Navien NPN User manual

Getting Service
If your water heater requires service, you have several options for getting service:
●Contact Technical Support at 1-800-519-8794 or on the website: www.navieninc.com.
●For warranty service, always contact Technical Support first.
●Contact the technician or professional who installed your water heater.
●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.navieninc.com
20 Goodyear lrvine, CA 92618
Installation & Operation Manual
NPN Non-Condensing Water Heaters
TANKLESS WATER HEATERS · BOILERS
Version: 1.0 (January. 2021)

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.
The installation must conform with local codes or, in the absence of local codes, the National Fuel Gas
Code, ANSI Z223.1/NFPA 54.
When applicable, the installation must conform with the Manufactured Home Construction and
Safety Standard,Title 24 CFR, Part 3280.
Do not install this water heater in a recreational vehicle, trailer, boat or other vehicular type unit as it
will result in a Carbon Monoxide Poisoning Hazard.
Keep this manual near this water heater 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 & Operation Manual
NPN Non-Condensing Water Heaters
Model NPN-160U
NPN-180U
NPN-199U
NPN-120E
NPN-160E
NPN-180E
NPN-199E
* Lead Fr
ee

2Contents
6. Appendixes 55
6.1 Covering the Clamps with Front Cover
Cap 55
6.2 Technical Data 56
6.3 Wiring Diagram 57
6.4 Ladder Diagram 58
6.5 Component Assembly Diagrams and
Parts Lists 59
6.6 Installation Check list 70
6.7 Navien HAir Add-on Controller Kit
(Optional) 72
6.8 Navien HotButton Kit (Optional) 73
6.9 Requirements for the State of
Massachusetts 74
1. Safety Information 3
2. About the Water Heater 6
2.1 Items Included 6
2.2 Accessories 6
2.3 Specifications 7
2.4 The Front Panel 8
2.5 Components 9
2.6 Dimensions 11
2.7 Rating Plate 13
3. Installing the Water Heater 14
3.1 Choosing an Installation Location 14
3.2 Mounting the Water Heater to the Wall 18
3.3 Connecting the Gas Supply 19
3.4 Connecting the Water Supply 25
3.5 Venting the Water Heater (Indoor Models
Only) 31
3.6 Connecting the Power Supply 42
3.7 Setting the DIP Switches 44
4. Configuring the Remote Controller
System 46
4.1 Included Items 46
4.2 Connecting the Extension Cable 46
4.3 Attaching the Wall Mounting Bracket 46
4.4 Remote Controller 47
4.5 Multi Remote Controller System 48
4.6 Entering Lock Mode 50
4.7 Setting the clock 50
4.8 Setting the Recirculation timer 51
4.9 Starting Recirculation 52
4.10 Canceling all timer settings 52
5. Installing a Cascade System 53
5.1 Connecting Water Supplies 53
5.2 Connecting the Communication Cables 54
Contents

3Safety 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
which, 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 use or store flammable products,
such as gasoline, solvents, or adhesives in
the same room or area as the water heater.
●The water heater 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 water heater’s main burner flame by air
current.
●Keep all flammable products far away from
the water heater and store them in approved
containers. Keep the containers closed tightly
and out of the reach of children and pets.
1. Safety Information

4Safety 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 water heater unless the
water and gas supplies are fully opened.
Doing so may damage the water heater.
●Do not turn on the water if the cold water
supply shut-off valve is closed.
Doing so may damage the water heater.
●Do not use this water heater for anything
other than its intended purpose, as
described in this manual.
●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
water heater.
●This water heater has been approved for
use in the USA only.
Using the water heater in any other country
will void the manufacturer’s warranty.
WARNING
●Do not store or use gasoline or other
flammable liquids near this water heater.
Doing so may result in fire or explosion.
●Do not place combustibles, such as
newspapers or laundry, near the water
heater 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 water heater or venting system,
including the vent termination.
Doing so may result in fire or explosion.
●Do not remove the front cover unless the
power to the water heater is turned off or
disconnected.
Failure to do so may result in electric shock.
●Do not operate the water heater 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 water heater 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 water heater with wet
hands.
Doing so may result in electric shock.

5Safety Information
DANGER
This water heater’s 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, using a lower temperature
setting is recommended.
●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.

6About the Water Heater
2.1 Items Included
When you open the box, you will find the following
items with the water heater. Check the box for each
of the following items before installing the water
heater.
Installation & Operation
Manual, User’s
Information Manual
Tapping Screws &
Anchors
Front Cover Caps Remote Controller
(outdoor models only)
2.2 Accessories
The following optional accessories are available for
the water heater:
Remote Controller
(indoor models only)
Plumb Easy Valve Set
with Pressure Relief
Valve
Ready-Link
Communication Cable
Outdoor Vent Kit
(indoor models only)
External Pump
Connector
(<150W,1.5A)
Navien HotButton
Kit / HAir Add-on
Controller Kit
Navi-Link
(Wi-Fi Control System) Ready-Link Rack
Recess Box
(outdoor models only) Pipe Cover
Gas Conversion Kit
2. About the Water Heater

7About the Water Heater
2.3 Specifications
The following table lists the specifications for the water heater. Additional specifications about water, gas,
electric, and air supplies (venting) appear in the Installation section.
Item
Universal Outdoor
NPN-160U-
NG
NPN-160U-
LP
NPN-180U-
NG
NPN-180U-
LP
NPN-199U-
NG
NPN-199U-
LP
NPN-120E-
NG
NPN-120E-
LP
NPN-160E-
NG
NPN-160E-
LP
NPN-180E-
NG
NPN-180E-
LP
NPN-199E-
NG
NPN-199E-
LP
Heat
Capacity
(Input)
Natural Gas 10,700-
160,000
BTU/H
10,700-
180,000
BTU/H
10,700-
199,900
BTU/H
10,700-
120,000
BTU/H
10,700-
160,000
BTU/H
10,700-
180,000
BTU/H
10,700-
199,900
BTU/H
Propane Gas
Uniform
Energy
Factor
UEF
(for NG & LP)
0.81 0.81 0.81 0.81 0.81 0.81 0.81
Flow Rate
(DHW)
45 °F (25 °C)
Temp Rise
5.8 GPM
(22 L/m)
6.6 GPM
(25 L/m)
7.4 GPM
(28 L/m)
4.2 GPM
(15.9 L/m)
5.8 GPM
(22 L/m)
6.6 GPM
(25 L/m)
7.4 GPM
(28 L/m)
67 °F (36 °C)
Temp Rise
4.0 GPM
(15 L/m)
4.5 GPM
(17 L/m)
5.0 GPM
(19 L/m)
2.9 GPM
(11 L/m)
4.0 GPM
(15 L/m)
4.5 GPM
(17 L/m)
5.0 GPM
(19 L/m)
Dimensions 14.0 in (W) x 23.0 in (H) x 9.3 in (D)
Weight (Gross) 55 lbs (25 kg) 60 lbs (27 kg) 60 lbs (27 kg) 55 lbs (25 kg) 55 lbs (25 kg) 60 lbs (27 kg) 60 lbs (27 kg)
Installation Type Indoor Wall-Hung
(Vent Kit Optional for Outdoor) Only Outdoor Wall-Hung
Venting Type Forced Draft Direct Vent (Indoor only)
Ignition Electronic Ignition
Water Pressure 15-150 PSI
Natural Gas Supply
Pressure
(from source)
3.5 in WC-10.5 in WC
Propane Gas Supply
Pressure (from source) 8 in WC-13 in WC
Natural Gas Manifold
Pressure (Max.–Min.)
2.83 in W.C,
0.70 in W.C
2.25 in WC,
0.53 in WC
2.81 in WC,
0.53 in WC
2.99 in W.C,
0.67 in W.C
3.23 in W.C,
0.69 in W.C
2.38 in WC,
0.53 in WC
2.99 in WC,
0.52 in WC
Propane Gas Manifold
Pressure (Max.–Min.)
5.93 in W.C,
1.38 in W.C
5.28 in WC,
1.31 in WC
6.55 in WC,
1.31 in WC
6.65 in W.C,
1.54 in W.C
6.34 in W.C,
1.35 in W.C
5.39 in WC,
1.28 in WC
6.61 in WC,
1.28 in WC
Minimum Flow Rate 0.5 GPM (1.9 L/m)
Connection
Sizes
Cold Water
Inlet 3/4 in NPT
Hot Water
Outlet 3/4 in NPT
Gas Inlet 3/4 in NPT
Power
Supply
Main Supply 120 V AC, 60 Hz
Normal 90 W 88 W 120 W 90 W 90 W 88 W 120 W
Standby 4 W
Anti-frost 114 W
External
Pump < 150 W, 1.5 A
Fuse 5.0 A
Materials
Casing Cold Rolled Carbon Steel
Heat
Exchangers Stainless Steel
Safety Devices Flame Rod, APS, Vent Installation Detector, Ignition Operation Detector,
Water Temperature High Limit Switch, Power Surge Fuse

8About the Water Heater
2.4 The Front Panel
The front panel allows you to adjust the water temperature and view the operating status or error codes. Remove
the protective sheet from the front panel before using it.
Note The front panel of the outdoor model is placed inside the water heater. It is used only for installation
and maintenance.
a
b
c
d
e
f
g
h
i
j
k
af
h
ci
dj
ek
For indoor models For outdoor models
a
Error
g
Master Unit
A code will appear on the display Cascade operation
b
Hot Water Recirculation
h
Display
Recirculation Mode
c
Diagnostics button
i
Up button
For installers only Increases the temperature
d
Information button
j
Down button
Shows basic information Decreases the temperature
e
Reset button
k
Power button
Resets the water heater (When an error occurs) Turns the water heater on or off
f
Combusting
When the gas burner is on

9About the Water Heater
2.5 Components
The following diagram shows the key components of the water heater. Component assembly diagrams and
particular parts lists are included in the Appendixes.
Intake Air/Exhaust Duct
Condensate Drain
STS Heat Exchanger
NaviTech
TM
Burner
Ignitor&Flame Rod
Front Panel
PCB
Water Inlet Filter
Gas Inlet Fitting
Fan Motor
Ignition Transformer
APS (Air Pressure Sensor)
DHW Supply Fitting
Cold Water Inlet Adapter
[NPN-160U/180U/199U]

10 About the Water Heater
STS Heat Exchanger
Ignitor&Flame Rod
NaviTech
TM
Burner
Front Panel
PCB
Water Inlet Filter
Gas Inlet Fitting
Fan Motor
Ignition Transformer
APS (Air Pressure Sensor)
DHW Supply Fitting
Cold Water Inlet Adapter
[NPN-120E/160E/180E/199E]

11About the Water Heater
2.6 Dimensions
The following diagrams show the dimensions of the water heater and the table lists the supply connections.
24.9 in (633 mm) 23 in (583 mm)
Supply Connections
Description Diameter
AExhaust Gas Vent 3 in
BAir Intake 5 in
CHot Water Outlet
3
/
4
in
DCold Water Inlet
3
/
4
in
EGas Inlet
3
/
4
in
FCondensate Drain
5
/
8
in
Overhead View
A B
F
3.7 in (93 mm)
7 in (178 mm)7 in (178 mm)
0.4 in
(11.2 mm)
Supply Connections
C ED
9.3 in (236.2 mm)
4.2 in (105.7 mm)
2.7 in
(68 mm) 3.2 in (80.1 mm) 4.9 in (124.1 mm)
14 in (356 mm)
1.8 in (45.8 mm)
4.8 in (122 mm)
[NPN-160U/180U/199U]

12 About the Water Heater
24.9 in (633 mm)
7.9 in (201.6 mm)
1 in (26 mm)
23 in (583 mm)
Supply Connections
Description Diameter
AHot Water Outlet
3
/
4
in
BCold Water Inlet
3
/
4
in
CGas Inlet
3
/
4
in
Overhead View
9.4 in (239.1mm)
0.4 in (11.2 mm)
Supply Connections
A CB
4.2 in (105.7 mm)
14 in (356 mm)
2.7 in
(68 mm) 3.2 in (80.1 mm) 4.9 in (124.1 mm)
1.8 in (45.8 mm)
4.8 in (122 mm)
[NPN-120E/160E/180E/199E]

13About the Water Heater
2.7 Rating Plate
Water Heaters come from the factory configured for use with Natural Gas (NG) or Propane Gas(LP). Before
starting the installation, check the rating plate located on the side of the water heater to ensure that the water
heater matches the gas type, gas pressure, water pressure, and electrical supply available in the installation
location. If the water heater does not match each of these ratings, do not install the water heater. If
conversion to Propane Gas or Natural Gas is required, the Gas conversion kit (optional) must be used.
WARNING
●Be sure the gas type and electricity voltage match the rating plate. Using a different gas type will cause
abnormal combustion, excessive carbon monoxide emissions and water heater malfunction.
●Using abnormally high or low AC voltage may cause abnormal operation, and may reduce the life
expectancy of this product.

14 Installing the Water Heater
3.1 Choosing an Installation
Location
When choosing an installation location, you must
ensure that the location provides adequate clearance
for the water heater, adequate venting and drainage
options, and sufficient access to gas, water, and
electrical supplies. Carefully consider the following
factors when choosing an installation location:
CAUTION
Review the entire installation information in this
manual before starting installation. Consider all
the requirements for venting, piping, and wiring.
WARNING
Do not install this water heater in a recreational
vehicle, trailer, boat or other vehicular type unit
as it will result in a Carbon Monoxide Poisoning
Hazard.
About Water Quality
Proper maintenance of the water heater is required
when water quality does not meet EPA standards.
Damage caused by poor water quality is not
covered under warranty. The following table shows
the maximum contaminant levels allowed, based
on the EPA National Secondary Drinking Water
Regulations (40 CFR Part 143.3). If you suspect that
your water is contaminated in any way, discontinue
use of the water heater and contact an authorized
technician or licensed professional.
Contaminant Maximum Allowable Level
Total Hardness Up to 200 mg/l (12 grains/gallon)
Aluminum 0.05 to 0.2 mg/l
Chloride Up to 250 mg/l
Copper Up to 1.0 mg/l
Iron Up to 0.3 mg/l
Manganese Up to 0.05 mg/l
pH 6.5 to 8.5
Sulfate Up to 250 mg/l
Total Dissolved
Solids (TDS) Up to 500 mg/l
Zinc Up to 5 mg/l
Chlorine Up to 4 mg/l
If your local water is hard, please review the
following recommended treatment and flushing
guidelines.
Hardness Level Treatment
Method
Flush
Frequency*
Soft 0-4 grains/gal
(0-60 mg/L) None None
Moderately
Hard
4-7 grains/gal
(61-120 mg/L)
Water Softener**
or Navien
PeakFlow is
Recommended
Once/Year
Hard 7-9 grains/gal
(121-160 mg/L)
Residential:
Once/Year
Very Hard 9-12 grains/gal
(161-200 mg/L)
Water Softener**
or Navien
PeakFlow
is HIGHLY
Recommended
Extremely
Hard
>12 grains/gal
(200 mg/L)
Water Softener**
or Navien
PeakFlow is
Required
* Flushing is recommended if a treatment device is
not installed. This procedure should be performed
using white vinegar or solutions that are specifically
formulated for use on tankless water heaters. See Water
Heater Flush Procedures.
**Check local codes for any restrictions on use of water
softeners
Water Heater Flushing Procedures
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“Dimensions” on page 11 for 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
3. Installing the Water Heater

15Installing the Water Heater
10. Rinse the cleaning solution from the water
heater:
a. Remove the free end of the drain tube from
the bucket and place it in the condensate
drain or laundry tub (wherever the water
heater drains).
b. Close the“B”valve and open the “D” valve. Do
not open the “C” valve yet.
c. Allow water to flow through the water heater
for 5minutes.
d. Close the“A”valve and open the “C” valve.
11. Disconnect all tubes.
12. Remove the cold water inlet filter from the water
heater and clean out any residue.
13. Reinsert the filter and ensure the filter cap is
securely tightened.
14. Reconnect the power supply to the Water
Heater.
15. Press the Power button on the front panel to
turn on the water heater.
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.
To flush the Heat Exchanger:
A
A
B
B
C
C
D
D
Navien Easy
Valve Kit
Cold Water Line
Hot Water Line
Circulation Pump
Flushing Kit
1. Press the Power button on the front panel to
turn off the water heater.
2. Disconnect the power supply to the water
heater.
3. Close the “C” and “D” valves on the hot and cold
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 cold water line at the“B”
valve.
6. Connect one tube to the circulation pump inlet
and place the free end in the bucket.
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 water heater
for at least 45minutes.

16 Installing the Water Heater
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 “3.5 Venting the Water Heater (Indoor Models
Only)” on page31.
WARNING
Improper venting of the water heater can result
in excessive levels of carbon monoxide, which
can lead to severe personal injury or death. This
water heater must be vented in accordance
with the “Venting of Equipment“ section of
the latest edition of the ANSI Z223.1/NFPA
54 Natural Fuel Gas Code in the USA, as
well as all applicable local building codes
and regulations. Follow all instructions and
guidelines when venting the water heater.
Venting should be performed only by a qualified
service agency.
To ensure adequate venting and ventilation, follow
these guidelines:
●Maintain proper clearances from any openings in
the building.
●Install the water heater with a minimum clearance
of 12 in
(300 mm) above an exterior grade or as required
by local codes.
●Maintain a minimum clearance of 4 ft (1.2 m) from
heating and cooling vents.
●Do not enclose the vent termination.
●Install the exhaust vent in an area that is free from
obstructions and does not allow the exhaust to
accumulate.
●Do not install the water heater where moisture
from the exhaust may discolor or damage walls.
●Do not install the water heater in bathrooms,
bedrooms, or any other occupied rooms that are
normally kept closed or that are not adequately
ventilated.
●Install a carbon monoxide detector in the
dwelling area that is closest to the appliance.
Adequate Drainage
This non-condensing water heater may produce
condensate due to the condition of the installation.
Condensate can be drained through the condensate
collector. The water heater should be located near
a suitable drain and where damage from a possible
leak will be minimal. Installing the water heater in a
location without a drain will void the warranty and
Navien will not be responsible for water damages
that occur as a result.
The water heater 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 water heater is
highly recommended. When installing the drain
pan, ensure that the installation does not restrict
combustion air flow.

17Installing the Water Heater
For outdoor installation
Clearance
from: to Combustibles to Non-
Combustibles
Top 12 in (305 mm)
minimum
2 in (51 mm)
minimum
Back 0 in (0 mm)
minimum
0 in (0 mm)
minimum
Front
(panel)
24 in (610 mm)
minimum
0 in (0 mm)
minimum
Front
(exhaust)
24 in (610 mm)
minimum
24 in (610 mm)
minimum
Sides 6 in (152 mm)
minimum
1/8 in (3.2 mm)
minimum
Ground/
Bottom
12 in (305 mm)
minimum
2 in (51 mm)
minimum
Clean, debris and chemical-free
combustion air
●Do not install the water heater in areas where
dust and debris may accumulate or where hair
sprays, spray detergents, chlorine, or similar
chemicals are used.
●Do not install the water heater in areas where
gasoline or other flammables are used or stored.
●Ensure that combustible materials are stored
away from the water heater and that hanging
laundry or similar items do not obstruct access to
the water heater or its venting.
Note The combustion air must be free
of flammable vapors or corrosive
chemical fumes. Common
corrosive chemical fumes to
avoid include fluorocarbons and
other halogenated compounds
such as Freon, trichloroethylene,
perchlorethylene, chlorine, which
can be found in refrigerants or
solvents. When these chemicals
burn, they produce acids that
corrode the stainless steel heat
exchanger, gaskets, and the flue
and vent system.
●In commercial locations, do not install the water
heater in areas with greasy fumes or heavy
amounts of steam or take measures to prevent
fumes and steam from entering the water heater.
Proximity to fixtures and appliances
Install the water heater 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 water
heater requires “instant“ hot water, we recommend
running a recirculation line back to the water heater
from the furthest fixture. Insulate as much of the hot
water supply and recirculation lines as possible. For
more information about the water supply, refer to
“3.4 Connecting the Water Supply“ on page 25.
Adequate installation clearances
Install the water heater in an area that allows
for service and maintenance access to utility
connections, piping, filters, and traps. Based on the
installation location, ensure the following clearances
are maintained:
For indoor installation
Clearance
from: to Combustibles to Non-
Combustibles
Top 6 in (152 mm)
minimum
2 in (51 mm)
minimum
Back 0 in (0 mm)
minimum
0 in (0 mm)
minimum
Front 6 in (152 mm)
minimum
6 in (152 mm)
minimum
Sides 2 in (51 mm)
minimum
1/2 in (13 mm)
minimum
Ground/
Bottom
12 in (305 mm)
minimum
12 in (305 mm)
minimum
Vent 0 in (0 mm)
minimum
0 in (0 mm)
minimum

18 Installing the Water Heater
3.2 Mounting the Water Heater to
the Wall
Navien water heaters come with two upper and
lower mounting brackets that are pre-drilled at 16
in 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 water heater. Avoid installation
on common walls as the unit will make some
operational noises while it is running.
WARNING
●If the water heater is not properly and
securely attached to the wall, it could become
dislodged causing the exhaust vent pipe to
separate. This can result in carbon monoxide
emissions which could cause severe personal
injury or death.
●Be careful not to drop the water heater while
lifting or handling it to avoid bodily injury or
damage to the unit.
●Do not rest the water heater on the bottom
end after removing it from the shipping
carton. Doing so may result in excessive
pressure on protruding pipes and cause
product damage. If you must put the water
heater down, lay it on its back or put it inside
the protective shipping base.
●Install the water heater upright in the vertical
position. Installation in any other orientation
will result in improper water heater operation
and property damage, and could result in
serious personal injury or death.
CAUTION
●Ensure that the structure of the installation
location is sturdy enough to support the full
installed weight of the water heater, including
water content of the heat exchanger and
related piping.
●The wall must be vertical, and it must be
capable of carrying the weight of the water
heater.
●Do not mount the water heater to dry wall
that has not been reinforced.
High Elevation Installations
This water heater may be installed at elevations up
to 10,100 ft (3,078 m) for use with Natural Gas and
Propane. Refer to“3.7.2 Setting the Front Panel DIP
Switches” on page44 for the appropriate altitude
setting.
Coastal Installations
For installations in sea or marine environments, the
salty air can cause corrosion to the water heater. The
water should be protected and enclosed to minimize
exposure to the corrosive atmosphere. Damage due
to a corrosive environment is not covered under
warranty.
Operating Temperature
The ambient temperature at the installation location
must be above freezing temperature and below
120˚F (49˚C).

19Installing the Water Heater
3.3 Connecting the Gas Supply
WARNING
●Before connecting the gas supply, determine
the gas type and pressure for the water heater
by referring to the rating plate. Use only
the same gas type indicated on the rating
plate. Using a different gas type will result
in abnormal combustion and malfunction
of the water heater. Gas supplies should be
connected by a licensed professional only.
●To avoid damaging the connectors on
the water heater, use two wrenches when
tightening pipings to the water heater. Use
one wrench to prevent the connector at the
water heater 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 water heater or its accessories.
●Ensure that the gas piping is protected
from physical damage and freezing, where
required. Failure to follow these instructions
could result in gas leakage, and result in fire,
explosion, property damage, severe personal
injury, or death.
●The appliance and its gas connection must
be leak tested before placing the appliance
in operation.
●To avoid danger of explosion and fire, do not
use flame to check for a gas leak. Perform a
bubble test on the joints to check for gas
leaks. If a leak exists, bubbles will form at
the leaking joint. A gas leak could result
in substantial property damage, severe
personal injury, or death.
●This water heater cannot be converted from
natural gas to propane or vice versa without
a Navien gas conversion kit. Do not attempt a
field conversion of this water heater without
a Navien gas conversion kit installed by a
qualified service agency.
To mount the water heater to the wall:
1. Ensure that the strength of the wall is sufficient
to support the weight of the water heater.
2. Securely attach the water heater to the wall by
affixing the brackets at the top and bottom of
the water heater.
3. Ensure that the water heater is level using a
leveling tool.
4. The top and bottom mounting brackets are
adjustable to provide flexibility in aligning the
vent with the vent collar on the water heater.