Rinnai Continuum Series User manual

Continuum and Integrity
REU2532-FFU and REU2532-FFU-C
Series Water Heaters
SERVICE MANUAL
Rinnai Corporation
103 International Drive
Peachtree City, Ga. 30269
Telephone number [phone]
No portion or part of this manual may be copied without prior permission from Rinnai Corporation.

REU-2532FFU Series 2Rinnai
Key to Warning Symbols
Failure to comply with the following instructions may results in serious personal injury or
damage to the appliance.
Be careful of possible electric shock. Wiring inside this appliance may potentially be at 120
volts.
Disconnect power supply to unit when carrying out the following service repairs.
Read Fault Diagnosis and Wiring Diagram carefully to avoid incorrect wiring.
Do not disassemble. Parts within can not be exchanged or diagnosed faulty.
Please follow instructions in chapters to ensure safe and appropriate service.
After completing the service and confirming that there are no water or gas leaks or incorrect wiring,
test operation of the appliance. After confirming normal operation, explain what was serviced to the
customer and the operating principles, if necessary.
The information in this manual was compiled by Rinnai Technical Services. While many individuals
have contributed to this publication, it will be successful only if you – the reader and customer – find
it useful. We would like to extend an invitation to users of this manual to make contact with us, as
your feedback and suggestions are valuable resources for us to include as improvements. Rinnai is
constantly working toward supplying improved appliances as well as information, and specifications
may be subject to alteration at any time.

REU-2532FFU Series 3Rinnai
Table of Contents
Glossary of Terms and Symbols .............................................................................................................. 4
1. Introduction .................................................................................................................................. 5
2. Features ......................................................................................................................................... 6
3. Dimensions .................................................................................................................................... 8
4. Installation .................................................................................................................................... 9
5. Remote Controls......................................................................................................................... 10
6. Safety Devices ............................................................................................................................. 12
7. Specification................................................................................................................................ 14
8. Cut-away Diagram ............................................................................................................... ..... 16
9. Schematic Diagram .................................................................................................................... 17
10. Combustion Specifications ........................................................................................................ 18
11. Dip Switch Positions................................................................................................................... 19
12. Water Flows ................................................................................................................................ 22
13. Main Components ...................................................................................................................... 24
14. Time Charts ................................................................................................................................ 26
15. Operation Flow Principle .......................................................................................................... 28
16. Operation Principles .................................................................................................................. 30
17. Error Messages........................................................................................................................... 32
18. Diagnostic Points ........................................................................................................................ 34
19. Wiring Diagram ......................................................................................................................... 35
20. Fault Diagnosis ........................................................................................................................... 36
21. Electrical Component Analysis ................................................................................................. 37
22. Gas Conversion........................................................................................................................... 47
23. Gas Pressure Setting Procedure................................................................................................ 52
24. Dismantling for Service ............................................................................................................. 54
25. Exploded Diagram ..................................................................................................................... 60
26. Parts List ..................................................................................................................................... 64

REU-2532FFU Series 4Rinnai
Glossary of Terms and Symbols
This glossary of terms and symbols is provided to assist you in understanding some of the
language used throughout this manual.
DB(A) - sound pressure level in decibels, “A” range
DC - direct current
AC - alternating current
WFCD - water flow control device
FB - feedback information
Hz. - hertz
IC - integrated circuit
BTU/H - British thermal units
PSI - Pounds per square inch
LED - light emitting diode
GPM - gallons per minute
mA - milliamps
W.C. - inches of water column
mm - millimeters
Nox - oxides of nitrogen NO & NO2
OHS - overheat switch
PCB - printed circuit board
CPU - central processing unit
POT - potentiometer
rpm - revolutions per minute
SV - solenoid valve
∅∅
∅∅
∅- diameter
∆∆
∆∆
∆°°
°°
°F - delta T or temperature rise above ambient
POV - modulating valve
TE - thermal efficiency
TH - thermistor
TIN - temperature of incoming water
Tout - temperature of outgoing water

REU-2532FFU Series 5Rinnai
1. Introduction
The brand name Continuum refers to “Endless Hot Water”. The new Continuum series has been
developed in response to the growing changes in the lifestyle of our customers, and the increasing
diversification and sophistication of demand in the marketplace.
The Continuum series offers reduced cost with advanced safety features, and an option to connect one,
two, or three remote temperature control pads. Residential units can use up to three optional keypads,
commercial units only allow one keypad per heater.
The Continuum REU-2532 series is delivered with the maximum hot water temperature output set at
120 °F without the remote control. When using controllers you can adjust your hot water output from 96
– 120 °F using the “BC” and “BSC” controllers. The “MC” control will allow water temperature
adjustments from 96 – 140 °F, and the “MCC” control used with the commercial unit, allows
adjustments from 96 - 180°F. .
About the Continuum
The front cover of each appliance in the new series is formed from 0.6 mm coated steel. Secured to the
main box assembly by (4) screws. Seals around the front cover prevent water from entering the
appliance.
Combustion air is drawn from outside the building, and combustion by-products discharge outside the
building through a coaxial flue system. The general layout of components is shown on page 16. All
components are supported within the box formed from 0.8 mm coated steel.
The heat exchanger occupies the top section of the casing, and the burner is situated in a chamber
formed from 0.8 mm aluminized steel, attached to the bottom of the heat exchanger. The copper tubing
material used in the heat exchanger consist of, Phosphorus Dioxide Copper, (C1220P). The material
used to solder the heat exchanger pipes is, Phosphorus Bronze Brazing, (main components are P, Ag,
and Cu) (JIS No. BcuP-2). None of these materials contain lead.
The air for combustion is supplied by a fan, which is connected to the burner box by a duct at the left
side of the appliance, directly under the burner.
Gas and water controls are situated at the bottom right of the appliance, directly under the manifold. The
“O”ring material on the water and gas connections are made from EPDM, (Ethylene Propylene Diene)
rubber.
The burner assembly is made up of (16) identical stainless steel Bunsen burners, secured by an
aluminized steel framework. Each burner is capable of handling up to 11,250 BTU’s. An aluminum
manifold with (32) integrally molded injectors supplies gas to the burners, and is attached to the front
lower cover of the burner box.

REU-2532FFU Series 6Rinnai
2. Features
Installation
The lightweight, slim, compact design enables ease of installation and improved appearance. The remote
controls (where fitted) are connected to the appliance by (2) core non-polar cable, or low voltage
thermostat wire, ensuring easy wiring and eliminating problems of mis-connections. Since the remotes
use a 12 VDC digital signal, there’s no-way you can cross up the wiring. You can connect the black
wires to black wires at one terminal, black and white at another, and still not short the units out.
Low Noise Level
Low noise level design enables these appliances to be installed in apartment units, townhouses, and
other high density residential areas with little concern about noise disturbances.
Safety
Various safety devices controlled by a micro- computer ensure complete safety. Also, the anti-frost
device automatically prevents the water inside the appliance from freezing by using small electrical
ceramic heaters, connected to the pipe-work at strategic locations throughout the appliance. The unit has
a secondary freeze prevention device that will allow the unit to fire for three seconds if the water
temperature inside the appliance drops below 37 °F. This mode will heat the water inside the unit back
up to 57 °F. The anti-frost devices should prevent the unit from freeze-ups down to the –30 °F, in a no
wind situation. This feature functions as long as the unit has power and gas.
Economy
Direct ignition to the main burner eliminates wasteful pilot gas consumption. The combustion fan rpm is
proportionally controlled with the gas consumption. This maintains high energy efficiency, as the gas
consumption changes with increased or decreased water flows. The unit’s thermal efficiency rating is;
0.87 for (LP) units and 0.82 for natural gas units.
Water Supply Control
The water supply capacity varies proportionally from 0.5 to 8.5 GPM’s. A suitable volume of hot water
can be supplied throughout all seasons by the water flow control device and water flow
servomechanism. The Continuum 2532 series will supply up to 6.5 GPM’s at a 50°F rise or up to 8.5
GPM’s at a 35 degree rise, controlled by an automatic electro-mechanical water control flow device.
Details pertaining to water flows can be found in the water flow charts in this manual.

REU-2532FFU Series 7Rinnai
Water Temperature Control
With an “MC” remote control connected, the hot water control range at the key pad is 96 – 140 °F. The
“BC” and “BSC” key pads allow for adjustments between 96 – 120 °F. The “MCC” key pad allows the
commercial unit to be adjusted from 96 – 180 ° F. This allows the Continuum to be set to comply with
various State codes pertaining to maximum water temperatures allowed for homes, child care centers,
elderly care centers, etc. where the water temperature can not exceed a certain set point.
Over Temperature Control
All Continuum models incorporate a device to prevent the hot water temperature from exceeding the
pre-set temperature by more than 4 °F.
Temperature Locks
With the remote control(s) connected, the pre-set water temperature can only be altered between 96 –
110 °F while water is flowing. Also, if the remote control circuit fails while water is flowing, the unit
defaults back to 100 °F. That prevents inadvertently increasing the temperature to a hazardous level
while someone is in the shower. This is an Anti-Scald feature.

REU-2532FFU Series 8Rinnai
3. Dimensions

REU-2532FFU Series 9Rinnai
4. Installation
Piping recommendation.

REU-2532FFU Series 10 Rinnai
5. Remote Controls
The MC45-4US, BC45-4US, BSC45-4US , and the MCC45-4US remote key pads were specifically designed
for use with the Continuum water heaters.
Features include:
Color coordination to allow immediate recognition of the temperature “hot” and “cold” buttons.
Large LED display. Temperature adjustments in two degree increments from 96 – 110 °F, then two five
degree increments from 110 – 115 °F , and 115 °F - 120 °F , on the BC, BSC and MC controllers.
The “MC” controller has two additional ten degree increments, from 120 to 130, and 130 to 140 °F.
The BC, BSC and MC controls are for domestic use. The MCC control allows the temperature to be adjusted
from 96°F - 180°F , this control is used only for commercial units.
Water temperature adjustment only in the range of 96 – 110 °F while hot water is flowing. Anti-Scald feature
defaults unit back to 100 °F, if remote fails or becomes disconnected while water is flowing.
Enhanced communication system between the remote controls, allowing priority temperature selection from
each remote control.
Remote controls offer self-diagnostics in the event of a fault with the unit, simplifying service calls. To
retrive the last ten error codes press and hold the green button down, while holding this button down press the
red button. This will gi ve you a fault code history. To reset, turn the power supply off to the unit , then
reapply power.
Flashes “LC” in the event of a liming condition. To reset the “LC” mode, power must be turned off to the
unit and then reapplied.
 To measure the flow rate through the unit using the remote control, press the red button and hold it
down while the unit is operational, while holding the red button down press the green button. This
will give you the gallons per minute flowing through the heater.
 To measure the water heater’s output water temperature press the blue button and hold it
down while the unit is operational, while holding the blue button down press the green button. This
will give you the water temperature being delivered by the unit.

REU-2532FFU Series 11 Rinnai
6. Suggested Connection Methods for Remotes
There must be at least one cable from the remote control(s) connected to the Continuum water heater.
Power for the remote(s) is supplied from the PC board. On the front of the PCB, there are two screws
labeled terminals for controls. This is the 12VDC digital power supply for the remotes. Use low voltage
thermostat wire when wiring up the keypads.

REU-2532FFU Series 12 Rinnai
7. Safety Devices
Flame Failure
Situated to the right of the burner in the front of the combustion chamber, the flame rod monitors the
combustion process. This sensor monitors the flame intensity, while the PCB compares this signal to the
feed back signal from the combustion fan motor, water flow control, and gas flow through the POV
valve. If any one of the feedback signals are incorrect, the unit will shut off, preventing discharge of
gas to the burner.
Over Heat Protection Device
Also referred to as an Over Heat Switch. This device is fitted to a bend section at the inlet to the heat
exchanger. If the flame remains on to the burner after the tap is closed and the water temperature inside
the heat exchanger reaches 194 ° F, a 12 volt DC bi-metal cut-off switch will shut off the gas supply to
the solenoids.
No Water
Should the incoming water flow become restricted or stop, the water flow sensor will cease to send a
magnetic pulse signal to the PCB, in turn preventing gas to flow into the combustion chamber. If you
have restricted flow, first check to ensure the inline water filter is not clogged up.
Thermal Fuse
Wrapped around the entire surface of the heat exchanger you will find a thermal fuse. This device
activates in the event the heat exchanger burns out, or the temperature outside the heat exchanger
reaches 264 °F. If the thermal fuse melts, it breaks an electronic circuit which in turn shuts off the
power supply to the gas solenoids, shutting the unit off.
Combustion Fan Revolution Check
The combustion fan rpm’s are continually monitored by a magnetic pulse generator connected to the
PCB. If the fan revolutions deviate from the speed required for complete combustion, a signal is sent to
the PCB and the revolutions adjust accordingly. (If not the unit shuts down)
Automatic Frost Protection
When the temperature inside the appliance drops below 37 °F , the frost sensing device inside the
appliance activates the anti-frost heaters to prevent the water inside the unit from freezing. The anti-
frost heaters remain ON until the temperature inside the appliance rises to 57 °F. There are four (16)
watt anti-frost heaters located at various points throughout the main water flow area of the appliance.
The unit also incorporates the ability to fire for (3) seconds in the event the anti-frost heaters can not
keep the water temperature from dropping below 37 °F. This unique feature will heat the water in the
lines inside the appliance back up to 57 °F. Both of the above features function as long as the unit has
power and gas. There is an optional freeze protection system that can be added to the unit’s piping.
Contact your supplier for a diagram if you want to install an auto drain down kit on your unit.

REU-2532FFU Series 13 Rinnai
5 °F Over temperature Cut-Off
The temperature of the outgoing hot water is constantly monitored by the water temperature thermistor
located near the outlet of the appliance. If the outgoing water temperature reaches 5 °F above the preset
temperature, the burner will automatically go out. The burner will only ignite again once the outgoing
hot water temperature falls below the preset temperature.

REU-2532FFU Series 14 Rinnai
8. SPECIFICATIONS
Rinnai model number REU-V2532FFU-US REU-V2532FFU(C)-US
Type of appliance Temperature controlled continuous flow gas hot water system
Operation With / without remote controls, mounted in kitchen, bathroom, etc.
Exhaust system Direct Vent - Forced combustion
Maximum/Minimum gas rate (Input BTU's) 180,000 BTU's - 15,000 BTU's Natural Gas
180,000 BTU's - 15,000 BTU's Propane Gas
Hot water capacity, (50°F rise) 0.5 to 6.5 GPM
Maximum hot water capacity, (35°F rise) 8.4 GPM
Setpoint Temperature (without remote) Factory setting - 120°F Factory setting - 140°F
Temperature range (with remote) MC controller : 96 - 140°F BC controller : 96 - 120°F
BSC controller : 96 - 120°F MCC controller : 96 - 180°F
Approved gas type Natural or Propane - Ensure unit matches gas type it's being installed on.
Installation Indoor Only
Dimensions Height 23 5/8" Width 13 25/32"
Depth 8 13/16"
Weight 49 Lbs.
Thermo Efficiency rating 0.87 (Propane) 0.82 (Natural)
Noise level 49 dB (A)
Connections Gas supply 3/4" MNPT Cold water inlet 3/4" MNPT
Hot water outlet 3/4" MNPT
Ignition system Direct electronic ignition
Electrical consumption Normal 75 watts Standby 5.5 watts
Anti-frost protection 100 watts
Water temperature control Simulation feedforward and feedback.
Water flow control Water flow sensor, electronic water control device, and electronic by-pass control
device
Recommended Minimum water
supplypressure 20 PSI (Rinnai recommends 50-80 PSI for maximum performance)
Maximum water supply pressure 150 PSI

REU-2532FFU Series 15 Rinnai
Safety devices
Appliance - AC 120 Volts - 60Hz.
Remote control DC 12 Volts (Digital)
Flame failure - Flame rod
Boiling protection- 203°F
Remaining flame (OHS) 194°F bi-metal switch
Thermal fuse 264°F
Automatic frost protection - Bi metal sensor & anti-frost heaters
Combustion fan rpm check - Integrated circuit
Over current - Glass fuse (3 amp)
If remote fails or becomes disconnected unit defaults to 100°F with water
flowing, this is an anti-scald feature.
Remote control cable Non-polarized two core cable or low voltage thermostat wire
Clearances from combustibles
Top of heater 6"
Front of heater 6"
Sides of heater 2"
Back of heater 0"
Floor 12"
Vent/Air Intake 0"
Minimum and Maximum gas supplypressure Natural Gas : *Minimum 6" W. C.
(NAT.) **Maximum 10.5" W. C. Propane Gas: *Minimum 10" W. C. (LPG) **Maximum14" W. C.
Manifold Gas Pressure Natural Gas 3.7" W. C. high fire 0.77" W. C. low fire
LPG: 4.2" W. C. high fire 0.93" W. C. low fire
Warranty 2532FFU: Ten years heat exchanger / five years parts (see unit's warranty for details)
2532FFU(C): Five years heat exchanger and parts (see unit's warranty for details)
*Minimum input pressure is for the purpose of input adjustments.
**Do not exceed maximum pressure.

REU-2532FFU Series 16 Rinnai
9. Cut-way Diagram
REU-2532-FFU Series

REU-2532FFU Series 17 Rinnai
10. Schematic Diagram
REU-2532-FFU Series

REU-2532FFU Series 18 Rinnai
11.
Combustion Specifications
Model: REU-2532-FFU
Item
Gas type Natural Propane
Minimum Btu’s 15,000 15,000
Gas consumption
Maximum Btu’s 180,000 180,000
Upper ∅0.95 ∅0.75Injector Diameter Lower ∅1.6 ∅1.15
Main Burner B3A7-1
(Lean and Rich Bunsen Burner)
Main Damper
H73-115 Upper: ∅6, Lower: (Not used)
Minimum supply 6” W.C 10” W.C
Maximum supply 10.5” W.C 14” W.C
Gas Pressure
Supply/Manifold
Minimum manifold 0.77” W.C 0.93” W.C

REU-2532FFU Series 19 Rinnai
12. DIP SWITCHES
Contact Rinnai for dip switch settings when changing PC board or setting up unit for special applications. Failure to set dip
switches to the proper position will result in damage to the unit, property damage, personal injury or death. DO NOT,
adjust dip switches unless you have written permission from Rinnai. Call 1(800)621-9419 to set-up a special training class
pertaining to dip switch functions.
The dip switches on this appliance can be adjusted to deliver water temperatures from 108°F - 180°F, only for commercial
type applications, and to check/reset low/high fire manifold pressures, and to set the unit up to operate on a different gas
type in the event the unit was converted from one gas type to another. In residential applications these switches should
never be readjusted from the factory setting. The factory default temperature setting is 120°F.
The set-up configuration for the water heater differs depending on:
Gas type
Maximum water flow selected
Temperature limiting requirements
Application type
“SW1” row of switches
1. Short or long flue
2. Fixed water temperature with or without remote.
3. To select a desired water temperature for commercial applications
4. To select a desired water temperature for commercial applications
5. To select a desired water temperature for commercial applications
6. Flow switch activated or de-activated.
7. Combustion control (Forced low fire).
8. Combustion control (Forced high fire).
Combustion control switches are used to set or check the manifold gas pressures on this appliance. When dip
switch #7 is placed in the “ON” position, it places the appliance into forced low fire. When dip switches #7 and
#8 are placed in the “ON” position, it places the unit into forced high fire. Before placing the unit into forced
low or high fire, you MUST ensure you have maximum water flow through the appliance. Open several
faucets throughout the residence before proceeding.After checking or setting manifold gas pressures, dip
switches 7 and 8 MUST be placed in the “OFF” position, to return the appliance to a normal operating
mode. Failure to place these switches to the “OFF” position will cause the unit to mal-function.
The REU-2532 series water heaters comes from the factory set to deliver a water temperature of 120 °F, the REU-2532-C
series is set to deliver 140°F. However, the commercial series will allow water temperature adjustments up to 180°F for
applications such as; hotels, car washes, laundry mats, hospitals, farms, processing plants, etc., that require water
temperatures above 120°F. Temperatures above 120 °F are not recommended due to burn hazards. Please use extreme
caution if adjusting water temperatures above 120 °F.
Explanation of “SW1” Dip Switches;
(Switch #1) Short or Long Flue Switch; at “SW1” row of switches, should be placed in the “ON” position for vent
lengths not exceeding twenty-one equivalent feet. For vent lengths over twenty-one equivalent feet this switch should be
placed in the “OFF” position.
(Switch #2) Fixed Water Temperature With or Without Remote. When this switch is set to the “OFF” position,
switches 3 – 6 can be adjusted to a pre-determined position that will not allow the remote pad to be adjusted above a
selected temperature. When set to the “ON” position and no keypad is being used, the unit can be set to deliver a set
temperature from 108, 120, 130, etc. DO NOT make adjustments without written permission from Rinnai.

REU-2532FFU Series 20 Rinnai
(Switches 3,4, & 5) Temperature Adjustment Switches. Switches #3, 4, and 5 are used to set fixed temperatures with or
without the remote keypads. Contact Rinnai for dip switch settings when changing the unit’s PC board or setting up special
applications. Failure to set dip switches to the proper position will result in damage to the unit, property damage, personal
injury or death. DO NOT, adjust switches unless you have written permission directly from Rinnai. Call 1(800)621-9419 to
set-up a special training class pertaining to dip switch functions.
(Switch #6) Flow Switch and Temperature Adjustments. Rinnai offers a flow switch that can serve as an anti-scald
device. This switch is installed in-line with each bathroom. Therefore, if someone was using water above 120°F and a tap
was turned on in one of the bathrooms, the unit would automatically default back to 120°F to prevent scalding. When dip
switch #6 is set to the “ON” position this function is activated. At the present time this switch is not used in the U.S.
market, due to anti-scald devices and/or pressure balancing valves presently being used in our market.
(Switches 7& 8) Low/High Fire Combustion Control Switches. Dip switch # 7 is used to place the unit into forced low
fire when checking and/or setting manifold gas pressures. Dip switch #7 and #8 are used to place the appliance into forced
high fire. Before making any adjustments to these switches, please ensure you follow the gas pressure setting procedure
found in this manual.
“SW2” row of Dip Switches
1. Gas type (Used only when replacing PCB or converting unit)
2. Lime control switch activated or de-activated.
3. Plus three degrees or plus six degrees differential.
4. Type of unit. (Residential or commercial)
(SW2) Explanation of “SW2” row of Dip Switches
(Switch #1) Gas Type Switch. When set to the “OFF” position the unit is setup to operate on propane gas, in the “ON”
position it is setup for natural gas.
(Switch #2) Lime Control Switch. Set dip switch #2 to the “OFF” position to activate the lime control function. To
deactivate this function place this switch in the “ON” position.
(#3) Temperature Differential Switch. The temperature of the outgoing water is constantly monitored by the outlet
temperature thermistor. If the outlet water temperature rises to more than 5.4°F above the preset temperature, the burner
will automatically go out when dip switch #3 is in the “OFF” position. The burner will ignite again once the outlet water
temperature falls below the preset temperature. If this switch is set to the “ON” position it will allow a 10.8 °F rise.
(Switch #4) Type of Unit. Danger; do not adjust this dip switch. Adjusting this switch will result in damage to the unit,
property damage, personal injury, or death.