Navien NHW700 Guide

Getting Service
If your water heater requires service:
●All repairs require pre-authorization by Technical Support.
●Request for your installer or any licensed professional to contact Technical Support at
1-800-519-8794 Option 2 once at the installation site.
●A short list of independent service providers in your area can be found on the website:
www.navieninc.com/installers.
●Contact a licensed professional for the affected system (for example, a plumber, gas fitter,
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
User’s Information Manual
NHW700 Non-Condensing Water Heaters
TANKLESS WATER HEATERS · BOILERS
Version: 1.0 (August, 2023)

User’s Information Manual
NHW700 Non-Condensing Water Heaters
Model
NHW700-160AI/180AI/199AI
NHW700-160AE/180AE/199AE
* Lead Fr
ee
ALWAYS read and follow this manual completely before using
the water heater. Save for future reference.
Tested and Certified to NSF/ANSI 372 for lead free* compliance.
* The wetted surface of this product contacted by consumable
water contains less than one quarter of one percent (0.25%) of
lead by weight.
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 moving vehicles as it will
result in a Carbon Monoxide Poisoning Hazard.

2Contents
Contents
1. Important Safety Information 3
2. About the Water Heater 7
2.1 Description of the Water Heater 7
2.2 Parts of the Water Heater 7
2.3 The Front Panel (Indoor Models Only) 8
2.4 Remote Controller (Outdoor Models -
Optional for Indoor Models) 9
3. Operating the Water Heater 10
3.1 Turning the Water Heater On or Off 10
3.2 Adjusting the Water Temperature 11
3.3 Viewing Basic Information (Indoor
Models Only) 12
3.4 Resetting the Water Heater 12
3.5 Entering Lock Mode 13
3.6 Setting the Clock 13
3.7 Setting the Recirculation Timer 14
3.8 Starting Recirculation 15
3.9 Canceling Timer Settings 15
4. Maintaining the Water Heater 16
4.1 Cleaning the Water Heater 16
4.2 Draining the Water Heater 16
4.3 Flushing the Heat Exchanger 18
4.4 Cleaning the Inlet Water Filter 20
4.5 Protecting the Water Heater from Freezing 20
5. Troubleshooting 22
5.1 Solving Basic Problems 22
6. LIMITED WARRANTY NAVIEN, INC. 23
Product Installation Information
Model
Date Purchased
Gas Type
Serial Number

3Important Safety Information
The following Safety Alert Symbols are used in this
manual. They are used to alert you to potential
personal injury hazards. Obey all safety messages
that follow this symbol to avoid possible serious
injury or death. These Safety Alert Symbols precede
any safety message about risk of personal injury. It
may also be accompanied by one of the following
signal words.
If the information in these instructions is not
followed exactly, a fire or explosion may result,
causing property damage, personal injury or death.
DANGER
Indicates a hazardous situation that if not
avoided will result in death or serious injury.
WARNING
Indicates a hazardous situation that if not
avoided could result in death or serious injury.
CAUTION
Indicates a potentially hazardous situation that
if not avoided could result in minor or moderate
injury.
NOTICE
Indicates information considered important but
not hazard-related (such as property damage).
WARNING
To prevent death, serious injury, or property
damage:
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 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 supplier, call
the fire department.
C. Use only your hand to push in or turn the
gas control knob. Never use tools. If the
knob will not push in or turn by hand,
don’t try to repair it, call a qualified service
technician. Force or attempted repair may
result in a fire or explosion.
D. 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.
1. Important Safety Information

4Important Safety Information
DANGER
HOT
BURN
Water temperature over 125°F (52°C) can cause
severe burns instantly or death from scalds.
Children, disabled and elderly are at highest risk
of being scalded. Feel water with your elbow
before bathing or showering. Temperature
limiting valves are available, contact a licensed
plumber for more information.
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.
●Check local codes for maximum water
temperature setting allowed when used in
nursing homes, schools, day care centers and
other public applications.
●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.
DANGER
This water heater 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 table
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
Before setting the temperature at or 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.
SAVE THESE
INSTRUCTIONS
DANGER
Indicates a hazardous
situation that if not
avoided will result in
severe injury or death.
WARNING
Indicates a hazardous
situation that if not
avoided could result
in death or serious
injury.
CAUTION
Indicates a potentially
hazardous situation
that if not avoided
could result in minor
or moderate injury.
NOTICE
Indicates information
considered important
but not hazard-
related (such as
property damage).

5Important Safety Information
WARNING
To prevent death, serious injury, or property
damage:
●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. Inspect
the vent termination and air intake supply
annually to ensure proper operation of the
water heater. Turn off and discontinue use of
the water heater 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 water heater with wet
hands.
Doing so may result in electric shock.
California law requires the following Prop 65
warning to be provided:
WARNING
Cancer and Reproductive Harm -
www.P65Warnings.ca.gov
WARNING
To prevent death, serious injury, or property
damage:
●Shut off the gas supply if the water heater
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 water heater is damaged as a result of
overheating, fire, flood, or any other reason,
close the manual shut off valve and do not
operate the water heater again until it has
been inspected by a qualified technician.
●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.

6Important Safety Information
CAUTION
●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.
●Should overheating occur or the gas supply
fail to shut off, turn off the manual gas valve
to the appliance.
●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.
CAUTION
●Do not attempt to repair or replace any part
of the water heater, 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 water heater 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 water heater.
Doing so may result in product damage or
personal injury.
●Do not attempt to change the water
temperature while the water heater is being
used.
Doing so may result in personal injury.
●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.

7About the Water Heater
2.1 Description of the Water
Heater
The NHW700-A series water heater is available in
6 models:
NHW700-160AE, NHW700-180AE, NHW700-199AE,
NHW700-160AI, NHW700-180AI and NHW700-
199AI.
●I (Interior): For INDOOR use ONLY
●E (Exterior): For OUTDOOR use ONLY
●A (Advanced): Built-in Pump and 0.4 US Gallon
(1.5 liter) Buffer Tank for internal or external
recirculation
The main features are as follows:
●Potable domestic hot water and combination
space heating
●Maximum temperature: 140°F (60°C)
●Stainless steel heat exchanger with stainless steel
piping
2.2 Parts of the Water Heater
2.2.1 Front View
Air IntakeAir Intake
Exhaust Gas
[NHW700-AI Models]
Air Intake Air Intake
Exhaust Gas
[NHW700-AE Models]
2.2.2 Bottom View
d
e
f
a
c
b
#Description Remark
aPump Drain Port
bHot Water Outlet Connection
cRecirculation Inlet
dGas Inlet
eInlet Water Filter
fCold Water Inlet Connection
2. About the Water Heater

8About the Water Heater
2.3 The Front Panel (Indoor Models Only)
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.
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
Combustion
When the gas burner is on
a
b
c
d
e
f
g
h
i
j
k

9About the Water Heater
2.4 Remote Controller (Outdoor Models - Optional for Indoor Models)
LCD display
Indicates functions and
current status.
LEDindicator
Indicates the status of water
heater.
- Green: Normal Mode.
- Red: Erroroccurred.
Preheat & Timer button
- Access the timer settings.
- Recirculation ON.
Up button
Increase the temperature
or value.
Down button
Decrease the temperature
or value.
Lock button
Locks the other button
operations.
Power button
Turns the remote controller
OK button
on or off.
LCD display
Indicates functions and
current status.
LED indicator
Indicates the status of
water heater.
- Green: Normal Mode.
- Red: Error occurred.
OK button
Confirms the selection.
Power button
Turns the remote
controller on or off.
Lock button
Locks the other button
operations.
Down button
Decrease the temperature
or value.
Up button
Increase the temperature
or value.
Preheat & Timer button
- Access the timer settings.
- Recirculation ON.
Timer is set. Recirculation Mode.
Displays the current time. Hot water is in use.
Displays the current set
temperature. Water heater operation is in progress.
Operations are locked. An error code will appear on the
display.

10 Operating the Water Heater
WARNING
To prevent death, serious injury or property
damage:
●Ensure that the water heater is filled with
water before turning on the water heater.
●If overheating occurs or the gas supply fails to
shut off, shut off the gas supply to the water
heater at the manual gas valve.
●If any part of the water heater has been
submerged in water, do not use this
appliance and immediately call a qualified
service technician. The water heater must be
replaced.
3.1 Turning the Water Heater On
or Off
To turn the water heater on or off, press the Power
button.
[Indoor Models]
[Outdoor Models with Remote Controller]
When the power is on, the temperature will appear
on the front panel display.
[Indoor Models] [Outdoor Models with
Remote Controller]
3. Operating the Water Heater

11Operating the Water Heater
or
[Outdoor Models with Remote Controller]
Note The water heater will retain your
settings during a power outage.
You can adjust the temperature by the increments
as shown below based on the desired temperature
range.
Temperature range Adjusting the water
temperature
98 °F-140 °F
(Fahrenheit mode)
36 °C-60 °C
(Celsius mode)
1 °F or 0.5 °C
increments
The water heater will not provide hot water instantly
at the hot water faucet unless a recirculation line has
been installed from the furthest fixture back to the
water heater.
3.2 Adjusting the Water
Temperature
WARNING
Before adjusting the water temperature, read
“To prevent burns:” on page 4 carefully.
Water temperatures above 120 °F can cause
instant scalding, severe burns, or death.
The water heater is set to 120 °F (49 °C) by default.
To adjust the water temperature:
1. Make sure that all hot water faucets are closed,
and ensure that the internal circulator and any
external circulating pumps are off.
Note If a hot water faucet is open, you
can adjust the temperature only
from 98-110 °F (37-43 °C).
2. Press the + (Up) or – (Down) buttons until the
desired temperature appears on the display. You
can adjust the temperature while the display
is flashing. Once the display stops flashing, the
temperature setting is stored.
[Indoor Models]

12 Operating the Water Heater
3.4 Resetting the Water Heater
If an error message appears, you can try resetting
the water heater to resolve the problem. To reset the
water heater, press the Reset button.
For outdoor installation models, press the OK button
once and “RST”will be displayed on the LCD display.
If resetting the water heater does not solve the
problem, refer to the Troubleshooting section of this
manual or contact Technical Support at 1-800-519-
8794.
3.3 Viewing Basic Information
(Indoor Models Only)
To view information about the water heater, press
the Information button.
Press the + or – buttons to switch between the
information types.
Display Description
Flow rate in gallons per
minute (GPM).
Hot water outlet temperature
(OUT).
Cold water inlet temperature
(IN).
To exit information mode, press the Reset button.

13Operating the Water Heater
3.6 Setting the Clock
1. Press the Preheat & Timer button for 2 seconds.
2sec
2. Adjust the minutes by pressing the Up or Down
Button.
Press the OK button to set the minutes.
or
3. Once the minutes are set, adjust the hour by
pressing the Up or Down button.
3.5 Entering Lock Mode
To prevent accidental pressing of the buttons and to
prevent children from adjusting the controller, you
can activate the Temperature Lock Mode.
To activate or deactivate Lock Mode, press the Lock
button for 2 seconds.
2sec
When Lock Mode is activated,
●The Lock icon appears on the display.
●All buttons except for Lock button are locked.
Note ●Resetting errors or alarms is still
available with Lock Mode activated.
●You can change the settings from
the front panel with Lock Mode
activated.

14 Operating the Water Heater
2. Set the recirculation activation time by pressing
the Up or Down button.
or
Then, press the OK button to set the
deactivation time.
Note The recirculation timer settings are
divided in 30 minute increments.
3. Set the deactivation time by pressing the Up or
Down button.
or
4. Press the OK button to finish and save the
updated time.
3.7 Setting the Recirculation
Timer
1. Press the Preheat & Timer button to set the
Recirculation timer while setting the clock.
Reservation Schedule #1 is ready to be set.
Note This feature is available only when
external circulating pumps are
connected and ON.

15Operating the Water Heater
3.8 Starting Recirculation
Press the Preheat & Timer button to start
recirculation immediately, regardless of the
reservation schedule.
“HEAT”appears for 4 seconds on the display and
then recirculation runs once.
During the recirculation, the preheating icon flashes
continuously.
Note This feature runs during the
recirculation time set on the front
panel which the remote controller is
connected to.
3.9 Canceling Timer Settings
Press and hold the Preheat & Timer and OK button
simultaneously for 2 seconds.
“CLR”appears for 3 seconds and all timer settings
are canceled.
2sec
4. Press the OK button to save the timer setting.
Repeat these procedures for Reservation
Schedule Settings #2 and #3.
5. During the reservation schedule, the preheating
icon turns on and the Reservation area starts
flashing.

16 Maintaining the Water Heater
4.1 Cleaning the Water Heater
WARNING
Make sure the water heater is turned off and the
power supply is disconnected before cleaning
the water heater. The water heater may remain
hot for several minutes after it is turned off. To
prevent burns, wait until the water heater has
cooled down before cleaning.
To clean the water heater, 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 Water Heater
You need to drain the water heater before
performing maintenance tasks, such as cleaning the
inlet water filter, or to prevent the water heater from
freezing when it will not be used for an extended
period.
Refer to the“2.2 Parts of the Water Heater” on page
7 for details about part locations.
To drain the water heater:
1. Place a bucket under the water heater, to collect
the residual water inside the water heater.
2. Press the Power button on the front panel to
turn off the power to the water heater.
[Indoor Models]
[Outdoor Models with Remote Controller]
3. Close the gas shut-off valve.
OPEN
CLOSE
OPEN
CLOSE
OPEN
CLOSE
Opened
Gas
Shut-Off
Valve
Closed
4. Maintaining the Water Heater

17Maintaining the Water Heater
7. Open the pump drain plug.
8. Remove the cold water inlet filter.
9. Allow the residual water to drain from the water
heater.
10. When the water is completely drained, reinsert
the cold water inlet filter, and then close the
water drain plug.
11. To refill the water heater follow the steps of
“Draining the Water Heater” in reverse.
4. Close the water supply valve on the inlet to the
water heater. If there is no valve, turn off the
water supply at the water main.
5. Open all hot water faucets completely. The
water that remains in the plumbing lines will
drain out.
6. Remove the recirculation inlet filter from the
bottom of the water heater.
Recirculation
Inlet Filter
Pump Drain Plug
Cold Water Inlet
Filter

18 Maintaining the Water Heater
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
page 18 for more information on flushing the heat
exchanger.
**Check local codes for any restrictions on use of water
softeners.
Refer to the“2.2 Parts of the Water Heater” on page
7 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
4.3 Flushing the Heat Exchanger
NOTICE
Flushing the Heat Exchanger can be a difficult
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.
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

19Maintaining 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.
To flush the Heat Exchanger:
A
A
B
B
C
C
D
D
Navien Plumb
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.