Information 3
WARNING
If you do not follow these instructions exactly, a fire or explosion
may result causing property damage, personal injury or loss of
life.
A. This appliance does not have a pilot. It is equipped with an
ignition device which automatically lights the burner. Do
not try to light the burner by hand.
B. BEFORE OPERATING smell all around the appliance area for
gas. Be sure to smell next to the floor because some gas is
heavier than air and will settle on the floor.
WHAT TO DO IF YOU SMELL GAS
●Do not try to light any appliance.
●Do not touch any electric switch; do not use any phone
in your building.
●Immediately call your gas supplier from a neighbor’s
phone. Follow the gas supplier’s instructions.
●If you cannot reach your gas supplier, call the fire
department.
●Do not return to your home until authorized by your
gas supplier or the fire department.
C. Do not use this appliance if any part has been under water.
Immediately call a qualified service technician to inspect
the appliance and to replace any part of the control system
and any gas control which has been under water.
The following safety symbols are used in this manual. Read and
follow all safety instructions in this manual precisely to avoid
unsafe operating conditions, fire, explosion, property damage,
personal injury, or death. Keep this manual for future reference.
DANGER
Indicates an imminently hazardous situation which, if not
avoided, could result in severe injury or death.
WARNING
Indicates a potentially hazardous situation which, if not
avoided, may result in injury or death.
CAUTION
Indicates a potentially hazardous situation that, if not avoided,
could result in property damage.
1. Safety Information

4 Safety Information
California law requires the following Prop 65 warning to be
provided:
WARNING
This product can expose you to chemicals including lead, lead
compounds, and carbon bisulfide which are known to the
State of California to cause cancer and birth defects or other
reproductive harm. For more information, go to
www.P65Warnings.ca.gov.
CAUTION
●Do not attempt to repair or replace any part of the boiler,
unless it is specifically recommended in this manual.
For all other service, contact an authorized technician or
licensed professional. Improper adjustments, alterations,
service, or maintenance may lead to property damage,
personal injury, or death and will void your warranty.
●Do not operate the boiler if you feel something is wrong
with it.
Doing so may result in product damage or personal injury.
●Do not allow children to operate or access the boiler.
Doing so may result in product damage or personal injury.
●Do not turn on the boiler unless the water and gas
supplies are fully opened.
Doing so may damage the boiler.
●Do not use this boiler for anything other than its
intended purpose, as described in this manual.
●Do not remove the front cover unless the power to the
boiler is turned off or disconnected.
Failure to do so may result in electric shock.
●When servicing the controls, label all wires prior to
disconnecting them.
Failure to do so may result in wiring errors, which can lead to
improper or dangerous operation.
●Do not use unapproved replacement or accessory parts.
Doing so may result in improper or dangerous operation
and will void the manufacturer’s warranty.
●Do not place anything in or around the vent terminals,
such as a clothes line, that could obstruct the air flow in
or out of the boiler.
●This boiler has been approved for use in the USA and
Canada only.
Using the boiler in any other country will void the
manufacturer’s warranty.
●Should overheating occur or the gas supply fail to shut
off, turn off the manual gas valve to the appliance.
WARNING
●Shut off the gas supply if the boiler is damaged.
Have your installer or plumber show you the location of the
gas shut off valve and demonstrate how to close the valve.
If the boiler is damaged as a result of overheating, fire, flood,
or any other reason, close the manual shut off valve and do
not operate the boiler again until it has been inspected by a
qualified technician.
●Do not store or use gasoline or other flammable liquids
near this boiler.
Doing so may result in fire or explosion.
●Do not place combustibles, such as newspapers or
laundry, near the boiler or venting system.
Doing so may result in a fire.
●Do not place or use hair sprays, spray paints, or any other
compressed gases near the boiler or venting system,
including the vent termination.
Doing so may result in fire or explosion.
●Do not operate the boiler with the front cover opened.
Doing so may result in fire or carbon monoxide (CO)
poisoning, which may result in property damage, personal
injury, or death.
●Do not operate this boiler without proper venting.
Doing so may result in fire or carbon monoxide (CO)
poisoning, which may result in property damage, personal
injury, or death. Inspect the vent termination and air intake
supply annually to ensure proper operation of the boiler.
Turn off and discontinue use of the boiler if any of the vent
pipes, vent elbows, or intake pipes are damaged in any way,
separated at a joint, or show evidence of corrosion, rusting,
or melting.
●Do not touch the power cord or internal components of
the boiler with wet hands.
Doing so may result in electric shock.
●Do not make any electrical connections before turning
off the electrical power supply at service entrance panel.
Doing so may result in severe personal injury or death.

Safety Information 5
DANGER
This boiler’s DHW water temperature is set to 120°F (49°C) at the
factory for your safety and comfort. Increasing the temperature
increases the risk of accidental scalding. Water temperatures at
or above 125°F (52°C) can cause instant scalding, severe burns,
or death. Before you decide to change the temperature setting,
read the following charts carefully.
Water
Temperature
Time in which a young child can suffer a
full thickness (3rd degree) burn
160°F (70°C) Less than 1 second
140°F (60°C) 1 second
130°F (55°C) 10 seconds
120°F (49°C) 10 minutes
100°F (37°C) very low scald risk
DANGER
HOT
BURN
To prevent burns:
●Use the lowest operating temperature setting necessary to
provide comfortably-hot water.
●If your household has children or elderly or disabled
residents, consider using a lower temperature setting.
●Read all the instructions in this manual carefully before
changing the temperature setting.
●Feel the water before using it on children, the elderly, or the
disabled.
●If it is necessary to set the water temperature above 125°F
(52°C), consider installing a thermostatically-controlled
mixing valve or temperature-limiting valve. Contact a
licensed plumber or your local plumbing authority for more
information.

6 About the Boiler
2.2 Parts of the Boiler
2.2.1 Front View
Exhaust
Gas Vent
Combustion
Air Intake
2.2.2 Bottom View
14.6” (370 mm)
2.6” (67 mm)
9.7” (247 mm)
5.2” (131 mm)
AD E
17.3” (440 mm)
8.5” (215 mm)
10.6“ (269 mm)
3.3” (85 mm) 5.4” (136.6 mm)
2” (53 mm)
3.4” (87 mm)
B C FG
#Description
AHeating Supply
BHot Water Outlet (DHW)
CCold Water Inlet (DHW)
DAuto Feeder Inlet (Make-up Water)
EHeating Return
FGas Connection
GCondensate Outlet
2.1 Description of the Boiler
The Navien NFC boiler is available in 2 models: NFC-175 and
NFC-200.
The main features are as follows:
●Power Interruption: When the power is restored after a power
failure, the boiler will automatically start and return to normal
operation. A manual reset is not required.
●Freeze Protection: A sensor inside the boiler automatically
detects the temperature and, if necessary, initiates a safety
heating cycle to prevent internal equipment damage due to
freezing temperatures.
●Short-Circuit Protection: Any short-circuit occurring in the
boiler’s electrical circuit immediately blows the internal glass
fuses and automatically cuts off the gas supply.
●Lightning Protection: Each boiler is specially grounded, both
internally and externally, to protect against lightning strikes.
●Carbon Monoxide Protection: The boiler is designed to maintain
a safe air-to-gas ratio and combustion rate. This function is
continuously monitored by the boiler’s air ratio control module.
●Auto Fan Detection: The rotation of the fan is automatically
detected and controlled. Fan failure will stop the operation of
the boiler.
●Boiling Prevention: Excessive temperatures will automatically
stop the boiler.
2. About the Boiler

About the Boiler 7
2.3 The Front Panel
The front panel allows you to adjust the temperature and view the operating status or error codes. Remove the protective sheet from the front
panel before using it.
2.3.1 Icons and Digital Display
The icons and digital display on the front panel provide important
information required for the boiler’s operation. Refer to the
following table for detailed information.
a
Outdoor reset
Displayed when the Outdoor Reset
feature is enabled.
bCombustion
Displayed when the burner is combusting.
c
System fault
Displayed when a system fault is
detected.
d
Anti-freeze
Displayed when the boiler is operating in
anti-freeze mode.
Auto air purge
Displayed when an auto air purge is being
performed.
e
Cascade/Main mode
Flashes when configuring a cascade
system. Turns on solid if the boiler
is set as the Main unit in a cascade
system.
f
DHW Operation
Displayed when the pre-heating feature is
activated.
●Always on ( ), Intelligent ( ),
Weekly ( ), Aquastat ( ), Manual ( )
g
Space heating demand
Indicates the space heating demands
from thermostats 1, 2, and 3.
hDHW demand
Indicates that DHW demand is present.
i
Space heating set temperature
Displays the currently set space
heating temperature.
j
DHW set temperature
Displays the currently set DHW
temperature.
kOutdoor temperature
Displays the outdoor temperature. l
System pressure
Displays the internal water pressure of the
boiler system.
b
a
d
f
c
g
i
k
h
j
l
e

8 About the Boiler
2.3.2 Buttons and Command Dial
Using the buttons and the Command dial on the front panel, you
can turn on or off the boiler, monitor the current operation status,
and set the values required for the boiler’s operation, such as space
heating and DHW supply temperatures. Refer to the following
table for detailed information.
aBack button
Return to the previous menu or screen, bMode button Enter the boiler’s main menu.
cPower button
Turn on or off the boiler. d
Command dial
Rotate to switch between menu items, or
to increase/decrease values.
Press to make a selection or to confirm
changes.
c
b
d
a

Operating the Boiler 9
2. Press the Command dial ( ) to select the space heating
temperature ( ). The highlighted section will flash.
3. Rotate the Command dial ( ) to the right or left to increase or
decrease the temperature.
4. Press the Command dial ( ) to confirm the new temperature.
5. Press the Back button ( ) to return to normal operation
mode, or rotate the Command dial ( ) to adjust other
operation conditions.
You can adjust the temperature while the highlighted section is
flashing. Once the flashing stops, the current temperature setting
is stored.
Note ●The space heating temperature cannot be adjusted
when the Outdoor Reset Control is used.
●The space heating temperature cannot be adjusted
if the boiler is operating as a sub unit in a cascade
system. The main unit’s set temperature will be
displayed on the screen.
●In case of outdoor reset sensor malfunction, the
boiler will operate at this set temperature.
●Take note of the original heating temperature in case
you want to restore it to the default.
●The default space heating supply water temperature
range is 104°F (40°C, Absolute MIN) to 180°F (82°C,
Absolute MAX).
●The default space heating return water temperature
range is 86°F (30°C, Absolute MIN) to 149°F (65°C,
Absolute MAX).
●You can adjust the temperature ranges in the
parameter settings menu.
●The boiler will retain your settings during a power
outage.
3.1 Turning the Boiler On or Off
To turn the boiler on or off, press the Power button.
When the power is on, the boiler automatically enters normal
operation mode, and the boiler’s operating conditions are
displayed on the screen.
Note The boiler status icons remain displayed when the
boiler is turned off.
3.2 Adjusting the Temperature
3.2.1 Adjusting the Space Heating Temperature
To adjust the heating temperature:
1. In normal operation mode, rotate the Command dial ( ) . The
space heating temperature ( ) is highlighted on the screen.
3. Operating the Boiler

10 Operating the Boiler
6. Press the Back button ( ) to return to normal operation
mode, or rotate the Command dial ( ) to adjust other
operation conditions.
You can adjust the temperature while the display is flashing. Once
the display stops flashing, the current temperature setting is
stored.
Note ●Take note of the original DHW indirect supply
temperature in case you want to restore it to the
default.
●The default DHW temperature range is 104°F (40°C,
Absolute MIN) to 180°F (82°C, Absolute MAX).
●You can adjust the temperature ranges in the
parameter settings menu.
●The boiler will retain your settings during a power
outage.
3.3 Accessing Basic Menu Items
In the Main Menu screen, you can view the boiler’s operating
conditions, configure the space heating and DHW temperatures,
and review error history. Press the Menu button ( ) to enter the
Main Menu screen.
To view information about the boiler, press the Menu button ( ),
and then select “2. Status Information”.
Rotate the Command dial ( ) to switch between the information
items. Press the Command dial ( ) to select an item and view the
information.
Press the Back button ( ) to exit information view mode.
3.2.2 Adjusting the DHW Indirect Supply
Temperature
To adjust the water temperature:
1. In normal operation mode, rotate the Command dial ( ) . The
space heating temperature ( ) is highlighted on the screen.
2. Rotate the Command dial ( ) to the right to select the DHW
temperature ( ).
3. Press the Command dial ( ) to select the indirect DHW
temperature ( ). The highlighted section will flash.
4. Rotate the Command dial ( ) to the right or left to increase or
decrease the temperature.
5. Press the Command dial ( ) to confirm the new temperature.

Operating the Boiler 11
Item Description
25. Outdoor Reset
Curve
Outdoor Reset Curve Load Type
(Displayed when the outdoor reset
option “20. Outdoor Reset”is enabled.)
1: Finned Tude Baseboard
2: FAN Coil
3: Cast Iron Baseboard
4: Low Mass Radiant
5: High Mass Radiant
6: Radiator
7: Custom (Set by installer.)
26. Boost Interval
Time Boost Interval Set Time (min)
27. High Altitude
Sea Level (0 - 2,000 ft)
Level 1 (2,000 - 5,400 ft)
Level 2 (5,400 - 7,700 ft)
Level 3 (7,700 - 10,100 ft)
28. Well Pump Well Pump Status
OFF - Unused, ON - Used
29. Model Model Type
30. Gas Fuel Type (NG/LPG)
31. Main F/W Ver Main Firmware Version
32. Panel F/W Ver Controller Panel Firmware Version
3.4 Resetting the Boiler
If an error message appears during boiler operation, reset the
boiler to resolve the problem. Press the Back button ( ) on the
front panel to reset the boiler.
If resetting the boiler does not solve the problem, refer to the
Troubleshooting section of this manual or contact Technical
Support at 1-800-519-8794.
Item Description
1. Operation State Current Operation State
2. Heat Capacity Heat Capacity (%)
3. SH Set Temp Space Heating Set Temperature (°F)
4. DHW Set Temp DHW Set Temperature (°F)
5. Supply Temp Heating Supply Temperature (°F)
6. Return Temp Boiler Return Temperature (°F)
7. Sys Supply Temp System Supply Temperature (°F)
8. Sys Return Temp System Return Temperature (°F)
9. Outlet 1 Temp Heat Exchanger Outlet Temperature (°F)
10. Outlet 2 Temp Outlet Temperature (°F)
11. Inlet Temp Inlet Temperature (°F)
12. Outdoor Temp Outdoor Temperature (°F)
13. Approx. Boiler
Flow SH Flow Rate (GPM)
14. DHW Flow DHW Flow Rate (GPM)
15. Water Press Water Pressure (psi)
16. Flame Value
Flame Detector AD Value
●Flame On: 8 bit AD Values equal to or
lower than 70
●Flame Off: 8 bit AD Values equal to or
higher than 175
17. Fan Target RPM Set Fan Speed (RPM)
18. Fan Current RPM Fan Speed (RPM)
19. Fan Target APS Set APS Voltage (V)
20. Fan Current APS APS Voltage (V)
21. Flow Control
Valve Status 100 - Close State
22. Mixing Valve
Status 0 - Close State
23. Exhaust Temp Exhaust Temperature (°F)
24. Outdoor Reset Outdoor Reset Status (Enable/Disable)

12 Maintaining the Boiler
4.1 Cleaning the Boiler
CAUTION
Make sure the boiler is turned off and the power supply is
disconnected before cleaning the boiler. The boiler may
remain hot for several minutes after it is turned off. To prevent
burns, wait until the boiler has cooled down before cleaning.
To clean the boiler, wipe the outside with a damp cloth. Use a non-
acidic, non-abrasive cleaner to remove any surface stains. The front
panel is moisture resistant, but it is not waterproof. Keep it as dry
as possible.
4.2 Draining the Boiler
You will need to drain the boiler before performing maintenance
tasks, such as to prevent the boiler from freezing when it will not
be used for an extended period.
Refer to “2.2 Parts of the Boiler” on page 6for details about part
locations.
To drain the boiler:
1. Place a bucket under the boiler to collect the residual water
inside the boiler.
2. Press the Power button on the front panel to turn off the boiler.
3. Close the gas valve.
Gas Valve
Open Closed
4. Close the water supply valve and the return valves on the
manifold system.
4. Maintaining the Boiler

Maintaining the Boiler 13
4.3 Cleaning the Air Intake Filter
If the air intake filter becomes clogged by dust or lint, the boiler
will cease to operate and“Error Code 110” will appear on the front
panel display. To properly maintain the boiler, clean the air intake
filter every 3-4 months.
To clean the air intake filter:
1. Press the Power button on the front panel to turn off the boiler.
2. Disconnect the power supply to the boiler.
3. Unfasten the 4 latches (2 at the top and 2 at the bottom) to
remove the front cover.
5. Remove the drain cap on the manifold system to drain the
boiler.
Drain Cap Drain Cap
Note ●Place a bucket under the boiler to gather water
released from the manifold system.
●Do not allow the pump to become wet.

14 Maintaining the Boiler
4. Remove the screw that secures the air intake filter (the filter is
located at the top left of the boiler).
5. Pull the filter out of the boiler.
6. Remove the filter from the plastic assembly. Dust and rinse it
with clean running water.
7. Allow the filter to dry completely.
8. Place the filter assembly back into the boiler and secure it with
the screw.
9. Replace the front cover.
10. Reconnect the power supply to the boiler.
11. Press the Power button on the front panel to turn on the boiler.

Maintaining the Boiler 15
4.5 Maintenance Schedules
Owner maintenance
Daily
●Check the boiler area is free of
combustible/flammable materials and
air contaminants.
●Check the pressure/temperature
gauge for signs of higher than normal
pressure.
Monthly
●Visually inspect the vent piping for
signs of leakage and blockage.
●Visually inspect the burner flames.
●Inspect the condensate trap and the
PVC fittings.
Periodically ●Test the LWCO for proper operation.
Every 6 months
●Inspect boiler piping (gas and water)
for leaks.
●Test to make sure the relief valve is
operating normally.
Non-heating
season
●Shut boiler down (unless boiler is used
for domestic hot water).
Service technician (See the following instructions)
Annual Start-up
General:
●Address reported problems.
●Inspect interior; clean and vacuum if
necessary.
●Clean condensate trap and fill with
fresh water.
●Check for leaks (water, gas, flue,
condensate).
●Verify flue and air lines in good
condition and sealed tight.
●Check system water pressure/system
piping/expansion tank.
●Check control settings.
●Check ignition and flame rod (clean and
reposition).
●Check wiring and connections.
●Inspect flame (stable, uniform).
●Inspect flame signal.
If combustion or performance indicate
need:
●Flush heat exchanger.
●Remove and clean air intake filter.
●Remove and clean space heating
strainer.
●Remove and clean inlet water filter.
4.4 Protecting the Boiler from Freezing
CAUTION
Damage due to freezing is not covered by the Navien limited
warranty.
●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.
●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.
●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.
●The boiler is designed for indoor installation only.
To ensure that the boiler does not freeze, follow these guidelines:
●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.
●Do not close the gas valve, except for routine maintenance, as
this will limit additional freeze protection.
●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.
Note ●If hot water will not flow and you suspect that the
boiler is frozen, contact an authorized technician or
licensed professional.
●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.

16 Maintaining the Boiler
Cleaning the Condensate Trap
1. Inspect the condensate drain line, condensate fittings, and
condensate trap.
2. Remove any sediment in the trap.
3. Fill with fresh water until the water begins to pour out of the
drain.
Checking all Piping for Leaks
Eliminate all system or boiler leaks. Continual fresh makeup water
will reduce boiler life. Minerals can build up in sections, reducing
heat transfer, overheating heat exchanger, and causing heat
exchanger failure. Leaking water may also cause severe property
damage.
1. Inspect all water and gas piping and verify to be leak free.
2. Look for signs of leaking lines and correct any problems found.
Checking the Flue Vent System and Air Piping
1. Visually inspect the entire flue gas venting system and air
piping for blockage, deterioration or leakage. Repair any
joints that show signs of leakage. Verify that air inlet pipe is
connected and properly sealed (if installed).
2. Verify that boiler vent discharge and air intake are clean and
free of obstructions.
WARNING
Failure to inspect for the above conditions and have them
repaired can result in severe personal injury or death.
WARNING
●Follow the service and maintenance procedures given
throughout this manual and in component literature
shipped with the boiler. Failure to perform the service and
maintenance could result in damage to the boiler or system.
●Failure to follow the directions in this manual and
component literature could result in severe personal injury,
death, or substantial property damage.
●The boiler should be inspected annually only by a qualified
service technician. In addition, the maintenance and care
of the boiler must be performed to assure maximum boiler
efficiency and reliability. Failure to service and maintain the
boiler and system could result in equipment failure.
●Electrical shock hazard – Turn off power to the boiler
before any service operation on the boiler except as noted
otherwise in this instruction manual. Failure to turn off
electrical power could result in electrical shock, causing
severe personal injury or death.
Addressing the Reported Problems
Inspect any problems reported by the owner and correct before
proceeding.
Inspecting the Installation Area
1. Verify that boiler area is free of any combustible materials,
gasoline and other flammable vapors and liquids.
2. Verify that air intake area is free of any of the contaminants
listed in Installation & Operation Manual. If any of these are
present in the boiler intake air vicinity, they must be removed.
If they cannot be removed, reinstall the air and vent lines per
the Installation and Operation Manual.
Inspecting the Boiler Interior
1. Remove the front cover and inspect the interior of the boiler.
2. Vacuum any sediment from inside the boiler and components.
Remove any obstructions.

Maintaining the Boiler 17
Checking the Water System
1. Verify all system components are correctly installed and
operational.
2. Check the cold fill pressure for the system. Verify it is correct
(must be a minimum of 12 psi).
3. Watch the system pressure as the boiler heats up (during
testing) to ensure pressure does not rise too high.
Note ●If the system contains glycol, test for proper
concentration as recommended by manufacturer.
●Excessive pressure rise indicates expansion tank
sizing or performance problem.
4. Inspect automatic air vents and air separators. Remove air vent
caps and briefly press push valve to flush vent.
5. Replace caps. Make sure vents do not leak. Replace any leaking
vents.
Checking Expansion Tank
●Expansion tanks provide space for water to move in and out as
the heating system water expands due to temperature increase
or contracts as the water cools.
●Perform annual checks as recommended by manufacturer to
ensure proper operation.
Checking the Pressure Relief Valves
1. Inspect the relief valve and lift the lever to verify flow. Before
operating any relief valve, ensure that it is piped with its
discharge in a safe area to avoid severe scald potential.
Note Safety relief valves should be inspected at least once
every three years, by a licensed plumbing contractor
or authorized inspection agency, to ensure that the
product has not been affected by corrosive water
conditions and to ensure that the valve and discharge
line have not been altered or tampered with illegally.
WARNING
●Certain naturally occurring conditions may corrode the
valve or its components over time, rendering the valve
inoperative. Such conditions are not detectable unless
the valve and its components are physically removed and
inspected. This inspection must only be conducted by a
plumbing contractor or authorized inspection agency – not
by the owner. Failure to re-inspect the boiler relief valve
as directed could result in unsafe pressure buildup, which
can result in severe personal injury, death, or substantial
property damage.
●Following installation, the valve lever must be operated at
least once a year to ensure that waterways are clear. Certain
naturally occurring mineral deposits may adhere to the valve,
rendering it inoperative. When manually operating the lever,
water will discharge and precautions must be taken to avoid
contact with hot water and to avoid water damage.
●Before operating lever, check to see that a discharge line
is connected to this valve directing the flow of hot water
from the valve to a proper place of disposal. Otherwise
severe personal injury may result. If no water flows, valve is
inoperative. Shut down the boiler until a new relief valve has
been installed.
2. After following the above warning directions, if the relief
valve weeps or will not seat properly, replace the relief valve.
Ensure that the reason for relief valve weeping is the valve and
not over-pressurization of the system due to expansion tank
waterlogging or undersizing.
Inspecting the Ignition and Flame Detector Electrodes
1. Remove the ignition and flame detector electrodes from the
boiler heat exchanger.
2. Remove any deposits accumulated on the ignition/flame
detector electrode. If the electrodes cannot be cleaned
satisfactorily, replace with new ones.
3. Replace ignition/flame detector electrode, making sure gasket
is in good condition and correctly positioned.

18 Maintaining the Boiler
Checking the Ignition Ground Wiring
1. Check that the ground wire is in good condition and securely
attached to the boiler casing.
2. Check ground continuity of wiring using continuity meter.
3. Replace ground wires if ground continuity is not satisfactory.
Checking all Boiler Wiring
Inspect all boiler wiring, making sure wires are in good condition
and securely attached.
Checking the Control Settings
1. From the front panel, enter the State Data Information mode
and check all settings. Adjust settings if necessary.
2. Check settings of external limit controls (if any) and adjust if
necessary.
Performing Start-up and Checks
1. Start boiler and make sure that the boiler is operating properly.
2. Verify cold fill pressure is correct and that operating pressure
does not go too high.
Check the Burner Flame
1. Inspect flame through observation window.
2. If the flame is unsatisfactory at either high fire or low fire, check
for obstructions in the venting and ensure that the air intake
filter is clean.
Review with the Owner
1. Review the User’s Information Manual with the owner.
2. Emphasize the need to perform the maintenance schedule.
3. Remind the owner of the need to call a licensed contractor
should the boiler or system exhibit any unusual behavior.
4. Remind the owner to follow the proper shutdown procedure
and to schedule an annual start-up at the beginning of the
next heating season.
Flushing the Heat Exchanger
CAUTION
Flushing the heat exchanger is a somewhat complicated
procedure. Read the following instructions carefully before
attempting this procedure. If you are uncertain about any of
the steps in the procedure, contact an authorized technician or
licensed professional. Keep in mind that improper maintenance
can void your warranty.
Refer to the“2.2 Parts of the Boiler”on page 6for details about
part locations.
Before flushing the Heat Exchanger, gather the following items:
●A bucket that is 5 gallons or larger
●Cleaning solution diluted with water
●3 hoses
●A water circulation pump
●2 flush valves (if not installed)
Note Before flushing the heat exchanger, additional flush
valves (“A” and “B”) must be installed on the near boiler
piping (included with Navien Manifold System).
A
CB
D

Maintaining the Boiler 19
7. Pour the cleaning solution into the bucket.
8. Open both “A” and “B” valves.
9. Turn on the circulation pump and allow the solution to
circulate through the boiler. Refer to the manufacturer’s
literature for information about the circulation time.
10. Rinse the cleaning solution from the boiler:
a. Remove the free end of the drain tube from the bucket and
place it in the condensate drain or laundry tub (wherever
the boiler drains).
b. Close the“B” valve and open the“D” valve. Do not open the
“D” valve yet.
c. Allow water to flow through the boiler for 5 minutes.
d. Close the “A”valve and open the “C” valve.
11. Disconnect all tubes and valves.
12. Reconnect the power supply to the boiler.
13. Press the Power button on the front panel to turn on the boiler.
To flush the Heat Exchanger:
A
B
C
D
Flushing Kit
Circulation Pump
Cold Water Supply
Hot Water Line
Navien
Manifold
System
1. Press the Power button on the front panel to turn off the boiler.
2. Disconnect the power supply to the boiler.
3. Close the “C” and “D”valves on the supply and return water
lines.
4. Connect one tube to the “A”valve and place the free end in the
bucket.
5. Connect one of the tubes to the circulation pump outlet and
the return water line at the“B”valve.
6. Connect one tube to the circulation pump inlet and place the
free end in the bucket.