Rinnai Continuum Series User manual

RINNAI
Continuum
Water Heater Model
REU-2424-W and REU-2424-C
General Use
Rinnai Corporation
103 International Drive
Peachtree City, Ga. 30269
Telephone number [phone]

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No portion or part of this manual may be copied without prior permission from Rinnai Corporation.
Key to Warning Symbols
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.
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 disassembly. Parts within can not be exchanged or diagnosed faulty.

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Table of Contents
Glossary of Terms and Symbols …………………………………………………………………….. 3
1. Introduction ………………………………………………………………………………….. 4
2. Features ………………………………………………………………………………….. 5
3. Dimensions …………………………………………………………………………………. 7
4. Installation ………………………………………………………………………………… 8
5. Remote Controls ……………………………………………………………………………. 9
6. Safety Devices ……………………………………………………………………………….. 10
7. Specification ………………………………………………………………………………… 13
8. Cut-away Diagram ………………………………………………………………………….. 14
9. Schematic Diagram ………………………………………………………………………… 15
10. Combustion Specifications …………………………………………………………………. 16
11. Water Flows …………………………………………………………………………………. 17
12. Main Components……………………………………………………………………………. 19
13. Time Charts ………………………………………………………………………………….. 21
14. Operation Flow Principle …………………………………………………………………… 22
15. Operation Principles ………………………………………………………………………… 24
16. Error Messages ……………………………………………………………………………… 26
17. Diagnostic Points ……………………………………………………………………………. 27
18. Wiring Diagram …………………………………………………………………………….. 28
19. Fault Diagnosis ……………………………………………………………………………… 30
20. Electrical Component Analysis ……………………………………………………………. 39
21. Gas Pressure Setting Procedure …………………………………………………………… 44
22. Dismantling for Service ……………………………………………………………………. 46
23. Exploded Diagram ………………………………………………………………………….. 52
24. Parts List …………………………………………………………………………………….. 56

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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

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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.
The Continuum model REU2424-W is delivered with the maximum hot water temperature output set at
120 °F without the remote control. The REU2424-C is delivered set at 140°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 and the flue outlet prevent water from
entering the appliance.
Air inlets are situated in the front panel of the 2424 external unit. Air passes through the inlets and is drawn
into the combustion chamber at the rear of the fan housing. The by-products of combustion on the external
unit are expelled from the appliance through a flue outlet situated on the front of the appliance, at the top.
The general layout of components can be seen in the cut-away diagram, see table of contents for page
number. All components are supported within the unit’s casing, which is made 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 (18) identical stainless steel Bunsen burners, secured by an aluminized
steel framework. Each burner is capable of handling up to 10,000 BTU’s. An aluminum manifold with
(18) integrally molded injectors supplies gas to the burners, and is attached to the front lower cover of the
burner box.

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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, 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 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
Varies safety devices controlled by a micro- computer ensure complete safety. Also, the anti-frost device
(where fitted), 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 prevent 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 the –30 °F, in a no wind situation.
This feature functions as long as the unit has power. See optional freeze protection in the owner’s manual
for power failure protection.
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 AFUE rating is 82%.
Water Supply Control
The water supply capacity varies proportionally from 0.6 to 6.5 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 2424 and 2402 models will supply up to 6.5 GPM’s, 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.

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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 140 – 180 °F. The “MCC” key pad can be configured to deliver water
temperatures from 96 - 140°F in low temperature applications. Contact Rinnai for details when using the
commercial unit in temperature applications below 140°F . This allows the Continuum to be set to comply
with various State codes pertaining to temperature control in homes, child care centers, and elderly care
centers were the temperature can not excess 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. This prevents inadvertently increasing the temperature to a hazardous level, while someone
is in the shower. This is an Anti-Scald feature.

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3. Dimensions
Note: All dimensions are in inches.

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4. Installation
Recommended piping. .

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5. Remote Controls
The MC45-3US, BC45-3US, BSC45-3US , and the MCC45-3US 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 – 116 °F, then one four degree increment from 116 –
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 on the REU-2424C commercial unit.
•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 at each
remote control.
•The remote offers self-diagnostics in the event of a fault with the unit, simplifying service calls.
•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.