Rinnai Demand Duo 80 User manual

Demand Duo™ 80
Installaon and Operaon Manual
—Do not store or use gasoline or other ammable 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 instrucons.
• If you cannot reach your gas supplier, call the re department.
—Installaon and service must be performed by a qualied installer, service agency or the gas supplier.
READ ALL OF THE INSTRUCTIONS THOROUGHLY BEFORE INSTALLING OR
OPERATING THIS SYSTEM.
(This manual is a supplement to the RL94i Installaon and Operaon
Manual)
This manual provides informaon on the installaon, operaon, and maintenance of
the water heater. For proper operaon and safety, it is important to follow the
instrucons and adhere to the safety precauons.
A licensed professional must install the water heater according to the exact
instrucons in this manual.
The consumer must read the enre manual to properly operate the water heater and
to have regular maintenance performed.
The Commercial Hybrid System is assembled with mulple and separately cered
components consisng of:
• RL94i / RLX94i Tankless Water Heater
• 80 Gallon Storage Tank
• Controller
WARNING
IF THE INFORMATION IN THESE INSTRUCTIONS IS NOT FOLLOWED EXACTLY, A FIRE OR EXPLOSION MAY
RESULT CAUSING PROPERTY DAMAGE, PERSONAL INJURY OR DEATH.
Commercial Applicaons:
CHS19980HEiP . .......... 80 Gallon, 199,000 BTU
CHS19980HEiN ........... 80 Gallon, 199,000 BTU
CHS19980HEXiN ......... 80 Gallon, 192,000 BTU
Residenal Applicaons:
RHS19980HEiP . .......... 80 Gallon, 199,000 BTU
RHS19980HEiN ........... 80 Gallon, 199,000 BTU
RHS19980HEXiN ......... 80 Gallon, 192,000 BTU
For Indoor Applicaons Only:

2Demand Duo™ 80
Safety Behaviors and Pracces for the
Consumer and Installer………………………………….……...3
Installaon Instrucons………………………………………...4
Installer Qualicaons…………………………………....4
Type of Installaon………………………………………....4
Installaon Steps………………………………………..……4
General Instrucons………………………………..……….4
Prepare for Installaon………..………….………..…….5
Installaon of Gas Supply……………………..………...8
Connect Electricity………………………………….…….….9
System Controller…………………………………….…. ..10
Installaon of Plumbing………………………….……..11
Typical Installaons………………………….…………...12
This is the safety alert symbol. This symbol alerts you to potenal
hazards that can kill or hurt you and others.
Indicates an imminently hazardous situaon which, if not avoided, will result in personal
injury or death.
Indicates a potenally hazardous situaon which, if not avoided, could result in personal
injury or death.
Indicates a potenally hazardous situaon which, if not avoided, could result in minor or
moderate injury. It may also be used to alert against unsafe pracces.
DAN-
CAUTION
WARNING
Important Safety Informaon
Safety Denions
Piping Diagram for Basic Installaons……………….… 13
Piping Diagram for Mul-Unit Installaons……….….14
Direct Vent Terminal Clearances………………….……....16
Venng Guidelines………………………………………......….17
Condensate………………………………………………........…..19
Final Checklist……………………………………….…...…….....20
Technical Data…………………………………………...…………...…21
Specicaons………………………………………………..……...21
Dimensions…………………………………………………..……...23
Storage Tank Maintenance………………………..…….…..24
Replacement Parts…………………………………..……...…..25
Service/Maintenance Log…….…………..……………….....26
Warranty…………………………………………..………….….....28
TABLE OF CONTENTS

Demand Duo™ 80 3
Safety Behaviors and Pracces for the Consumer and Installer
CAUTION
• BURN HAZARD. Hot exhaust and vent may cause
serious burns. Keep away from the water heater
unit. Keep small children and animals away from
the unit.
• Hot water outlet pipes leaving the unit can be hot
to touch.
• Before operang, smell all around the appliance
area for gas. Be sure to smell next to the oor
because some gas is heavier than air and will sele
on the oor.
• Keep the area around the appliance clear and free
from combusble materials, gasoline, and other
ammable vapors and liquids.
• Combusble construcon refers to adjacent walls
and ceiling and should not be confused with
combusble or ammable products and materials.
Combusble and/or ammable products and
materials should never be stored in the vicinity of
this or any gas appliance.
• Always check the water temperature before
entering a shower or bath.
• To protect yourself from harm, before performing
maintenance:
 Turn o the electrical power supply by
unplugging the power cord or by turning o the
electricity at the circuit breaker. (The
temperature controller does not control the
electrical power.)
 Turn o the gas at the manual gas valve,
usually located immediately below the water
heater.
 Turn o the incoming water supply. This can
be done at the isolaon valve immediately
below the water heater or by turning o the
water supply to the building.
WARNING
• 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, do not try to repair it; call a
licensed professional. Force or aempted repair
may result in a re or explosion.
• Do not use this appliance if any part has been under
water. Immediately call a licensed professional to
inspect the appliance and to replace any part of the
control system and any gas control which has been
under water.
• Do not use substute materials. Use only parts
cered for the appliance.
• Should overheang occur or the gas supply fail to
shut o, turn o the manual gas control valve to
the appliance.
• Do not adjust the DIP switch unless specically
instructed to do so.
• Do not use an extension cord or an adapter plug
with this appliance.
• Any alteraon to the appliance or its controls can
be dangerous and will void the warranty.
• Proper venng is required for the safe operaon of
this appliance.
California law requires this noce to be provided:
California Proposion 65:
This product contains chemicals known to the state of
California to cause cancer, birth defects, or other
reproducve harm.
WARNING

4 Demand Duo™ 80
A licensed professional must install the appliance,
inspect it, and leak test it before use. The warranty
will be voided due to any improper installaon.
The installer should have skills such as:
• Gas sizing.
• Connecng gas lines, water lines, valves, and
electricity.
• Knowledge of applicable naonal, state, and
local codes.
• Installing venng through a wall or roof.
• Training in installaon of Rinnai water heaters.
(Training can be accessed on-line at
www.trainingevents.rinnai.us)
Installaon Steps
Prepare for Installaon ......................................5
Determine Installaon Locaon.........................6
Venng Guidelines.............................................9
Installaon of Plumbing...................................11
Checklist for Plumbing .....................................14
Installaon of Gas Supply.................................15
Connect Electricity ...........................................16
Checklist for Gas and Electricity.......................17
System Controller.............................................17
Condensate ......................................................18
Final Checklist...................................................20
General Instrucons
Installer Qualicaons
DO NOT
• Do not install the Commercial Hybrid System
outdoors.
• Do not install the appliance in an area where water
leakage of the unit or connecons will result in
damage to the area adjacent to the appliance or to
lower oors of the structure. When such locaons
cannot be avoided, it is recommended that a
suitable drain pan, adequately drained, be installed
under the appliance. The pan must not restrict
combuson air ow.
• Do not obstruct the ow of combuson and
venlaon air. Combuson air shall not be
supplied from occupied spaces.
• Do not use this appliance in an applicaon such as
a pool or spa heater that uses chemically treated
water . (This appliance is suitable for lling large or
whirlpool spa tubs with potable water.)
• Do not use substute parts that are not authorized
for this appliance.
MUST DO
• The installaon must conform with local codes or,
in the absence of local codes, with the Naonal
Fuel Gas Code, ANSI Z223.1/NFPA 54, or the
Natural Gas and Propane Installaon Code, CSA
B149.1.
• The appliance, when installed, must be electrically
grounded in accordance with local codes or, in the
absence of local codes, with the Naonal Electrical
Code, ANSI/NFPA 70, or the Canadian Electrical
Code, CSA C22.1.
• The appliance and its appliance main gas valve
must be disconnected from the gas supply piping
system during any pressure tesng of that system
at test pressures in excess of 1/2 psi (3.5 kPa)
(13.84 in W.C.).
• The appliance must be isolated from the gas supply
piping system by closing its individual manual
shuto valve during any pressure tesng of the gas
supply piping system at test pressures equal to or
less than 1/2 psi (3.5 kPa) (13.84 in W.C.).
• You must follow the installaon instrucons and
those in Care and Maintenance for adequate
combuson air intake and exhaust.
Type of Installaon
• For installaon in commercial applicaons only.
INSTALLATION INSTRUCTIONS
(for the licensed professional)

Demand Duo™ 80 5
Prepare for Installaon
Parts included:
Tools needed:
Materials needed:
• Commercial Hybrid System
• Temperature and Pressure Relief Valve (Tank)
• Pressure Relief Valve (Pre-installed on Tankless)
• Pipe wrenches (2)
• Adjustable pliers
• Screwdrivers (2)
• Wire cuers
• Gloves
• Safety glasses
• Level
Tools that might be needed:
• Hammer drill with
concrete bits
• Saw
• Threading machine with
heads and oiler
• Core drill with diamond
head
• Torch set
• Copper tubing cuer
• Steel pipe cuer
Materials that may be needed:
• Soap or gas leak
detector soluon
• Approved venng
• Teon tape
(recommended) or pipe
compound
• Pipe insulaon
• Heat tape
• Electrical wire and
conduit per local code
• PVC glue/cement
• 5/8” ID PVC exible
tubing
• 2 conductor 22 AWG
wire for controller
• Single gang electrical
box
• Wire nuts
• Unions and drain valves
• Drain Pan
• Earthquake Strap
General Instrucons (Connued)
INFORMATION
• If a water heater is installed in a closed water
supply system, such as one having a backow
preventer in the cold water supply line, means
shall be provided to control thermal expansion.
Contact the water supplier or local plumbing
inspector on how to control thermal expansion.
• Should overheang occur or the gas supply fail to
shut o, turn o the manual gas control valve to
the appliance.
• Keep the air intake locaon free of chemicals, such
as chlorine or bleach, that produce fumes. These
fumes can damage components and reduce the life
of your appliance.
EARTHQUAKE STRAPPING
STRAP
Plasc Enclosure
(Side)
Plasc Enclosure
(Boom)
STRAP
NOTICE
Product installed in the state of California must be
braced, anchored, or otherwise secured to avoid moon
or falling during an earthquake. Contact the California
Oce of the State Architect located at 1102 Q Street,
Suite 5100, Sacramento, CA 95811 for instrucons.
1. Loosen screws along the perimeter of the plasc
enclosures
2. Remove plasc enclosures
3. Posion straps around the Demand Duo tank per
the requirements of California Oce of the State
Architect. DO NOT POSITION STRAPS OVER PIPE,
FITTINGS or WIRE.
4. Replace the plasc enclosures. (Modicaon of
the plasc enclosures may be necessary to t the
enclosures over the earthquake straps.)
5. Replace the screws around the perimeter of the
plasc enclosures.

6 Demand Duo™ 80
Determine Installaon Locaon
You must ensure that clearances will be met and that
the vent length will be within required limits. Consider
the installaon environment, water quality, and need
for freeze protecon. Requirements for the gas line,
water lines, electrical connecon, and condensate
disposal can be found in their respecve installaon
secons of this manual.
Minimum Clearances
The minimum clearances from both combusbles and
non-combusbles construcon is:
• 0 inches from the sides
• 0 inches from the back
• 12 inches from the top
• 6 inches from the front
• 0 inches from vent components and condensate
drain line.
*The clearance for servicing is 24 inches in front of the
water heater.
**The clearance for servicing the anode rods is
54 inches from the top of the water heater.
Checklist to Determine Installaon
Locaon
□The water heater is not exposed to corrosive
compounds in the air.
□The water heater locaon complies with the
clearances.
□For indoor models, the planned venng will not
exceed the maximum length for the number of
elbows used.
□The planned venng terminaon/air intake
locaon meets the clearances.
□Indoor air is not being used for combuson.
□The water supply does not contain chemicals or
exceed total hardness that will damage the heat
exchanger.
□The installaon must conform with local codes or,
in the absence of local codes, with the Naonal
Fuel Gas Code, ANSI Z223.1/NFPA 54, or the
Natural Gas and Propane Installaon Code, CSA
B149.1.
□Leave the enre manual taped to the water
heater, or give the enre manual directly to the
consumer.
• Choose the right hand truck to support the weight
and size of the water heater. Refer to the
“Specicaons” secon in this manual for specic
weights and dimensions.
• Use proper liing techniques to load the water
heater onto the hand truck:
• Posion the water heater onto the hand truck so
the weight is evenly balanced and the tank is
touching the rails of the hand truck.
• Secure the water heater to the hand truck:
 Posion STRAP A around the tankless unit as
illustrated below.
 Posion STRAP B around the base of the tank
below the LOWER ENCLOSURE.
Strap A
Strap B
Lower
Enclosure
Door

Demand Duo™ 80 7
REFER TO THE RL94 MANUAL FOR SPECIFIC DETAILS ON:
• Approved Vent Manufacturers and Terminaons
• Terminaon Clearances
• Maximum Vent Length
• Flue Installaon with Concentric Venng
• Consumer Operaon Guidelines for the Safe Operaon of your
Water Heater
• How to use the RL94 Temperature Controller
• RL94 Diagnosc Codes
• RL94 Required Maintenance (Draining of the tankless water heater will
require the lower enclosure to be removed. Reference page 17 to remove the enclosure.)
• RL94 Replacement Parts

8 Demand Duo™ 80
Installaon of Gas Supply
MUST DO
• A manual gas valve must be placed in the gas
supply line to the water heater. Install a union
between the gas valve and the appliance for future
servicing or unit removal.
• Check the type of gas and the gas inlet pressure
before connecng the water heater. If the water
heater is not of the gas type that the building is
supplied with, DO NOT connect the water heater.
Contact the dealer for the proper unit to match the
gas type.
• Check the gas supply pressure immediately
upstream at a locaon provided by the gas
company. Supplied gas pressure must be within
the limits shown in the Specicaons secon with
all gas appliances operang.
• Before placing the appliance in operaon all joints
including the heater must be checked for gas
ghtness by means of leak detector soluon, soap
and water, or an equivalent nonammable
soluon, as applicable. (Since some leak test
soluons, including soap and water, may cause
corrosion or stress cracking, the piping shall be
rinsed with water aer tesng, unless it has been
determined that the leak test soluon is non-
corrosive.)
• Use approved connectors to connect the unit to
the gas line. Purge the gas line of any debris before
connecon to the water heater.
• Any compound used on the threaded joint of the
gas piping shall be a type which resists the acon of
liqueed petroleum gas (propane/LPG).
• The gas supply line shall be gas ght, sized, and so
installed as to provide a supply of gas sucient to
meet the maximum demand of the heater and all
other gas consuming appliances at the locaon
without loss of pressure.
• Always check all gas pipe connecons and ngs
for leaks before operang the water heater. Use
soapy water on all ng and visually inspect for
bubble formaon. Rinse o soapy water and wipe
dry.
General Instrucons
WARNING
In order to access the gas connecons, remove the
plasc rivet screws that aach the lower enclosure to
the assembly. Proceed to then remove the lower
enclosure.
Gas Connecon
(3/4” MNPT)
Lower Enclosure
REFER TO THE RL94 MANUAL FOR
SPECIFIC DETAILS ON SIZING THE
GAS PIPE.
Gas
Valve
Union
1. If you are not knowledgeable or qualied to
install gas lines or connecons, then contact a
licensed professional to install the gas supply.
2. Turn o 120v power supply.
3. Turn o the gas.
4. Gas is ammable. Do not smoke or provide other
ignion sources while working with gas.
5. Do not turn on the water heater or gas unl all
fumes are gone.

Demand Duo™ 80 9
Connect Electricity
Do not rely on the gas or water piping to ground the
water heater. A terminal block inside the controller
should be used for the grounding connecon.
The water heater requires 120 VAC, 60 Hz power from
a properly grounded circuit.
The wiring diagram is located on the Technical Sheet
aached to the inside of the front cover.
WARNING
Do not use an extension cord or an adapter plug with
this appliance.
The water heang system must be electrically
grounded in accordance with local codes and
ordinances or, in the absence of local codes, in
accordance with the Naonal Electrical Code, ANSI/
NFPA No. 70.
The tankless water heater is equipped with a three-
prong (grounding) plug for your protecon against
shock hazard and should be plugged directly into the
three-prong receptacle located at the boom of the
controller.
REFER TO THE RL94 MANUAL FOR :
• High Altude Adjustment
• Vent Length Adjustment
• Temperature Controller Installaon
Low Voltage Ther-
mistors
Terminal
Block
Green
White
Black
Green
White
Black
DO NOT connect power to the commercial hybrid
system prior to compleng installaon and the
system has been lled with water.
ATTENTION
Green White
Black
PRE-WIRED PUMP
CONNECTION PRE-WIRED
SUPPLY POWER
Power Supply
Pump Control
Output: 120 Volt
Supply Power
Input: 120 Volt
(3 Prong Plug)
Tankless Supply
Output: 120 Volt
(3 Prong Receptacle
already connected to
tankless from factory)
Do not rely on the gas or water piping to ground the
water heater. A terminal block inside the controller
should be used for the grounding connecon.
The water heater requires 120 VAC, 60 Hz power from
a properly grounded circuit.
The wiring diagram is located on the Technical Sheet
aached to the inside of the front cover.

10 Demand Duo™ 80
SYSTEM CONTROLLER
NORMAL OPERATION (SLOW PULSE)
THERMISTOR ERROR (RAPID PULSE)
PUMP ON (SOLID GREEN LIGHT)
PUMP OFF (NO LIGHT)
Checklist for Gas and Electricity
□A manual gas control valve is placed in the gas
line to the water heater.
□Check the gas lines and connecons for leaks.
□Conrm that the gas inlet pressure is within
limits.
□Conrm that the water heater is rated for the gas
type supplied.
□Conrm that the electricity is supplied from 120
VAC, 60 Hz power source and is in a properly
grounded circuit.
□Conrm that an extension cord or an adapter plug
has NOT been used with the water heater.
The system controller maintains communicaon
between the tank and tankless to eecvely control
the tank temperature based on the selected
temperature on the tankless unit.
By reading the tank temperature (J22) and tankless
outlet temperature (J2), the System Controller will
energize (120V) the pump when the tank
temperature drops. When the tank temperature
returns to the selected set temperature the System
Controller will de-energize the pump and remain in
standby unl the tank temperature drops again.
When power is supplied, the System Controller will
maintain pump operaon. If system is not in use for
an extended period of me, Disconnect power from
the system.
ATTENTION
CONTROLLER DIAGNOSTICS

Demand Duo™ 80 11
Installaon of Plumbing
Pressure Relief Valve Requirements
An approved pressure relief valve (preinstalled) is
required by the American Naonal Standard (ANSI
Z21.10.3) for all water heang systems and shall be
accessible for servicing.
DO NOT
• Do not plug the relief valve and do not install any
reducing ngs or other restricons in the relief
line. The relief line should allow for complete
drainage of the valve and the line.
• Do not place any other type valve or shuto device
between the relief valve and the water heater.
MUST DO
• The relief valve must comply with the standard for
Relief Valves and Automac Gas Shuto Devices
for
Hot Water Supply Systems ANSI Z21.22 and /or the
standard Temperature, Pressure, Temperature and
Pressure Relief Valves and Vacuum Relief Valves,
CAN1-4.4.
• The pressure relief valve must be rated up to 150
psi and to at least the maximum BTU/hr of the
appliance.
• The discharge from the pressure relief valve should
be piped to the ground or into a drain system per
local codes.
• The pressure relief valve must be manually
operated once a year to check for correct
operaon.
• The relief valve should be added to the hot water
outlet line and near the hot water outlet according
to the manufacturer’s instrucons. DO NOT place
any other type valve or shut o device between
the relief valve and the water heater.
INFORMATION
If a relief valve discharges periodically, this may be due
to thermal expansion in a closed water supply system.
Contact the water supplier or local plumbing inspector
on how to correct this situaon. Do not plug the relief
valve.
Install the Temperature-Pressure Relief (T&P) Valve
according to these instrucons.
The tank poron of this system is provided with a
combinaon temperature-pressure relief valve. For
safe operaon of the water heater, the relief valve(s)
must not be removed from its designated point of
installaon or plugged.
An approved Temperature-Pressure Relief Valve is
required by the American Naonal Standard (ANSI
Z21.10.3) for all water heang systems, and shall be
accessible for servicing.
DO NOT
• Do not plug the T&P valve and do not install any
reducing ngs or other restricons in the relief
line. The relief line should allow for complete
drainage of the T&P valve and the line.
• Do not place any other type valve or shut o
device between the relief valve and the water
heater.
• Do not pipe temperature-pressure relief valve,
pressure relief valve, and/or condensate drain
together into a common pipe.
MUST DO
• The T&P valve must comply with the standard for
Relief Valves and Automac Gas Shuto Devices
for Hot Water Supply Systems ANSI Z21.22 and /or
the standard Temperature, Pressure, Temperature
and Pressure Relief Valves and Vacuum Relief
Valves, CAN1-4.4.
• The T&P valve must be rated up to 150 psi and to
at least the maximum BTU/hr of the appliance.
• The discharge from the T&P Valve should be
piped to the ground or into a drain system to
prevent exposure or possible burn hazards to
humans or other plant or animal life. Follow local
codes. Water discharged from the relief valve
could cause severe burns instantly, scalds, or
death.
• The Temperature-Pressure Relief Valve must be
manually operated once a year to check for
correct operaon.
Temperature-Pressure Relief Valve
Requirements
WARNING
Water discharged from the pressure relief valve
could cause severe burns instantly or death from
scalds.

12 Demand Duo™ 80
AHot Water Outlet *
BHot Water Outlet Valve *
CTemperature-Pressure Relief Valve
DCold and Hot Unions *
ECold Water Supply Valve *
FCold Water Supply *
GThermal Expansion Tank *
HVent pipe (concentric shown for illus-
traon purposes, see venng secon
for other opons)
*
IOperaon Unit / Temperature Control
JDrain Pan *
KTemperature-Pressure Relief Valve
Discharge Pipe (do not cap,
plug, or reduce )
*
LDrip Leg (Sediment Trap) *
MGas Union *
NGas Control Valve
OThermostac Mixing Valve *
PNon-Tempered Return Line *
QNon-Tempered Supply Line *
Typical Installaons
* Field Supplied
Mixing Valve Installaon
Hot Water
Supply
A
B
H
D
C
I
K
J
E
N
M
L
Cold Water
Supply
Q
O
P
D
F
G

Demand Duo™ 80 13
Piping Diagram for Basic Installaons
Commercial Hybrid
Single Unit Circulaon
Note:
Installaon must conform to applicable code
and all requirements listed in the installaon
manual. Balancing valves, equivalent piping,
pressure gauges, and temperature gauges are
to be used as necessary to ensure proper ow
between units.
Condensate piping shall be CPVC or PVC
material and shall not be smaller than the drain
connecon on the appliance.
Components of condensate drainage shall be
CPVC or PVC material. All components shall be
selected for the pressure and temperature
rang of the installaon.
Where the drain pipes from more than one unit
are manifolded together for condensate
drainage, the pipe or tubing shall be sized in
accordance with an approved method as
dictated by local codes.
Condensate must be disposed of according to
local codes. Gas Supply
Cold Water Supply
Tankless PRV
Tank T&P
Pipe T&P to Open Drain Pipe Condensate to Open Drain
Hot Water Supply Line
Building
Circulaon
Pump Building Hot Water
Return Line
(Oponal)
Condensate Drain Line
3in (75 mm)
minimum

14 Demand Duo™ 80
Piping Diagram for Mulple Unit Installaons
Notes: • Installaon must conform to applicable code and all requirements listed in the installaon manual. Balancing valves, equivalent piping, pressure
gages, and temperature gages are to be used as necessary to ensure proper ow between units.
• Condensate piping shall be CPVC or PVC material and shall not be smaller than the drain connecon on the appliance. • Components of the condensate drainage shall be CPVC or PVC material. All components shall be selected for the pressure and temperature rang
of the installaon.
• Where the drain pipes from more than one unit are manifolded together for condensate drainage, the pipe or tubing shall be sized in accordance
with an approved method as dictated by local codes.
• Condensate must be disposed of according to local codes.
BUILDING CIRCULATION PUMP AND HOT WATER RETURN LINE (OPTIONAL)
Addional units can be installed as illustrated. PIPE EACH T&P AND PRV
TO OPEN DRAIN
Gas Supply
Cold Water Supply
Hot Water Supply Line

Demand Duo™ 80 15
Connect Water Heater to Water Supply
Water connecons to the Commercial Hybrid System
should follow all state and local plumbing codes.
If this is a standard installaon, refer to the Piping
Diagram for basic installaon.
1. Use of this layout should provide a trouble-free
installaon for the life of the water heater. Before
making the plumbing connecons, locate the
COLD water inlet and the HOT water outlet.
• The COLD water inlet is a 1.5” MNPT ng on
the lower poron of the tank below the
tankless unit.
• The HOT water outlet is a 1.5” MNPT ng
located at the top of the tank. Install a shut-
o valve close to the water heater in the cold
water line. It is recommended that unions be
installed in the cold and hot water lines so
that the water heater can be easily discon-
nected, if servicing is required.
2. When assembling the hot and cold piping, use a
good food grade pipe joint compound, and ensure
all ngs are ght. It is imperave that open
ame is not applied to the inlet and outlet ngs,
as heat will damage or destroy the plasc lined
ngs. This will result in premature failure of
the ngs, which is not covered by the
warranty.
□Ensure that hot and cold water lines are not
crossed to the unit and are leak free.
□Ensure that a pressure relief valve is installed with
a rang that exceeds the BTU input of the water
heater model. Refer to the rang plate on the
side of the water heater for BTU input.
□Clean the inlet water lter by closing the cold and
hot water inlet isolaon (shut-o) valves. Put a
bucket under the lter at the boom of the water
heater to catch any water that is contained inside
the unit. Unscrew the water lter. Rinse the
lter to remove any debris. Install the lter and
open the isolaon valves.
□Check for proper water pressure to the water
heater. Minimum water pressure is 50 psi. Rinnai
recommends 60-80 psi for maximum
performance.
□ Ensure any issues regarding water quality have
been properly addressed.
DO NOT OPERATE THIS WATER HEATER UNLESS IT IS
COMPLETELY FULL OF WATER. To prevent damage to
the water heater, all air must be relieved from the
system and a hot water xture must be owing water
before the water heater is plugged in and turned on.
To ensure safe and eecve operaon of the water
heater, use the following lling procedure. To ll the
water heater:
1. Ensure the drain valve located at the boom of
the tank is closed.
2. Open the nearest hot water xture in the
plumbing system.
3. Open the cold water supply valve to the water
heater.
4. Keep the hot water xture open unl the tank is
lled and constant ow is obtained at the xture.
5. Check water heater connecons and plumbing
system for damage or leaks. Repair if needed.
Filling the System
Checklist for Plumbing
NOTICE
DO NOT OPERATE THIS WATER HEATER UNLESS IT IS
COMPLETELY FULL OF WATER

16 Demand Duo™ 80
[1] A vent shall not terminate directly above a sidewalk or paved driveway
that is located between two single family dwellings and serves both
dwellings.
[2] Permied only if veranda, porch, deck, or balcony is fully open on a
minimum of two sides beneath the oor.
 For clearances not specied in ANSI Z223.1/NFPA 54, clearances are in
accordance with local installaon codes and the requirements of the gas
supplier.
Clearance to opposite wall is 24 inches (60 cm).
A vent terminaon must be installed to bring in combuson air and expel exhaust to the outside.
Ref Descripon Canadian Installaons US Installaons
AClearance above grade, veranda, porch, deck, or balcony 12 inches (30 cm) 12 inches (30 cm)
BClearance to window or door that may be opened 36 inches (91 cm) 12 inches (30 cm)
CClearance to permanently closed window **
DVercal clearance to venlated sot, located above the terminal within a * *
EClearance to unvenlated sot **
FClearance to outside corner **
GClearance to inside corner **
HClearance to each side of center line extended above meter/regulator
assembly **
IClearance to service regulator vent outlet
Above a regulator within 3  (91cm)
horizontally of the vercal center line of
the regulator vent outlet to a maximum
vercal distance of 15  (4.5 m)
*
JClearance to nonmechanical air supply inlet to building or the combuson air
inlet to any other appliance 36 inches (91 cm) 12 inches (30 cm)
KClearance to a mechanical air supply inlet 6 feet (1.83 m) 3 feet (91 cm) above if within
10 feet (3 m) horizontally
LClearance above paved sidewalk or paved driveway located on public
property 7 feet (2.13 m) *
MClearance under veranda, porch, deck, or balcony 12 inches (30 cm)  *
Direct Vent Terminal Clearances
AIR SUPPLY INLET
VENT TERMINAL
AREA WHERE TERMINAL IS NOT PERMITTTED
SNOW
TERMINATION
Clearance in
Ref. A also
applies to
anticipated
snow line
X
V

Demand Duo™ 80 17
Venng Guidelines
DO NOT
• Do not use PVC/CPVC, ABS, or galvanized material
to vent this appliance.
• Do not cover non-metallic vent pipe and ngs
with thermal insulaon.
• Do not combine vent components from dierent
manufacturers.
• Vent diameter must not be reduced.
• Do not connect the venng system with an
exisng vent or chimney.
• Do not common vent the vent pipe of any other
manufacturer’s water heater or appliance.
MUST DO
• This water heater is a direct vent water heater and
therefore is cered and listed with the vent
system. You must use vent components that are
cered and listed with the water heater model.
• The vent system must vent directly to the outside
of the building and use outside air for combuson.
• Avoid dips or sags in horizontal vent runs by
installing supports per the vent manufacturer’s
instrucons.
• Support horizontal vent runs every four feet and
all vercal vent runs every six feet or in
accordance with local codes.
• Venng should be as direct as possible with a
minimum number of pipe ngs.
• Vent connecons must be rmly pressed together
so that the gaskets form an air ght seal.
• The vent piece connected to the water heater
must be secured with one self-tapping screw.
INFORMATION
• Refer to the instrucons of the vent system
manufacturer for component assembly
instrucons.
• If the vent system is to be enclosed, it is suggested
that the design of the enclosure shall permit
inspecon of the vent system. The design of such
enclosure shall be deemed acceptable by the
installer or the local inspector.
NOTICE
If it becomes necessary to access an enclosed vent
system for service or repairs, Rinnai is not
responsible for any costs or dicules in accessing
the vent system. The warranty does not cover
obtaining access to a vent system in an enclosed
environment.

18 Demand Duo™ 80
If the condensate collector is not used, the drain
pipe must be capped to prevent exhaust gases
and condensate from entering the building. The
cap is supplied on the appliance. In such an
instance slope the venng 1/4” per foot away
from appliance according to vent
manufacturer’s installaon instrucons.
Flue Installaon
Vercal Terminaon
(condensate collector must be used in all installaons)
3 in (75 mm)
minimum
3 in (75 mm)
minimum
Horizontal Terminaon using Condensate Collector
3 in (75 mm)
minimum
Condensate
To adjust the condensate collector posion or to
replace the female vent top with a male vent top:
1. Loosen the 4 screws at the rear bracket
2. Slide the bracket away from the female vent top.
3. Remove the 4 screws aaching the female vent top
to the water heater.
4. Li up the female vent top and reposion as desired
(or replace with a male vent top).
5. Install the 4 screws at the vent top and ghten the 4
screws at the bracket.
Secure the rst vent component to the water heater
with one self-tapping screw at the hole located above
the condensate collector.
Bracket
Condensate Collector
Securing Screw
Horizontal Terminaon without using the Condensate Collector
Maximum Height *
5 feet (1.52 m) Regions of cold climate will create more
condensate in the vent system. The
condensate collector should be used in
cold climates.
If more than one elbow is used in the
vercal secon the condensate collector
must be used.
* The condensate collector must be used in
horizontal terminaons if a vercal rise in
the vent system exceeds 5.
WARNING
Install the venng terminaon according to the diagrams and instrucons below.
Slope the venting 1/4” per foot toward
the appliance according to the vent
manufacturers installation instructions.
Dispose of condensate per local codes.

Demand Duo™ 80 19
Condensate
Condensate can form in the vent of high eciency
direct vent appliances. Without proper drainage,
condensate will damage the heat exchanger.
To prevent condensate damage, follow these
instrucons.
DO NOT
• Do not allow condensate to enter the water
heater.
• Do not connect the condensate drain pipe directly
to the rain sewer.
• Do not connect the condensate drain line with an
air condioning evaporator coil drain or.
• Do not connect the condensate drain line to the
pressure relief valve/line of the appliance.
MUST DO
• Use only venng that is approved and idened as
acceptable for your parcular model.
• For vercal terminaons, install a condensate drain
and trap as close as possible to the appliance.
• Slope the venng 1/4” per foot toward the
appliance according to the vent manufacturers
installaon instrucons. Dispose of condensate per
local codes.
• All condensate must drain and be disposed of
according to local codes.
• If the condensate collector is not used, the drain
pipe must be capped to prevent exhaust gases and
condensate from entering the building. The cap is
supplied on the appliance. In such an instance
slope the venng 1/4” per foot away from
appliance according to vent manufacturer’s
installaon instrucons.
• Use only corrosion resistant materials for the
condensate drain lines such as PVC pipe or plasc
hose.
• The condensate drain pipe (along its enre length)
must be at least the same diameter as the drain
line, (5/8 inch NPT).
Checklist for Venng and
Condensate (indoor models only)
□Verify proper clearances around the vent
terminaons and air intakes.
□Ensure you have used the correct venng
products for the model installed and that you
have completely followed the venng
manufacturer’s installaon instrucons and these
installaon instrucons.
□Verify that the vent pipe has a downward slope or
grade to the outside of 1/4 inch per foot (1.2° )
OR if the vent pipe is sloped toward the water
heater (as some local codes require), that a
condensate collector is installed to allow
condensaon to drain away from the water
heater to a proper drain source.
□Verify that condensate will not be allowed to
drain back into the water heater.
□Verify that the vent system does not exceed the
maximum length for the number of elbows used.
• The end of the condensate drain pipe should be
open to the atmosphere. The end should not be
under water or other substances.
• To minimize freezing of the condensate, run the
condensate drain line through an interior wall or
between insulaon and an interior wall.
• The condensate collector should be used for all
combinaon domesc/hydronic heang
applicaons.
INFORMATION
• A condensate trap is available, P/N 222053.
• Regions of cold climate will create more
condensate in the vent system. The condensate
collector should be used in cold climates.
• The condensate drain pipe should be as short as
possible and have a downward pitch.

20 Demand Duo™ 80
Final Checklist
□The water heater is not subject to corrosive
compounds in the air.
□The water supply does not contain chemicals or
exceed total hardness that will damage the heat
exchanger.
□Clearances from the water heater unit are met.
□Clearances from the vent terminaon / air intake
are met.
□Ensure you have used the correct venng
products for the model installed and that you
have completely followed the venng
manufacturer’s installaon instrucons and these
installaon instrucons.
□Verify that the vent system does not exceed the
maximum length for the number of elbows used.
□Verify that SW 1 in DIPSW 1 has been adjusted for
vent length if necessary. Refer to the secon on
Maximum Vent Length.
□Purge the water line of all debris and air by
closing the hot isolaon valve and opening the
cold isolaon valve and its drain. Debris will
damage the water heater. Use a bucket or hose
if necessary.
□Ensure that hot and cold water lines are not
crossed to the unit and are leak free.
□A manual gas control valve has been placed in the
gas line to the water heater.
□Ensure that a pressure relief valve is installed with
a rang that exceeds the BTU input of the water
heater model. Refer to the rang plate on the
side of the water heater for BTU input.
□Clean the inlet water lter by closing the cold and
hot water inlet isolaon (shut-o) valves. Put a
bucket under the lter at the boom of the water
heater to catch any water that is contained inside
the unit. Unscrew the water lter. Rinse the
lter to remove any debris. Install the lter and
open the isolaon valves.
□Check the gas lines and connecons for leaks.
□Conrm that the gas inlet pressure is within
limits.
□Conrm that the water heater is rated for the gas
type supplied.
□Conrm that the electricity is supplied from a 120
VAC, 60 Hz power source, is in a properly
grounded circuit, and turned on.
□Verify the temperature controller is funconing
properly.
□Verify that SW 2 and SW 3 in DIPSW 1 is set
correctly for your altude.
□Verify the system is funconing correctly by
connecng your manometer to the gas pressure
test port on the water heater. Operate all gas
appliances in the home or facility at high re. The
inlet gas pressure at the water heater must not
drop below that listed on the rang plate.
□DO NOT introduce toxic chemicals such as those
used for boiler water treatment to the potable
water used for space heang.
□If the water heater is not needed for immediate
use, then drain the water from the heat
exchanger.
□Install the front panel.
□Explain to the customer the importance of not
blocking the vent terminaon or air intake.
□Explain to the customer the operaon of the
water heater, safety guidelines, maintenance, and
warranty.
□The installaon must conform with local codes or,
in the absence of local codes, with the Naonal
Fuel Gas Code, ANSI Z223.1/NFPA 54, or the
Natural Gas and Propane Installaon Code, CSA
B149.1.
□Leave this manual and the enre RL94 manual
taped to the water heater, or give both manuals
directly to the consumer.