Rinnai REU-24 W-A User manual

CONTENTS
DEVELOPMENT BACKGROUND.....................................
CHARACTERISTICS ..............................................
INTRODUCTION.................................................
SAFETY DEVICES ..............................................
GLOSSARY of ABBREVIATIONS.....................................
SPECIFICATION.................................................
COMBUSTION SPECIFICATION
......................................
DIMENSIONS...................................................
CUT-AWAY DIAGRAM...........................................
FEEDFORWARD
WATER FLOWS
GAS RATE
. . .
AND FEEDBACK..................................
.................................................
.................................................
DEFAULT TEMPERATURE SETTING.................................
GAS AND WATER CONTROLS......................................
OPERATION....................................................
OPERATIONAL FLOW CHART
.....................................
TIMJ3 CHART..................................................
FAULT FINDING PROCEDURE.....................................
GAS PRESSURE SETTING PROCEDURE ...............................
COMFONENT ANALYSIS..........................................
BLOCK DIAGRAM...............................................
DIAGNOSTIC POINTS .............................................
WIRING DIAGRAM ..............................................
DISMANTLING FOR SERVICE
.....................................
SHOWERING TEMPEIbiTURES ......................................
PARTS LIST...................................................
EXPLODED DIAGRAM...........................................
SERVICE CONTACT POINTS .......................................
1
1
2
3
4
5
6
7
8
9
10
13
14
15
19
20
21
23
34
35
38
39
40
41
55
57
62
69

DEVELOPMENT BACKGROUND
The REU-24 W-A is one of a range of continuous flow water heaters produced by Rinnai. The main
features of this unit are: compact size, low NO, combustion, high efficiency, and remote temperature
control. Rimrai’s
patented ‘DECS’ combustion system has allowed for the volume of the heat
exchanger to be reduced by 75% compared with conventional instantaneous water heaters.
CHARACTERISTICS
Low Noise
Incorporation of the 49 dB(A) low noise design in the Infinity 24 allows for installation in crowded
or high density residential areas.
Convenience
Wide proportional temperature control of the hot water from 2.2 to 21 litres per minute, ensures hot
water at a suitable temperature throughout all seasons is selectable. Control of the water temperature
while on the rise to a particular preset temperature with the feedforward and feedback control system
prevents overheated water being supplied if the water heater is turned ON and OFF repeatedly.
The water temperature can be selected in 16 steps from 35°C to 75°C. The temperatures are 35-37-
38-39-40-41-42-43-44-45-46-48-50-55-60-75°C. As a result of the adoption of the electronic water
flow control device; the unit can be used in areas with low water pressure.
Installation
The
light weight, slim, compact form allows improved installation. The main unit and controls are
connected by 2 non-polar cables eliminating problems of mis-connection. Cable installation is simple.
’
Safety
In the event of a malfunction, one or more of the various safety devices will operate. Depending on
the fault, the Infinity 24 will be shut down by the P.C.B. or directly by the safety devices. In winter,
the automatically operated anti-frost protection heaters ensure that the water in the appliance does not
freeze up.
Economy
Direct ignition to the main burner eliminates wasteful pilot gas consumption. The air gas ratio is
always controlled to the most suitable level by the P.C.B., and as the water flow and gas consumption
changes, combustion conditions are controlled, maintaining high efficiency.
Conventional water heaters supply water at high temperatures. This means that the
pipework in the
house is also very hot. Hot pipes lose more heat than cooler pipes. With the Infinity 24, the water in
the house pipes can be kept much cooler, reducing heat loss and thus effectively saving energy.

INTRODUCTION
The front cover of the appliance is formed from 0.6 mm coated steel, secured to the main
box assembly by 4 (four) screws. Seals around the front cover and flue outlet prevent water
from entering the appliance.
Air inlets are situated in the rear of the main box. The general layout of components is shown
on the cut-away diagram on page 8. All components are supported within a box formed from
0.8 mm coated steel.
The heat exchanger occupies the top section of the box, and the burner is attached directly
to the heat exchanger.
The air for combustion is supplied by a fan which is connected directly to the burner
assembly.
Gas and water controls are situated at the bottom right of the appliance, directly under the
manifold. The products of combustion are expelled from the appliance through a stainless
steel nozzle situated on the front of the appliance, at the top.
The burner body is diecast aluminium, and the ports are formed
plaque. A two chamber manifold supplies gas to the burner. Two
in the inlet of the manifold.
in a ceramic [Cordierite]
brass orifices are situated
There are three thermistors - one fitted within the electronic water flow control device,
checking the incoming water temperature - part of the feedforward information; another fitted
to the outlet of the heat exchanger, checking the temperature of the water as it leaves the heat
exchanger; and a third situated at the outlet of the unit, checking the outgoing water
temperature. The Infinity 24 relies on feedforward and feedback information to operate
effectively. See page 9 for further explaination about how this control function operates.
The aim of this manual is to provide an operational reference specifically concerning the
Infinity REU-24 W-A water heater. A glossary of abbreviations is provided on page 4, to
assist you in understanding some of the language used throughout this manual. Further
information about this product is contained in the customers operation information booklet.

SAFETY DEVICES
Flame Failure
Situated on both sides of the burner, the flame rods monitor normal combustion, preventing any
discharge of gas to the burner if there is no flame and in conjunction with the P.C.B., isolate the gas.
Remaining Flame Safety Device
If the flame remains on the burner after the tap is closed, and the water temperature inside the heat
exchanger reaches 2OO“C, a DC 90 volt bi-metal cut-off switch isolates the gas to the solenoids.
Boiling Protection
The
heat exchanger outlet water temperature thermistor continually monitors the temperature of the
water flowing from the heat exchanger. Should the temperature of the water at this point reach
105°C
then a signal will be sent to the P.C.B. to shut off the solenoids and isolate the gas.
No Water
Should the incoming water flow become restricted or stop, then the water flow sensor will cease to
send a magnetic pulse signal to the P.C.B., in turn isolating the flow of gas to the burner.
Fusible Link
Is located on the internal rear of the casing. If the heat exchanger bums out, or the temperature
outside it reaches 152T, this device isolates the gas supply, and shuts down the unit completely.
Pressure Relief Valve
Located on the hot water outlet, this spring and valve seating type valve will, if the pressure inside
the heat exchanger reaches 1400 kPa, release the built up pressure until 1000 kPa is maintained.
Combustion Fan Revolution Check
The combustion fan rpm are continually monitored by a magnetic pulse counter connected to the
P.C.B. If the fan revolutions deviate from the speed required for complete combustion, a signal is sent
to the P.C.B. and the revolutions adjusted accordingly.
Automatic Frost Protection
When the outdoor temperature drops below 3.5T, the frost sensing device is activated, and the anti-
frost heaters prevent the water in the appliance from freezing. These anti-frost heaters remain ON until
the outdoor temperature rises to 11
.S’C. There are 5 anti-frost heaters located at various points in the
appliance. The anti-frost protection device will prevent freezing down to -20°C in a no wind situation,
and -15°C in a windy situation.
Water Bypass Distributor
Water at 60°C from the heat exchanger is mixed with cold water via the bypass system when the
preset temperature selected at the remote controls is less than 60°C.
Thermocouple
A thermocouple situated on the right hand side of the burner continually monitors combustion by
checking the tile temperature. Information is fed back to the P.C.B., which adjusts the air/gas ratio
if necessary.

GLOSSARY of ABBREVIATIONS
This glossary of terms is provided to assist you in understanding some of the language used
throughout this manual.
dB(A) -
DC -
DECS -
EWFCD -
FB -
FF -
Hz -
IC -
kcal/h -
kPa -
L/min -
LED -
mA -
MI/h -
mm -
mmH,O -
NO, -
OHS -
P.C.B. -
POT -
rpm -
sv -
TE -
TIN -
TOUT -
sound pressure level in decibels, “A” range.
direct current.
direct exchange combustion system.
electronic water flow control device.
feedback information.
feedforward information.
Hertz.
integrated circuit.
kilocalorie per hour.
kilopascals.
Litres per minute.
light emiting diode.
milliamps.
megajoule per hour.
millimetres.
millimetters of water (Gauge pressure).
oxides of nitrogen (NO & NO&
over heat switch.
printed circuit board.
potentiometer.
revolutions per minute.
solenoid valve.
thermal efficiency.
temperature of incoming water.
temperature of outgoing water.

SPECIFICATION
Type of appliance
Exhaust system
Rinnai Australia model N“
Installation
Operation
Dimensions
Temperature controlled continuous gas hot water system.
Forced combustion.
REU-24W-A
Externally mounted.
Remote control, mounted in kitchen and/or bathroom.
Width - 370 mm.
Height - 538 mm.
Death -
210 mm. I With bracket and flue extension ]
Weight
20 kilograms.
I
I
Connections
Ignition system
Gas consumption
Electrical consumption
Hot water capacity
Temperature range
Water flow control
Minimum operating pressure
Normal operating pressure
Minimum operating water flow
Power supply
Safety devices
Gas supply
- R W l2OA.
Cold water supply
-
R % l20A.
Hot water supply
-
R 3k l20A.
Direct electronic ignition.
Natural gas
- 185 MI/hHI, 21 Ml/h LOW.
Normal
- 72 Watts.
Standby
- 8 Watts.
Automatic frost protection
- 144Watts.
2.2 to 24
L/min. [ Raised 25°C ]
35°C to 75°C in 16 steps.
Electronic water flow control device.
15 kPa.
70 to 830 kPa.
2.5 L/min.
Appliance
-2301240 Volts 50 I-Ix.
Remote control
- DC 12 Volts Digital.
Flame failure
- Flame rod.
Remaining flame [OHS]
-200°C
bi-metal switch.
Boiling protection
- 105°C lockout thermistor.
Fusible link
- 152°C thermal fuse.
Burner light back
_
135°C bi-metal switch.
Pressure relief valve
-
Gpens - 1400 kPa.
-
Closes - 1000 kPa.
Automatic frost protection -
Bi-metal sensor & anti-frost heaters.
Combustion fan rpm check -
Integrated circuit system.
I

COMBUSTION SPECIFICATION
The FUXJ-24 W-A is only approved for use on Natural gas.
Consumption Input Orifice A Orifice B Gas type selection switch positions *
P=W FzThl
[=I
b4
4WOo
185 05.0 05.2
1 2
3 4 5
OFF ON OFF OFF OFF
* Down position = ON, Up position =OFF. See page 34 for further details.
Test Point Pressure Modulating valve
Fanspeed
Fpal
current [mA]
HZ
Maximum
0.70
158 f 5
128 f 2
Minimum
0.04
55 f 5
67.5 f 2
I
I I I
4
SCHEMATIC DIAGRAM
THERMAL FUSE
REMAINING FLAME
SAFETY DEVICE
ELECTRODE
FLAME ROD,
SPARK GENERATOR-
HEAT EXCHANGER
THERMISTOR (OHS)-
REV COUNTER-
ANTI-FROST
/ PROTECTION HEATER
HEAT EXCHANGER
ELECTRODE
AIR GAS RATIO
THERMOCOUPLE
COMBUSTION FAN
BY-PASS CONTROL
DISTRIBUTOR -
PRESSURE RELIEF
VALVE
\
MODULATING
SOLENOID
SOLENOID VAL
CHANGE-OVER
SOLENOID
i
I
c__.
;
7
ELECTRICAL
CONNECTION
4
HOT WATER SUPPLY
OUTLET THERMISTOR
VE
ELECTRONIC WATER FLOW
CONTROL DEVICE
-WATER FILTER
REMOTE CONTROL
HOT WATER OUTLET
GAS SUPPLY
U
CONNECTION WATER INLET
CONNECTION

FEEDFORWARD AND FEEDBACK
Feedforward Information
This is the information which the water heater uses to calculate the required parameters to give the
temperature selected on the remote control.
The data used is
a) Incoming water temperature
b) Water flow
c) Selected temperature at the remote control
This data is continually monitored by the P.C.B. and adjustments are made to maintain the
temperature selected on the remote control.
Feedback Information
This information is provided by the outgoing water temperature thermistor. The P.C.B checks the
temperature selected on the remote control against the temperature indicated by the outgoing water
temperature thermistor, and makes adjustments to the gas rate or water flow as required to maintain
the temperature selected on the remote control.
The temperature of the water discharged from the heat exchanger is maintained above
60°C. This is
to prevent condensation inside the heat exchanger. A thermistor located near the heat exchanger
monitors the water temperature.
The schematic diagram below indicates those components which are incorporated into the feedforward
and feedback system.
By-pass connection 1
I
P.C.B.

WATER FLOWS
With the Infinity 24, the maximum water flow possible without mixing at the tap is 21 litres a minute.
A simple calculation of the water flow rate in litres per minute can be made using the following
charts. The charts indicate the water flow from the Infinity 24 at various combinations of incoming
water temperatures, and the selected temperature at the remote control.
The vertical plane indicates the selected temperature at the remote, and the horizontal plane indicates
the flow of water in litres per minute. Remote control range is between
35°C and 75T, therefore the
water flow charts only show the temperatures in that range. The temperature rise is the difference
between the temperature of the incoming water and the selected temperature at the remote controls.
Select the appropriate chart depending on the incoming water temperature. Draw a horizontal line
across the graph from the selected temperature at the remote until it intersects the curve. At this point
draw the line in the vertical direction. The water flow is indicated where the line intersects the bottom
of the chart.
The chart below is a composite graph showing the water flows from the Infinity 24 at three different
incoming water temperatures. Graphs on the next page show the same information in separate formats.
TEMPERATURE RISE
1 deg 1
\
\
70-
60-
50-
40-
30-
20-
IO-
\
\
\
\
\
I
.IMIT
--__
I
0
I 1 <
510
15 20 21
VOLUME OF HOT WATER SUPPLY (LITRE.MIN)
INCOMING WATER SUPPLY 'C
T
Output water Incoming Incoming Incoming Incoming Incoming Incoming
temperature
+ 15°C
+ 25°C
+3oT
+ 35°C + 45°C + 55°C
Output water * 40 * 24
20 17.1 13.3 10.9
volume (L/min)
WW
Cwmh) (L/min)
(L/mid
(L/nU
* Calculated value of water capacity using mixing valve, at point of use.

16 18 ,20 22 24
The chart opposite indicates
that the water flow rate of
the Infinity 24 will, at a
preset temperature of 50°C
and an incoming water
temperature of X, be 13
litres a minute.
lj.5
Water flow (L/min)
The chart opposite indicates
that the water flow rate of
the Infinity 24 will, at a
preset temperature of 50°C
and an incoming water
temperature of WC, be 17
litres a minute.
Water flow (Llmin)
The chart opposite indicates
that the water flow rate of
the Infinity 24 will, at a
preset temperature of 50°C
and an incoming water
temperature of 25”C, be 24
litres a minute by mixing at
the tap, 21 litres a minute
without mixing.
214 6 8 10 12 14. 16 18 29
1 22 .2f
2.5
21
_.
Water flow (L/mid

Calculating The Water Flow
The following information is an outline of the formula required to measure accurately the flow rate
in litres per minute, as well as being the base for the charts on the preceding page. The most useful
way in which this formula can be utilised, is to calculate the water flow rate where there is maximum
gas input of 185MI/h.
Formula: INxTE
=(Tout - Tin) x 60 x Q
Where: Tin
=
Incoming water temperature.
Tout =
Outgoing water temperature as selected at the remote.
IN
=
Gas input!.
TE
=
Thermal efficiency*.
Q
=
Water flow in litres per minute.
# This is the maximum gas input converted from lvI.I/h into kilocalories. As 1 kilocalorie raises the
temperature of 1 litre of water by 1 degree centigrade, the method of calculation is to multiply the
input in MI/h by 239.
* Thermal efficiency may be in the range of 78% to 90%) depending on the temperature rise and
water flow. For the purpose of the following calculation we have assumed an efficiency of 80%.
Example data
Tin = 15°C
Tout = 60°C
IN = 44200 k&/h
TE = 80%
Q
= Water flow in
litres
per minute
Calculation
44200 x 0.8 = ( 60 - 15 ) x 60 x Q
35360
=45 x 60 x Q
35360 = 60xQ
45
786
= 6OxQ
78$
= Q
60
13.1 L/min

GAS RATE
The most common unit used to calculate the energy required to heat water is the kilocalorie.
If the full gas rate is not required to provide the required water temperature rise, [ie - when the
temperature selected at the remote controls is lower, or the incoming water temperature is higher 1;
the amount of gas that the water heater is going to use to carry out a specific heating task will change
proportionally to these variables. The actual gas rate is based upon the following calculation.
Calculating The Gas Input
Formula: (Tout - Tin) x 0 x 60 =IN
MI/h
239 x TE
See the previous page for an explanation of Tin, Tout, IN, TE and Q.
Example data Calculation
Tin = 15°C (60 - 15) x 10 x 60 = IN h4J/h
239 x 0.8
Tout = 60°C
45x 10x60 = IN
MI/h
IN = Gas input in MI/h 239 x 0.8
TE = 80% 27000 (Kcal/h)
= IN M/h
191.2
Q
= 10 L/min 141
UT/h
= IN
The Infinity 24 is able to modulate both the water and gas flows. The gas input varies depending on
the water flow and incoming and outgoing water temperatures. The chart on the following page is an
approximate guide to the gas input according to the various temperature rises and water flows.
To calculate the approximate gas input, first select the appropriate curve representing the water flow
in litres/minute p/min]. From the base line draw a vertical line at the point where the required
temperature rise in “C is indicated. This can be calculated by subtracting the incoming water
temperature from the selected temperature on the remote control. Draw a horizontal line from the
point where the vertical line intersects the curve. The point where the horizontal line intersects the
left hand vertical line (Gas Input), shows the approximate gas input in MI/h.

This chart is an approximate guide to the gas input according to various temperature rises and water
flows. See previous page, last paragraph for the explanation on how to calculate approximate gas
consumption in MI/h.
MJb (APPrW
190 I
5
10 15
20 25
30
35 40 45
50
55 60
Temp Rise
/+5Umin WEi/min 810Umin +12Umin 016Umin *21Umin
DEFAULT TEMPERATURE SETTING
On the P.C.B. there is a connection to which a plug or connector block can be fitted, [see diagram].
This connection locks the water temperature to a default setting in instances where no remote controls
are required. The default water temperature settings are:
60°C and 75°C.
Remote Control Faults
If the remote controls become faulty, the water heater
will not operate when a hot water tap is opened unless
these connections are bridged. The temperature of the
water will be maintained to the default water
temperature setting after bridging, depending on
which pins are bridged.
No Remote Control
In some applications remote controls may not be
required. In such cases the outgoing water temperature
will be governed by the default water temperature set
on the P.C.B. This provides a means to enable the
water temperatures to become tamper-proof.
l Disconnected 60%
l Conneceted 75%
Setting The Default Water Temperature Setting
l Bridging the two right hand pins gives a water temperature of WC.
l Bridging all three pins gives a water temperature of 75°C.

GAS AND WATER CONTROLS
Mechanical Water Regulator
The following graph shows the performance of the water regulator. The top line shows the
performance when the electronic water flow control is open, the lower line when it is closed. The
bottom line shows that with the electronic water flow control device closed, the maximum flow is 7
L/min.
This maximum flow is reached at 100 kPa inlet pressure. The top line shows that with the
electronic water flow control device open, the maximum flow is approximately 21
L/min. This
maximum flow is reached at 200 kPa inlet pressure.
Note: Although the Infinity 24 will operate at very low water pressures, maximum performance is
not reached unless the incoming pressure is 200 kPa or more.
Water Sensor
WATER PRESSURE
Water flow is detected by a turbine/magnetic pulse generating device. Water flows through the
turbine/magnetic sensor providing information to the P.C.B. by generating a predetermined number
of pulses in proportion to the water flow. See page 35, section 3, for pulses according to water flow
in L/min. These pulses are counted by the P.C.B. -
no pulse indicates no water flow. The frequency
of the magnetic pulses increases as the water flow increases, this enables the P.C.B. to calculate the
exact water flow, and determine the water flow in lines/minute.
As soon as the required water flow is detected, the
Turbine
P.C.B. activates the combustion fan. The combustion
fan speed is monitored by a magnetic pulse sensor.
The output from this sensor is processed by the
P.C.B. which opens the gas modulating valve to a
degree proportional to the fan speed. See also page 17
for further details on the combustion fan.
0

Electronic Water Flow Control Device
Water pressure to the appliance is controlled by a mechanical
diaphragm, spring and valve system. The water flow control
consists of a plug and barrel valve which is rotated by a motor to
increase or decrease the volume of water passing through the heat
exchanger.
.
lectronic water flow control valve
Geared motor
ater flow control valve
Inlet
P
80-
8
7
Inlet
The water flow through the heat exchanger is dependent on the
incoming and outgoing water temperatures, the P.C.B. controls the
settings of the water flow control valve to provide the correct flow
for the conditions at any given time. An
explanation on how to use
the chart below is at the top of the following page.
I
I
water valve opening
I
I
1
30’
60”
I
I
I 1
I
! Water valve
90” 120”
150”
180’ opening degree
1
1.5
I
II
I
1
2
2.5 3
3.5
4Ki-i
Potentiometer resistance

The water flow control device is controlled by a variable resistor (potentiometer). Use the chart on
page 16 to determine the approximate resistance of the potentiometer at a given water flow and
temperature rise. First determine the water flow from the unit. The tap must be turned on full, the
electronic water flow control device does not operate if flow is restricted at the tap. Using this
information draw a horizontal line from the ‘volume of hot water in
Ii&es/minute scale’ (upper
section -
left hand side of the chart), until it intersects the curved line of the chart. Subtract the
incoming water temperature from the preset temperature. Use this result to determine the electronic
water flow control device opening degree and approximate potentiometer resistance by drawing a
horizontal line from the point on the ‘pre-set temperature minus incoming water temperature scale’
(lower section - left hand side of the chart), until it intersects the straight line on the chart, and then
draw a vertical line until it meets the ‘potentiometer and opening degree’ indications at the bottom
of the chart. This vertical line indicates the correctresistance. Join-the intersecting points of the
curved and straight lines. An approximately verticalline indicates correct relationship between the
various data.
Combustion Fan
The air for combustion is supplied by a centrifugal fan driven by a DC motor. After a pre-purge
period of 1 second, the fan speed is controlled by the P.C.B. to provide the correct volume of air for
combustion. The calculation for the fan speed is based upon incoming water temperature, water flow
and the temperature selected on the remote controls.
The actual speed of the motor is continuously monitored by a magnetic pulse sensor. This sensor emits
4 pulses per rotation of the fan. This is the fan feedback or confirmation data processed by the P.C.B.
and used for 2 operations.
1) The fan speed is constantly corrected to provide optimum combustion conditions.
2) To determine the opening degree of the gas valves, so that the gas rate always matches the volume
of air for combustion, as well as the input required to heat the water.
The reason for controlling the
opening degree of the gas valves
based upon data from the
combustion fan is that the gas
valves are able to react much more
quickly to a change in control
signal than the combustion fan.
Controlling the gas valves based
upon data from the combustion fan
means that combustion remains
satisfactory,
even if there are
sudden changes in input conditions.
The combustion fan has a post purge period of 5 minutes, in other words, it runs on for 5 minutes
after the hot water tap is closed. The purpose of this feature is to provide instant ignition when the
hot water tap is turned ON and OFF repeatedly. This reduces the time taken to provide hot water; as
well as enabling the Infinity 24 to respond very quickly to repeated ON/OFF operations. During the
‘post purge’, the burner can light immediately the water tap is turned opened, without a pre-purge
period.