Navien NFC-250/175H User manual

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.
WHATTO 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.
The installation must conform with local codes or, in the absence of local codes, the
National Fuel Gas Code, ANSI Z223.1/NFPA 54 and/or CSA B149.1, Natural Gas and Propane
Installation Code.
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.
Installation Manual
NFC-H Condensing Combi-Boilers
Model NFC-250/175H
NFC-250/200H
H
NSF/ANSI 372

2
Requirements for the State of Massachusetts
NOTICE BEFORE INSTALLATION
This appliance must be installed by a licensed plumber or gas fitter in accordance with the Massachusetts
Plumbing and Fuel Gas Code 248 CMR Sections 4.00 and 5.00.
IMPORTANT: In the State of Massachusetts (248 CMR 4.00 & 5.00)
For all side wall horizontally vented gas fueled equipment installed in every dwelling, building or structure used
in whole or in part for residential purposes, including those owned or operated by the Commonwealth and
where the side wall exhaust vent termination is less than seven (7) feet above finished grade in the area of the
venting, including but not limited to decks and porches, the following requirements shall be satisfied:
1. INSTALLATION OF CARBON MONOXIDE DETECTORS. No installation or replacement of a vented gas appliance
shall be permitted unless a battery powered or electrically hard wired carbon monoxide detector is present
on the same floor as the appliance or on the next adjacent floor when the appliance is located in a crawl
space unless the appliance is located in a detached, uninhabitable garage. For all residential dwellings, a
carbon monoxide detector must also be present on each habitable level of the dwelling. These requirements
shall not be deemed to waive any additional requirements imposed by M.G.L. c. 148 §26F1/2.
2. APPROVED CARBON MONOXIDE DETECTORS. Each carbon monoxide detector as required in accordance
with the above provisions shall comply with NFPA 720 and be ANSI/UL 2034 listed and IAS certified.
3. SIGNAGE. Whenever any through-the-wall vent is installed less than seven feet above the finished grade,
a metal or plastic identification plate shall be permanently mounted to the exterior of the building at a
minimum height of eight feet above grade directly in line with the exhaust vent terminal. The sign shall
read, in print size no less than 0.5 inches in size,“GAS VENT DIRECTLY BELOW. KEEP CLEAR OF ALL
OBSTRUCTIONS”.
4. INSPECTION. The state or local gas inspector of the side wall horizontally vented gas fueled equipment shall
not approve the installation unless, upon inspection, the inspector observes carbon monoxide detectors and
signage installed in accordance with the provisions of 248 CMR 5.09 and 5.12.

3Contents
8. Installing a Cascade System 82
8.1 Connecting Water Supplies 82
8.2 Cascade System - Recirculation System
Application Example 84
8.3 Connecting the Communication Cables 86
9. Installing a Common Vent System 88
9.1 About the Common Vent System 88
9.2 Navien Common Vent Collar Kit (Back-
draft Damper) 93
9.3 Starting the Common Vent System 94
9.4 Connecting and Terminating the Vent
Pipe 98
9.5 Setting up the Common Vent System 99
9.6 Common Vent Termination Clearances 99
9.7 Installing a Condensate Drain 101
9.8 Maintenance 102
10. Installation Checklist 103
11. Operating the Boiler 106
11.1 Operating the Boiler for the First Time 106
11.2 Turning the Boiler On or Off 107
11.3 Start-Up Wizard 108
11.4 Adjusting the System Temperatures 109
11.5 Accessing Basic Menu Items 110
11.6 Accessing Advanced Menu Items 118
11.7 Understanding Error Codes 127
12. Appendixes 129
12.1 Gas & High Altitude Conversion 129
12.2 Wiring Diagram 137
12.3 Ladder Diagram 138
12.4 Outdoor Temperature Sensor 139
12.5 Outdoor Reset Control 139
12.6 Component Assembly Diagrams and
Parts Lists 141
1. About the Boiler 7
1.1 Included Items 7
1.2 Accessories 7
1.3 Specifications 8
1.4 Components 11
1.5 Dimensions 13
1.6 Rating Plate 14
2. Installing the Boiler 15
2.1 Removing the Wood Pallet from the boiler15
2.2 Choosing an Installation Location 16
2.3 Mounting the Boiler to the Wall 18
3. Installing the System Piping 20
3.1 Installing a Space Heating System 20
3.2 Installing a Domestic Hot Water (DHW)
System 26
3.3 Connecting the Condensate Drain 28
3.4 Filling the System 32
3.5 Testing the Water System 33
3.6 Considerations for System Applications 34
3.7 Examples of Electrical Connections 45
4. Connecting the Gas Supply 56
4.1 Gas Pipe Sizing Tables 59
4.2 Measuring the Inlet Gas Pressure 60
5. Venting for Combustion Air 62
5.1 Venting the Boiler 63
5.2 About the Vent Installation Detector 65
5.3 Selecting a Vent Type 68
5.4 Selecting Vent Pipe Materials 73
5.5 Measuring Vent Length 74
5.6 Terminating the Vent 75
6. Setting the DIP Switches 79
6.1 DIP Switch 1 (Set of 6 Switches) 79
6.2 Dip Switch 2 (Set of 8 Switches) 80
7. Connecting the Power Supply 81
Contents

4Safety Information
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.
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, could result in injury or
death.
CAUTION
Indicates a potentially hazardous situation that,
if not avoided, could result in property damage.
DANGER
If you smell gas:
●Do not try to light any appliance.
●Do not touch any electrical switches or use
landline phones.
●From a neighbor’s phone, call your gas
provider and follow their instructions.
●If you cannot reach your gas provider, call the
fire department.
●Do not return to your home until authorized
by your gas supplier or the fire department.
Do not use or store flammable products,
such as gasoline, solvents, or adhesives in
the same room or area as the boiler.
●The boiler has a main burner flame that can
turn on at any time and can ignite flammable
vapors. Vapors from flammable liquids can
explode and catch fire, causing death or
severe burns.
●Vapors cannot be seen and are heavier than
air. They can travel long distances along the
ground and can be carried from other rooms
to the boiler’s main burner flame by air
current.
●Keep all flammable products far away from
the boiler and store them in approved
containers. Keep the containers closed tightly
and out of the reach of children and pets.
Safety Information

5Safety Information
California law requires the following Prop 65
warning to be provided:
WARNING
Cancer and Reproductive Harm -
www.P65Warnings.ca.gov.
CAUTION
●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. Verify proper operation after
servicing.
●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.
WARNING
●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.
●Do not touch the power cord or internal
components of the boiler with wet hands.
Doing so may result in electric shock.

6Safety Information
DANGER
This boiler’s DHW 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.
●Do not leave children, the elderly, or disabled
persons unsupervised.
●Do not allow small children to play
unsupervised in the bathroom.
●Do not allow anyone to change the water
temperature while hot water is running.
●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.

7About the Boiler
1.1 Included Items
When you open the box, you will find the following
items with the boiler. Check the box for each of the
following items before installing the boiler.
Installation & Operation
Manual, User’s
Information Manual
Quick Installation Manual
2 in Vent Termination
Caps (x2) 2 in Wall Flanges (x4)
Air Vent Wall Mounting Bracket
Tapping Screws &
Anchors (x2)
Pressure Relief Valve,
Heating
Propane Conversion Kit*
High Altitude Conversion Kit
(Natural Gas Only)*
Outdoor Temperature
Sensor and Cable
Air Vent Bushing
(3/4in to 1/2in)
Condensate Trap Universal Temperature
Sensor
Spare Parts
* High Altitude Conversion kit and Propane Conversion kit
are attached to the inside of Product’s cover.
1.2 Accessories
The following optional accessories are available for
the boiler.
Condensate Neutralizer
Kit
Zone Controller
(FMZ-40/60)
Zone Controller
(FMZ-20/30)
Universal Temperature
Sensor (with clip)
Navi-Link
(Wi-Fi Control System) Ready-Link Rack
Navien Manifold System NaviClean
HotButton Push Button HotButton Wall Plate
Note The Universal Temperature Sensor can
be used as a System Temperature Sensor
or a DHW Tank Sensor.
1. About the Boiler

8About the Boiler
1.3 Specifications
The following tables list the specifications for the boiler. Additional specifications for water, gas, electricity, and
vent connections are provided in the Installation section.
Space Heating Specifications
Navien Condensing Boiler
Space Heating Ratings Other Specifications
Model
Number
1
Heating
Input (MBH) Heating
Capacity
2
(MBH)
Net AHRI
Rating Water
3
(MBH)
AFUE
2
(%)
Water
Pressure
Water
Connection Size
(Supply, Return)
Water
Volume
Min Max
NFC-250/175H 13.3 175 161 140 95 6–80 psi 1 in NPT 4.5
gallons
NFC-250/200H 199 183 159 95
Note 1. Ratings are the same for natural gas models converted to propane use.
2. Based on U.S. Department of Energy (DOE) test procedures.
3. The net AHRI water ratings shown are based on a piping and pickup allowance of 1.15. Consult
Navien before selecting a boiler for installations having unusual piping and pickup requirements,
such as intermittent system operation, extensive piping system, etc.
Domestic Hot Water Specifications
Item NFC-250/175H NFC-250/200H
Input Ratings Min 13,300 BTU/H 13,300 BTU/H
Max 210,000 BTU/H 210,000 BTU/H
Water Pressure 15-150 psi
Minimum Flow Rate 0.5 GPM (1.9 L/m)
Flow Rate 45°F (25°C) Temp. Rise 7.9 GPM
DHW Supply Connection Size
3
/
4
in NPT
Cold Water Input Connection Size
3
/
4
in NPT

9About the Boiler
NFC-H Internal Pump
The NFC-H boiler is equipped with an internal circulation pump. The following table provides detailed
information on the pump used for the boiler and the performance curve.
Item Pump Model
NFC-250/175H, NFC-250/200H
Internal Recirculation Pump
Grundfos UPS 15-78 CIAO2
(Part Number: 30023987A)
0
5
10
15
20
25
30
0
2
4
6
8
10
12
14
16
0 2 4 6 8 10 12 14 16
FT of Head
△P (psi)
Flow Rate (GPM)
NFC-250/175H, NFC-250/200H Grundfos Circulator Sp3 (Default) Grundfos Circulator Sp2 Grundfos Circulator Sp1
NFC-H Flow Performance Curve
0
5
10
15
20
25
30
35
40
45
01234567891011
△P (psi)
Flow Rate (GPM)
NFC DHW Pressure Drop Curve
NFC-H DHW Pressure Drop Curve

10 About the Boiler
General Specifications
Item NFC-250/175H NFC-250/200H
Dimensions 17.3 in (W) x 17.3 in (D) x 33.5 in (H)
Boiler Weight 141 lb (64 kg)
Boiler Weight with Water 170 lb (77 kg)
Installation Type Indoor Wall-Hung
Venting Type Forced Draft Direct Vent
Ignition Electronic Ignition
Natural Gas Supply Pressure (from source) 3.5 in–10.5 in WC
Propane Gas Supply Pressure (from source) 8.0 in–13.0 in WC
Natural Gas Manifold Pressure -0.03 to -0.92 in WC
Propane Gas Manifold Pressure -0.02 to -0.77 in WC
Flow Rate
(DHW)
35°F (19°C) Temp Rise 10.4 GPM (39.5 L/m)
45°F (25°C) Temp Rise 7.9 GPM (30.0 L/m)
67°F (37°C) Temp Rise 5.4 GPM (20.3 L/m)
Gas Connection Size
3
/
4
in NPT
Power Supply
Main Supply 120V AC, 60Hz
Maximum Power
Consumption Less than 15 amperes
Materials Casing Cold-rolled carbon steel
Heat Exchangers Stainless Steel
Venting
Exhaust
2 in or 3 in PVC, CPVC, approved polypropylene*
2 in or 3 in Special Gas Vent Type BH (Class III, A/B/C)
2 in or 3 in Stainless Steel
Intake
2 in or 3 in PVC, CPVC, polypropylene
2 in or 3 in Special Gas Vent Type BH (Class III, A/B/C)
2 in or 3 in Stainless Steel, ABS
Vent Clearance 0 in to combustibles
Safety Appliances
Flame Rod, APS, Ignition Operation Detector
Water Temperature High Limit Switch, Exhaust Temperature
High Limit Sensor, Water Pressure Sensor, Burner High Limit
Fuse, Vent Installation Detector (VID)
Temperature Setting Range
Item Temperature Setting Range Remarks
Space
Heating
Supply 77–185°F (25-85°C) Actual supply and return
temperatures vary depending
on the selected outdoor reset
curve.
Return 68–158°F (20-70°C)
DHW 86°F-140°F (30°C-60°C)
Note For more information about the space heating temperature setting range, refer to“11.5.2 Setting the
Space Heating Operation” on page 112.

11About the Boiler
1.4 Components
The following diagram shows the key components of the boiler. Component assembly diagrams and particular
parts lists are included in the Appendixes.
Intake Air
Air Intake Pipe
Vent Installation
Detector
Exhaust
Duct
Fan & Motor
Assembly
Dual Venturi
APS
PCB
Power Switch
PRV-Air Vent
Connection
Gas Pipe
Mixing Chamber
Igniter
Flame Rod
Igniter Transformer
Fire-Tube Type
Heat Exchanger
ASME Name Plate
Front Panel
Gas Valve
Condensate Outlet
24V Power
Transformer
Gas Inlet
Condensate Trap
(Siphon)

12 About the Boiler
Terminal Block
Dual Venturi
Fan & Motor Assembly
Igniter Transformer
Fire-Tube Type
Heat Exchanger
APS
Power Switch
Mixing Valve
3-Way Valve
Heating Return
Gas Valve
ASME Name Plate
Mixing Chamber
Intake Air Filter
Flame Rod
Igniter
Circulation Pump
Water Adjust Valve
DHW Exchanger
Water Fill Valve
Heating Supply
DHW Inlet
DHW Outlet
Condensate Trap
(Siphon)
PCB
Front Panel
Gas Pipe
Air Intake Pipe

13About the Boiler
1.5 Dimensions
The following diagrams show the dimensions of the boiler and the table lists the supply connections.
33.5"(850mm)
43.3"(1,100mm)
35.5"(901mm)
Supply Connections
Description Diameter
AAir Intake 2 in
BExhaust Gas Vent 2 in
CPRV-Air Vent Connection
3
/
4
in
DHeating Supply 1 in
EHeating Return 1 in
FGas Connection
3
/
4
in
GCondensate Outlet
1
/
2
in
HCold Water Inlet (DHW)
3
/
4
in
IHot Water Outlet (DHW)
3
/
4
in
JAuto Feeder Inlet (Make-up Water)
1
/
2
in
Overhead View
AB
C
3.8”(97mm)
4.3”(109mm)
4.1”(105mm)
9.7”(246mm)
17.3”(440mm)
Supply Connections
14.6”(370mm)
2.6”(67mm)
9.7”(247mm)
5.2”(131mm)
DJ E
17.3”(440mm)
8.5”(215mm)
10.6“(269mm)
3.3”
(85mm)
2”
(53mm)
I H FG
5.4”
(136.6mm)
5.4”
(136.6mm)
3.4”
(87mm)

14 About the Boiler
1.6 Rating Plate
The Navien NFC-H boilers come from the factory configured for use with Natural Gas (NG). Before starting
the installation, check the rating plate located on the side of the boiler to ensure that the boiler matches the
gas type, gas pressure, water pressure, and electrical supply available in the installation location. If the boiler
does not match each of these ratings, do not install the boiler. If conversion to Propane Gas is required, the
included gas conversion kit must be used. Refer to“12.1 Gas & High Altitude Conversion” on page 129 for details.
WARNING
Ensure that the gas type and power source specifications match what is listed on the rating plate. Using a
different gas type will cause abnormal combustion and boiler malfunction. Using abnormally high or low AC
voltage may cause abnormal operation, and may reduce the life expectancy of the product.
This appliance complies with the requirements of SCAQMD Rule 1146.2 for NOx emissions of 14 ng/J or 20 ppm
at 3% O
2
.

15Installing the Boiler
2.1 Removing the Wood Pallet
from the boiler
After you open the box, remove the wood pallet and
the pallet brackets and then install the boiler.
CAUTION
After opening the box, verify that all included
accessories are present in the accessory box and
upper container.
Removing the Wood Pallet and the
Pallet Brackets
1. Loosen the six screws that secure the wood
pallet on the bottom left and right sides of the
boiler.
2. Remove the accessory box, the wood pallet, the
upper container, and the lower pad.
Upper
Container
Lower
Pad
Wood
Pallet
3. Loosen the six screws that secure the pallet
brackets.
2. Installing the Boiler

16 Installing the Boiler
2.2 Choosing an Installation
Location
When choosing an installation location, you must
ensure that the location provides adequate clearance
for the boiler, adequate venting and drainage
options, and sufficient access to gas, water, and
electrical supplies. Carefully consider the following
factors when choosing an installation location:
Compliance Requirements
●Local, state, provincial, and national codes, laws,
regulations, and ordinances.
●National Fuel Gas Code, ANSI Z223.1-latest edition.
●Standard for Controls and Safety Appliances for
Automatically Fired Boilers, ANSI/ASME CSD-1,
when required.
●National Electrical Code.
●For Canada only: B149.1 Installation Code, CSA
C22.1 Canadian Electrical Code Part 1, CSA-B214-12
Installation code for hydronic heating systems, and
any local codes.
Access to Utilities
●Water – the installation location should be near
where the domestic water supply enters the building.
●Gas – the installation location should be near where
the gas supply enters the building.
●Electricity – the installation location should be near
where the electrical supply enters the building.
Humidity and Contact with Water
When installing the boiler, avoid places with
excessive humidity. The boiler has electric gas
ignition components. Moisture can get inside
the boiler and damage the ignition system. The
boiler must be installed in a way to ensure that
the gas ignition system components are protected
from water (dripping, spraying, rain, etc.) during
operation and service.
CAUTION
Keep the removed screws in a safe place. The
screws will be used again in Step 5.
4. Remove the two pallet brackets.
5. Tighten the six screws into the original position.
CAUTION
Ensure that the screws have been retightened
so that the boiler can maintain a proper airtight
seal.

17Installing the Boiler
Proximity to Fixtures and Appliances
Install the boiler near fixtures that deliver or use
hot water, such as bathroom, kitchen, and laundry
room faucets. Select a location that minimizes the
water piping required between major fixtures. If the
distances are long or if the user desires shorter wait
times for hot water, installation of a recirculation
line which circulates domestic hot water back to the
boiler from the furthest fixture is recommended.
Insulate as much of the hot water supply and
recirculation lines as possible. For more information
about the water supply, refer to“3.2 Installing a
Domestic Hot Water (DHW) System” on page 26.
Adequate Drainage
The boiler produces a significant amount of
condensate during operation. The boiler should be
located near a suitable drain and where damage
from a possible leak will be minimal. Installing the
boiler in a location without a drain will void the
warranty and Navien will not be responsible for
water damages that occur as a result. For more
information about condensate drainage, refer to“3.3
Connecting the Condensate Drain”on page 28.
The boiler must be located in an area where leakage
of the unit or connections will not result in damage
to the area adjacent to the appliance or to lower
floors of the structure. When such locations cannot
be found, installation of an adequately drained drain
pan under the boiler is highly recommended. When
installing the drain pan, ensure that the installation
does not restrict combustion air flow.
Adequate Venting and Ventilation
Select a location that requires minimal venting.
Consider venting restrictions caused by windows,
doors, air intakes, gas meters, foliage, and other
buildings. For more information about venting, refer
to“5. Venting for Combustion Air”on page 62.
To ensure adequate venting and ventilation, follow
these guidelines:
●Maintain proper clearances from any openings in
the building.
●Ensure that the vent termination is at least 12 in
(300 mm) above ground, 12 in (300 mm) above
the highest anticipated snow level, or as required
by local codes, whichever is greater.
●Do not enclose the vent termination.
●Install the exhaust vent in an area that is free
from any obstructions, where the exhaust will not
accumulate.
●Do not install the boiler where moisture from the
exhaust may discolor or damage walls.
●Do not install the boiler in bathrooms, bedrooms,
or any other occupied rooms that are normally
kept closed or not adequately ventilated.

18 Installing the Boiler
Clean, Debris and Chemical-free Combustion Air
●Do not install the boiler in areas where dust and
debris may accumulate or where hair sprays,
spray detergents, chlorine, or similar chemicals
are used.
●Do not install the boiler in areas where gasoline or
other flammables are used or stored.
●Ensure that combustible materials are stored
away from the boiler and that hanging laundry or
similar items do not obstruct access to the boiler
or its venting.
High Elevation Installations
This unit may be installed at elevations up to 10,100
ft (3,078 m) for use with natural gas and propane.
Refer to“6. Setting the DIP Switches”on page 79
for the appropriate altitude setting.
2.3 Mounting the Boiler to the
Wall
Navien NFC-H boilers come with an upper mounting
bracket that is pre-drilled at 16 in (400 mm) on
center for easy installation on standard wall studs.
If the strength of the wall is insufficient or if the
framing is non-standard or uneven, reinforce the
area before installing the boiler. Avoid installation
on common walls as the unit will make some
operational noises while it is running.
To mount the boiler to the wall:
1. Affix the bracket securely to the wall and ensure
that it is level and that it can support the weight
of the boiler.
2. Align the grooves on the back of the boiler with
the tongues on the mounting bracket and hang
the boiler on the bracket.
When mounted with the mounting bracket, the
boiler will have a
5
/
8
in (16 mm) clearance from
the back of the wall.
Adequate Installation Clearances
CAUTION
Do not install the boiler on carpeting.
Install the boiler in an area that allows for service
and maintenance access to utility connections,
piping, filters, and traps. Based on the installation
location, ensure that the following clearances are
maintained:
Top
Back
Side
Bottom
Front
Side
Clearance from: Indoor Installation
Top 9 in (229 mm) minimum
Back 0.5 in (13 mm) minimum
Front 4 in (100 mm) minimum
Sides 3 in (76 mm) minimum
Bottom 12 in (300 mm) minimum
CAUTION
It is necessary to leave clearance for service
access.

19Installing the Boiler
CAUTION
●Ensure that the structure of the installation
location is sturdy enough to support the full
weight of the installed boiler, including the
water contained in the heat exchanger and
related piping.
●The wall must be vertical, and it must be
capable of carrying the weight of the boiler.
●Do not mount the boiler to drywall that has
not been reinforced.
3. Install two set screws through the bracket at the
bottom of the boiler to secure the boiler on the
wall.
WARNING
●The boiler is heavy. Always lift the unit with
assistance. Be careful not to drop the boiler
while lifting or handling it to avoid bodily
injury or damage to the unit.
●Do not rest the boiler on the bottom end
after removing it from the shipping carton.
Doing so may result in excessive pressure on
protruding pipes and resulting in product
damage. If you must put the boiler down, lay
it on its back or put it inside the protective
shipping base.
●Install the boiler in the upright, vertical
position. Installation in any other orientation
will result in improper boiler operation and
property damage, and could result in serious
personal injury or death.

20 Installing the System Piping
Prior to connecting piping to the boiler, flush the
entire system to ensure it is free of sediment, flux,
solder, scale, debris or other impurities that may
be harmful to the system and boiler. During the
assembly of the heating system, it is important
to keep the inside of the piping free of any debris
including construction dust, copper burr, sand and
dirt.
For retrofits, all system piping including radiators,
must be cleaned of all build-up including sludge
and scale. All systems, old and new, must be
cleaned to remove flux, grease and carbon residue.
Navien recommends cleaning the boiler system
with cleaning products specially formulated
for boiler systems. For retrofit applications with
heavy limescale and sludge deposits, a heavier
duty cleaner may be required. For information on
performing the cleaning, follow the instructions
included with the boiler system cleaner products.
WARNING
Failure to rid the heating system of the
contaminants listed above will void your
warranty and may result in premature heat
exchanger failure and property damage.
3.1 Installing a Space Heating
System
The fire-tube type heat exchanger of the Navien
NFC-H boiler is designed to attain the highest level
of heat transfer in a compact design. To accomplish
this, the heated gas flows through a series of small-
diameter tubes, maximizing the heat transfer area.
To maintain the efficient and reliable operation of
the heat exchanger, and to avoid heat exchanger
failure, it is critical to ensure the rules and guidelines
in this section are followed.
WARNING
●To avoid damaging the connectors on the
boiler, use two wrenches when tightening
pipings to the boiler. Use one wrench to
prevent the connector at the boiler from
turning, and use the other wrench to tighten
the connection. Damaged connectors may
result in system leaks.
●Properly support the pipings with hangers.
Do not allow the pipings to be supported by
the boiler or its accessories.
CAUTION
Failure to follow the instructions provided in this
section will void the warranty and may result in
property damage, fire, serious injury or death.
3. Installing the System Piping