Rinnai Circ-Logic RU98i User manual

1Rinnai CVent
Common Vent Installaon Manual
For the RU98i (REU-KB3237FFUD-US), RUC98i (REU-KBD3237FFUD-US), and
C199i (REU-KBD3237FFUDC-US) Condensing Water Heaters
This manual is a supplement to the appliance manual.
Addional informaon can be obtained from the Rinnai Water Heater 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 licensed professional.
If the informaon in these instrucons is not followed exactly, a re or explosion
may result causing property damage, personal injury or death.
WARNING
Certified to ANSI Z21.10.3 - CSA 4.3
For U.S. and Canadian Installations
This enre manual must be le for the consumer. The consumer must read and
refer to this manual for proper operaon and maintenance of the common vent system.
CUS

Rinnai CVent 2
Descripon
The CVent Common Venng system provides longer vent lengths and fewer wall or roof penetraons than
convenonal single-unit venng. For the exhaust ue, CVent ulizes a CSA cered and tested venng (PPTL)
and for Canada ULC-S636-cered and tested venng (PPS) material from Ubbink, the same supplier for
Rinnai's innovave line of concentric venng. The various secons are self locking and sealing and can be
pushed together without use of cement or glue.
CVent is for use in U.S. and Canada only. PPTL components are cered for U.S. installaons whereas PPS
components are cered for Canadian installaons.
Installaon is cered for up to 10,200 feet. Refer to the Installaon and Operaon Manual for the tankless
water heater (RU98i, RUC98i or C199i) for appropriate dip switch selecon. Refer to High Altude
Installaon secon in this manual for appropriate de-rate values.
Model Applicability
The common vent system is CSA cered (ANSI Z21.10.3, Gas Water Heaters Standards) for use with the
following Rinnai tankless condensing water heaters only: RU98i (REU-KB3237FFUD-US),
RUC98i (REU-KBD3237FFUD-US), and C199i (REU-KBD3237FFUDC-US)
Installer Qualicaons .......................................... 2
Descripon............................................................ 2
Model Applicability............................................... 2
Safety Symbols...................................................... 3
Warranty and Liability Exclusions ......................... 3
Specicaons ........................................................ 3
High Altude Installaon ...................................... 4
Parts/Kits............................................................... 5
Sample Roof Installaon..................................... 13
Sample Horizontal Terminaon Installaon……..14
Sample Vercal Terminaon Installaon……...….15
Venng Guidelines.............................................. 16
Maximum Equivalent Vent Length...................... 17
CVent Terminaon Clearances............................17
Combuson Air Requirements ...........................19
Exhaust Vent Terminaon Clearances ................23
CVent Maintenance Clearances ..........................26
Water Heater Clearances....................................26
CVent Installaon Instrucons............................27
Common Header Check valve Maintenance....... 32
Final Checklist......................................................33
Appendix
Ubbink CVent Assembly Instrucons..................34
French Version ....................................................44
Installer Qualicaons
Table of Contents
Improper installaon of the vent system and components, or failure to follow all installaon
instrucons, can result in serious injury.
WARNING
A licensed professional must install the common venng.
The installer should have skills such as
 connecng gas lines, water lines, valves, and electricity
 knowledge of applicable naonal, state, and local codes
If you lack these skills, contact a licensed professional.

3Rinnai CVent
Indicates an imminently hazardous situaon which, if not avoided, will result in death or
serious injury.
Indicates a potenally hazardous situaon which, if not avoided, could result in death or
serious injury.
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.
This is the safety alert symbol. This symbol alerts you to potenal hazards that can kill or hurt you and
others.
DANGER
CAUTION
WARNING
Safety Symbols
Claims for personal and material damages are excluded, if they are due to any or several of the following
reasons:
•Use of the Cvent system not in accordance with the regulaons.
•Improper assembly and incorrect operaon.
•Faulty maintenance.
•Non-compliance with the assembly and operang instrucons.
•Non-approved structural changes to the unit or to the individual components.
•Installaon of components which are not part of the Cvent system .
•Subsequent damage, which occurred through further use of the Cvent system despite known defects.
•Intenonal damage.
•Force Majeure.
Warranty and Liability Exclusions
Specicaons
Number of
water
heaters*
Percent
De-rated Total Btu Rate
Btu at
Minimum Rate
(without MSB)
Btu at
Minimum Rate
(with MSB)
10% 199,000 15,200
15,200
21% 394,000 30,400
31.5% 588,000 45,600
42% 780,000 60,800
52.5% 970,000 76,000
63% 1,158,000 91,200
73.5% 1,344,000 106,400
84% 1,528,000 121,600
RU98i (REU-KB3237FFUD-US), RUC98i (REU-KBD3237FFUD-US), and C199i (REU-KBD3237FFUDC-US)
Altude: 0-2,000 feet
Natural and propane gas
The RU98i and RUC98i units are cered for direct vent only. The C199i is cered for both direct vent and exhaust
only with room air when installed in a commercial common vent applicaon only. Water heaters using CVent will
automacally de-rate according to the table below. Use the table below for calculang your total Btu for mulple
water heaters using CVent.

4Rinnai CVent
Water Heater Installaon
For informaon regarding the installaon of the RU98i (REU-KB3237FFUD-US), RUC98i (REU-KBD3237FFUD-US), and
C199i (REU-KBD3237FFUDC-US) tankless water heaters, please reference the Installaon and Operaon Manual
included with the respecve tankless water heater.
Set the water heater for “Long Vent” by adjusting the SW1 in DIPSW1 to the OFF Position. (Must be done on all tankless
water heaters when using CVent System)
High Altude Installaons
The Rinnai RU98i (REU-KB3237FFUD-US), RUC98i (REU-KBD3237FFUD-US), and C199i (REU-KBD3237FFUDC-US) tank-
less water heaters have been cered for use with the Common Vent System (CVent) at installaons from
0 - 10,200 feet. (0 - 3,109 m). The Common Vent System is ANSI Z21.10.3 cered; exhaust components to be
propylene (PP/PPTL) for U.S. installaons and PPS for Canadian installaons (all venng components used in Canada
must be ULC-S636 cered). Intake components to be in accordance with naonal and/or local codes having
jurisdicon.
For CVent installaons at high altude you must ensure that the water heaters are properly installed and setup for the
altude that they will be operang at. For informaon on how to adjust altude sengs reference the respecve In-
stallaon and Operaon Manual for the RU98i (REU-KB3237FFUD-US), RUC98i (REU-KBD3237FFUD-US), and
C199i (REU-KBD3237FFUDC-US) tankless water heaters.
Water heaters using CVent at altudes over 2,000 will automacally de-rate according to the table below. Use the
tables below for calculang your total Btu for mulple water heaters using CVent at elevaon:
* RU98i (REU-KB3237FFUD-US), RUC98i (REU-KBD3237FFUD-US), and C199i (REU-KBD3237FFUDC-US)
Altude: 2,001-10,200 feet
Natural and propane gas
High Altude De-Rate plus Cvent De-Rate - LP Gas
Number
of Water
Heaters 2001-5200 Ft 5201 - 7700 Ft 7701 - 10200 Ft
1168,000 151,000 120,000
2332,640 298,980 237,600
3493,920 443,940 352,800
4651,840 585,880 465,600
5806,400 724,800 576,000
6957,600 860,700 684,000
71,105,440 993,580 789,600
81,249,920 1,123,440 892,800
High Altude De-Rate plus Cvent De-Rate - Natural Gas
Number
of Water
Heaters 2001-5200 Ft 5201 - 7700 Ft 7701 - 10200 Ft
1170,000 153,000 139,000
2336,600 302,940 275,220
3499,800 449,820 408,660
4659,600 593,640 539,320
5816,000 734,400 667,200
6969,000 872,100 792,300
71,118,600 1,006,740 914,620
81,264,800 1,138,320 1,034,160

5Rinnai CVent
Direct Vent 8" Common Venng
Direct Vent Common Venng Descripon U.S. (PPtl) Canada (PPs)
Item Number Item Number
8" back-to-back 3 unit header kit CV8BB3USDV CV8BB3CADV
8" back-to-back 4 unit header kit CV8BB4USDV CV8BB4CADV
8" back-to-back 5 unit header kit CV8BB5USDV CV8BB5CADV
8" back-to-back 6 unit header kit CV8BB6USDV CV8BB6CADV
8" back-to-back 7 unit header kit CV8BB7USDV CV8BB7CADV
8" back-to-back 8 unit header kit CV8BB8USDV CV8BB8CADV
8" in-line 3 unit header kit CV8IL3USDV CV8IL3CADV
8" in-line 4 unit header kit CV8IL4USDV CV8IL4CADV
8" in-line 5 unit header kit CV8IL5USDV CV8IL5CADV
8" in-line 6 unit header kit CV8IL6USDV CV8IL6CADV
8" in-line 7 unit header kit CV8IL7USDV CV8IL7CADV
8" in-line 8 unit header kit CV8IL8USDV CV8IL8CADV
Back-to-Back
Conguraon In-line
Conguraon
These header kits include all of the components needed to fully assemble intake and exhaust headers. Extension
kits are purchased separately.

Rinnai CVent 6
Room Air 8" Common Venng
Room Air Common Venng Descripon U.S. (PPtl) Canada (PPs)
Item Number Item Number
8" back-to-back 3 unit header kit CV8BB3USRA CV8BB3CARA
8" back-to-back 4 unit header kit CV8BB4USRA CV8BB4CARA
8" back-to-back 5 unit header kit CV8BB5USRA CV8BB5CARA
8" back-to-back 6 unit header kit CV8BB6USRA CV8BB6CARA
8" back-to-back 7 unit header kit CV8BB7USRA CV8BB7CARA
8" back-to-back 8 unit header kit CV8BB8USRA CV8BB8CARA
8" in-line 3 unit header kit CV8IL3USRA CV8IL3CARA
8" in-line 4 unit header kit CV8IL4USRA CV8IL4CARA
8" in-line 5 unit header kit CV8IL5USRA CV8IL5CARA
8" in-line 6 unit header kit CV8IL6USRA CV8IL6CARA
8" in-line 7 unit header kit CV8IL7USRA CV8IL7CARA
8" in-line 8 unit header kit CV8IL8USRA CV8IL8CARA
Back-to-Back
Conguraon
In-line
Conguraon
(Room air is only for C199i in Commercial Common Vent Applicaons)

7Rinnai CVent
CVent Starter Kit
790005 / 791008PPS*
8-Inch For Back-to-Back or In-line
Combustion Air & Exhaust
123
4
CVent In-line Kit
790007 / 791009PPS*
8-Inch Header Kit For In-line
Combustion Air & Exhaust
124
3
6
NO QTY DESCRIPTION PPTL PART #’S *PPS PART #’S
11CVENT ENDPIECE (EXHAUST) W/ CLEANOUT & CONDENSATE DRAIN (32mm) 790042 NA
21CVENT COMB AIR ENDPIECE D8 780046 NA
31CVENT CONDENSATE TRAP (32mm Connection) 790048 NA
41CVENT DRAIN HOSE AND CLAMPS 790049 NA
61UBBINK INSTALLATION INSTRUCTION NA NA
71CENTROCERIN LUBRICANT NA NA
NO QTY DESCRIPTION PPTL PART #’S *PPS PART #’S
11CVENT COLLECTOR, 1 CONNECTION, D8 X L20 X D4 (Exhaust) 790040 NA
21CVENT ELBOW D4 X 87° WITH CLEANOUT 790039 NA
31CVENT EXTENSION, D4 X L18 790035 NA
41CVENT APPLIANCE ADAPTER WITH CHECK VALVE AND HOSE TRAP 790038 NA
51CVENT COMB. AIR COLLECTOR, 1 CONNECTION, D8 X L20 X D3 780044 NA
61CVENT COMB AIR FLEX FITTING, D3 780050 NA
71CENTROCERIN LUBRICANT NA NA
Ø4”
7
7
Ø3”
5
*PPS kits and components
are cered for use in
Canada
*PPS kits and components are
cered for use in Canada

Rinnai CVent 8
CVent Back-2-Back Kit
790008 / 791010PPS
8-Inch Header Kit For Back-to-Back
Combustion Air & Exhaust
NO QTY DESCRIPTION PPTL PART #’S *PPS PART #’S
11CVENT COLLECTOR, 2 CONNECTION, D8 X L20 790041 NA
22CVENT ELBOW D4 X 87° WITH CLEANOUT 790039 NA
32CVENT EXTENSION, D4 X L18 790035 NA
42CVENT APPLIANCE ADAPTER WITH CHECK VALVE AND 790038 NA
51CVENT COMB. AIR COLLECTOR, 2 CONNECTION, 780045 NA
62CVENT COMB. AIR FLEX FITTING, D3 780050 NA
71CENTROCERIN LUBRICANT NA NA
15
24
36
Ø4” Ø3”
Ø4” Ø3”
7
*PPS kits and components are
cered for use in Canada

9Rinnai CVent
CVent Starter Kit-Room Air
790058 / 791011PPS*
8-Inch For Back-to-Back or In-line
Combuson Air & Exhaust
(Room air is only for C199i in Commercial Common
Vent Applicaons)
CVent In-line Kit-Room Air
790059 / 791012PPS*
8-Inch Header Kit For In-line
Combuson Air & Exhaust
(Room air is only for C199i in Commercial Common Vent Applicaons)
NO QTY DESCRIPTION PPTL PART #’S *PPS PART #’S
11CVENT COLLECTOR, 1 CONNECTION, D8 X L20 X D4 (Exhaust) 790040 NA
21CVENT ELBOW D4 X 87° WITH CLEANOUT 790039 NA
31CVENT EXTENSION, D4 X L18 790035 NA
41CVENT APPLIANCE ADAPTER (ROOM AIR), CHECK VALVE, HOSE TRAP NA NA
51CENTROCERIN LUBRICANT NA NA
5
4
1
3
2
4
NO QTY DESCRIPTION PPTL PART #’S *PPS PART #’S
11CVENT ENDPIECE (EXHAUST) W/ CLEANOUT & CONDENSATE DRAIN (32mm) 790042 NA
21CVENT CONDENSATE TRAP (32mm Connection) 790048 NA
31CVENT DRAIN HOSE AND CLAMPS 790049 NA
51UBBINK INSTALLATION INSTRUCTION NA NA
61CENTROCERIN LUBRICANT NA NA
123
Ø4”
Ø4”
12
36
*PPS kits and components are
cered for use in Canada
*PPS kits and components are
cered for use in Canada

Rinnai CVent 10
CVent Back-to-Back Kit-Room Air
790060 / 791013PPS*
8-Inch Header Kit For Back-2-Back
Combuson Air & Exhaust
(Room air is only for C199i in Commercial Common Vent Applicaons)
NO QTY DESCRIPTION PPTL PART #’S *PPS PART #’S
11CVENT COLLECTOR, 2 CONNECTION, D8 X L20 790041 NA
22CVENT ELBOW D4 X 87° WITH CLEANOUT 790039 NA
32CVENT EXTENSION, D4 X L18 790035 NA
41CVENT APPLIANCE ADAPTER (ROOM AIR), CHECK VALVE, HOSE TRAP NA NA
51CENTROCERIN LUBRICANT NA NA
12
3
Ø4”
Ø4”
5
4
1
3
2
4
*PPS kits and components are
cered for use in Canada

11 Rinnai CVent
31” Ø12.2”
Ø0.24” (Qty. 4)
Interior Slip
Fit Wall Plate
Ø7.89”
Termination Kits
Cvent 8-in Wall Termination Kit (Combustion Air & Exhaust)
790004 (for use with PPtl and PPS material)
Centrocerin lubricant
(Material: Stainless Steel)
Cvent 8-in Roof Termination Kit 790057 / 791007PPS (can be used as Intake or Exhaust)
Centrocerin
Lubricant
CVent 8-in Roof Termination
(Outer shell: available in PPtl or PPS)
If roof terminaon is being used as intake the
assembly must include the intake rain cap

12 Rinnai CVent
COMMON VENT COMPONENTS
CVent 8-in Chase Cover
#790030
CVent Pitched Roof Flashing
(Including Storm Collar)
#790003
CVent Flat Roof
Flashing #790002
CVent 8in Vent Rain Cap
(Exhaust) #790034
Inverter Coupling Kit With Condensate Trap
#790032
CVent Elbow D8x45 degree
#790022 / 791002PPS (Qty.2)
CVent Elbow D8x90 degree
#790023 / 791003PPS
CVent Extension
D8xL18” #790020,
D8xL39” #790021 / 791001PPS
D8xL78” #790052 / 791006PPS
CVent Elbow D8x90 degree
Vertical Support #790029
CVent 8-in
Bracket #790024
CVent 8in Vent
Distancer #790031
Combustion Air PVC Adapter Kit
#780037
CVent 8in Vent Rain Cap
(Intake) #780053
CVent Extension
D4xL18” #790035 / 791004PPS
D8xL39” #790028

13 Rinnai CVent
Sample Roof Assembly
CVent 8-in Roof Termination
Kit with PVC Adapter
#7900057 / 791007PPS
Cvent pitched roof moldable
flashing #790003
Field Supplied
PVC Components
Field Supplied
8” PVC Flashing
CVent 8in Vent Rain Cap
(Exhaust) #790034
OPTIONAL
Vent termination per ANSI Z223.1/NFPA
54. For clearances not specified in ANSI
Z223.1/NFPA 54, clearances are in
accordance with local installation codes
and the requirements of the gas supplier.
Intake
Exhaust

14 Rinnai CVent
Part Number: 790008
CVent Back-to-Back Kit
Part Number:790020 / 790021
CVent Extension
Part Number:780037
Combustion Air PVC Adapter Kit
Part Number:790023
CVent Elbow D8 x 90
Part Number: 790005
CVent Starter Kit
Part Number:790004
Wall Termination Kit
Combustion Air & Exhaust
Field Supplied
PVC Components
Field Supplied
PVC Components
Sample Horizontal Termination Assembly
Complete Header Kit Pictured:
U.S.-CV8BB8USDV
Canada-CV8BB8CADV

15 Rinnai CVent
Sample Vertical Termination Assembly-Room Air (C199i Only)
Complete Header Kit (B-to-B):
U.S.-CV8BB6USRA
Canada-CV8BB6CARA
Complete Header Kit (In-line):
U.S.-CV8IL3USRA
Canada-CV8IL3CARA
Vent termination per ANSI Z223.1/NFPA 54. For
clearances not specified in ANSI Z223.1/NFPA 54,
clearances are in accordance with local installation
codes and the requirements of the gas supplier.
Part Number:790023
CVent Elbow D8 x 90
Part Number: 790005
CVent Starter Kit
Part Number: 790060
CVent Back-2-Back Kit
Part Number: 790057
CVent 8-in Roof Termination
Part Number:790020 / 790021
CVent Extension
CVENT APPLIANCE
ADAPTER WITH CHECK
VALVE AND TRAP

Rinnai CVent 16
Venng Guidelines
DO NOT
 Do not install in separate distribuon systems. All
water heaters common vented must be in the
same hot and cold plumbing manifolds and must
not exceed 8 units.
 Do not use PVC, CPVC, ABS or galvanized material
for the exhaust vent. CVent must ulize PPTL or
PPS on the exhaust side of the system.
 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 with the vent pipe of any
other type of water heater or appliance.
 Do not install the water heater in an area of
negave pressure.
 Do not install the water heater, venng, and vent
terminaon(s) in any areas where the air may
contain corrosive compounds.
MUST DO
•The water heater dip switch seng must always
be set to long vent (SW1 in DIPSW1 should be set
to OFF posion).
 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 or room air
(room air is for C199i commercial water heater
applicaons only) 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 a minimum of every
four feet and all vercal vent runs a minimum of
every six feet.
 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.
 Install an appliance adapter which contains a
check valve onto each water heater. Use only the
check valve specied in this manual. Do not
aempt to build your own system.
 The air intake appliance adapter connected to the
water heater must be secured with one self-
tapping screw.
 Check and clean the header check valve every 12
months according to the maintenance instrucons
in this manual.
 Set the temperature seng on all water heaters
being common vented to the same temperature.
INFORMATION
 Unless recovering a tank, Rinnai recommends
installing an MSB controller when common
venng and where water heaters are in a manifold
system.
 For assembly details, refer to the Ubbink
Installaon and Assembly Instrucons located in
the appendix of this manual.
 Rinnai recommends replacing the check valve
when replacing the water heater.
The Ubbink Polypropylene Translucent (PPTL for U.S. Applicaons) and/or Polypropylene S
(PPS for Canadian Applicaons)
CVent can be used on both the combuson air and exhaust. Field supplied PVC material
can only be used on the combuson air side and MUST NOT be used for the exhaust. For
Canadian installaon, all materials must be ULC-S636 approved.
WARNING

17 Rinnai CVent
Maximum Equivalent Vent Length
In the table below you nd the maximum equivalent pipe length of the exhaust and intake venng.
When determining equivalent exhaust and intake vent lengths add:
•6 feet for each 90° elbow
•3 feet for each 45° elbow
•Add any vent extension lengths which are added within the header
due to increased spacing of the water heaters
•Header kits have already been counted and do not need to be added.
*Approved exhaust and intake diameter is 8”.
Tankless Rack System (TRS) Venng Conguraon Summary (PPTL & PPS)
TRS Conguraon Minimum Equivalent
Vent Length (Ft)
Maximum Equivalent
Vent Length (Ft) Approved C-Vent Conguraon
Tankless Models
# of
Tankless
Units
Exhaust* Intake* Exhaust* Intake* Vent Opon Exhaust
Posion
C199i
(REU-KBD3237FFUDC-US)
8
One Elbow + Terminaon
Appliance
Adapter
41
Appliance
Adapter Room Air Conguraon
Vercal
Only
780
2 to 6 100
8
9
41 41 Parallel Pipe Conguraon
(Dierent Pressure Zone)
(Page 23)
780 80
2 to 6 100 100
C199i
(REU-KBD3237FFUDC-US);
RUC98i
(REU-KBD3237FFUD);
RU98i
(REU-KB3237FFUD-US)
8
15
41 41
Vercal or
Horizontal
Parallel Pipe Conguraon
(Same Pressure Zone &
Face the Same Direcon)
(Page 23)
2 to 7 100 100
Vercal Terminaon
There should be a minimum of 36” between exhaust and
intake terminaons.
CVent Terminaon Clearances
Clearances of Brackets
All supports such as wall brackets on the external
façade or spacer blocks in a shaft must be
assembled in a maximum distance of 78 in (2 m).
Where there is a bend, additional spacer blocks or
wall brackets can be planned before and after the
bend, depending on the local situation.
Freestanding Components
Components, which are assembled freestanding
vertical (roof termination) with a length of more than
59 in (1.5 m), must, depending on the amount of
wind and snow level expected, be additionally
secured to the building with guys or braces.
Vent termination per ANSI Z223.1/NFPA 54. For
clearances not specified in ANSI Z223.1/NFPA 54,
clearances are in accordance with local installation
codes and the requirements of the gas supplier.
12” OVER MAX.
SNOW LEVEL OR
24” WHICHEVER
IS GREATER
INTAKE - PVC
EXHAUST - PPTL/PPS
36” MINIMUM INSIDE
EDGE TO INSIDE EDGE

Rinnai CVent 18
CVent Terminaon Clearances
This appliance along with the CVent Common Vent System is cered with the Cvent 8-in Wall Terminaon Kit,
(790004) mounted in the orientaon shown below.
Horizontal Terminaon The exhaust and combustion air terminations must
follow these clearances:
[1] 12 inch minimum vertically from bottom of
combustion air termination to ground or anticipated
snow line.
[2] From edge of exhaust termination to edge of
combustion air termination:
Minimum of 36”
Maximum of 20’
[3] 36 inch minimum from multiple exhaust CVents
There should be a minimum of 36” between exhaust
terminations in multiple common vent installations.
The vent (exhaust & combustion air) terminations to be
as specified in table in "Maximum Equivalent Vent
Length" Section above (model specific).
NOTE: During colder weather when the exhaust temperature
is much hotter than the outside air, the exhaust
fumes condense producing water vapor. As a result
a plume of water vapor may be seen leaving the
exhaust.
MAXIMUM 20’
MINIMUM 36”
EXHAUST
VENT
COMBUSTION
AIR
VENT
Min 36”
Min 36”
Max 20’
Exhaust
Vent
INTAKE IS NOT
ALLOWED WITHIN THE
SHADED AREA
Combustion
Air Vent
Combustion
Air Vent
Combustion
Air Vent
Min 12” above grade or
anticipated snow level
Combustion
Air Vent
Combustion
Air Vent Min 36”

19 Rinnai CVent
Combuson Air Requirements (Commercial Applicaons with C199i Only)
Common Vent Applications Utilizing Room Air
Only the C199i (REU-KBD3237FFUDC-US) tankless water heater is certified to utilize room air in
commercial applications using Rinnai Common Vent System.
Common Vent Room Air
Appliance Adapter
Combustion Air Requirements
This rack system requires adequate combustion air for ventilation and dilution of flue gases. Failure to
provide adequate combustion air can result in unit failure, fire, explosion, serious bodily injury or death.
Use the following methods to ensure adequate combustion air is available for correct and safe
operation of this rack system.
Important: Combustion air must be free of corrosive chemicals. Do not provide combustion air from
corrosive environments. System failure due to corrosive air is not covered by warranty.
Combustion air must be free of acid forming chemical such as sulfur, fluorine and chlorine. These
chemicals have been found to cause rapid damage and decay and can become toxic when used as
combustion air in gas appliances. Such chemicals can be found in, but not limited to bleach, ammonia,
cat litter, aerosol sprays, cleaning solvents, varnish, paint and air fresheners. Do not store these
products or similar products in the vicinity of the water heater system.
Unconfined Space:
An unconfined space is defined in National Fuel Gas Code, ANSI Z223.1/NFPA 54 as “a space whose
volume is not less than 50 cubic feet per 1000 Btu/hr (4.8 m3 per kW per hour) of the aggregate input
rating of all appliances installed in that space. Rooms communicating directly with the space in which
the appliances are installed, through openings not furnished with doors, are considered a part of the
unconfined space.” If the “unconfined space” containing the system is in a building with tight
construction, additional outside air may be required for proper operation. Outside air openings should
be sized the same as for a confined space.
Confined Space:
(Small Room, Closet, Alcove, Utility Room, Etc.)
A confined space is defined in the National Fuel Gas Code, ANSI Z223.1/NFPA 54 as "a space whose
volume is less than 50 cubic feet per 1000 Btu/hr (4.8 m3 per kW per hour) of the aggregate input rating
of the combined appliances installed in that space." A confined space must have two combustion air
openings. Size the combustion air openings based on the BTU input for all gas utilization equipment in
the space and the method by which combustion air is supplied.

Rinnai CVent 20
Louvers and Grills
When sizing the permanent opening consideration
must be taken for the design of the louvers or grills
to maintain the required free area required for all
gas utilizing equipment in the space. If the free
area of the louver or grill design is not available,
assume wood louvers will have 25% free area and
metal louvers or grills will have 75% free area.
Under no circumstance should the louver, grill or
screen have openings smaller than 1/4”.
Example:
Wood: 10 in x 12 in x 0.25 = 30 in2
Metal: 10 in x 12 in x 0.75 = 90 in2
Location
To maintain proper circulation of combustion air
two permanent openings (one upper, one lower)
must be positioned in confined spaces. The upper
shall be within 12” of the top of the confined space
and the lower opening shall be within 12” of the
bottom of the confined space. Openings must be
positioned as to never be obstructed.
Using Outdoor Air For Combustion
Outdoor air can be provided to a confined space
through two permanent openings, one commenc-
ing within 12 in. (300mm) of the top and one
commencing within 12” (300mm) of the bottom, of
the confined space. The openings shall
communicate to the outside by one of two ways.
Exhaust
Vent termination per ANSI Z223.1/NFPA 54. For
clearances not specified in ANSI Z223.1/NFPA 54,
clearances are in accordance with local installation
codes and the requirements of the gas supplier.
(Be sure to also maintain 12” above grade or
anticipated snow level)
Combuson Air Requirements (Commercial Applicaons with C199i Only)