Rinnai REU-KA2530FFUD-US User manual

Key to Trade Names in this Manual:
RC & RU-Indicates condensing water heater
models.
Model with
valves in carton Equivalent Model
RC80e RC80HPe
RC80i RC80HPi
RC98e RC98HPe
RC98i RC98HPi
Some of the trade names for models were changed
to indicate that their cartons included isolation valves
and a pressure relief valve. For service and repair
purposes the table below shows the equivalent
models.
RC80HPe 915 20 22 25 28 31
RC80HPi 915 20 22 25 28 34
RC98HPe 11 16 20 22 25 28 37
RC98HPi 11 16 20 22 25 28 40
RU80e 13 17 21 23 27 29 43
RU80i 13 17 21 23 27 29 43
RU98e 13 17 21 23 27 29 43
RU98i 13 17 21 23 27 29 43
DIAGNOSTICS
WIRE DIAGRAM
GAS CONTROL
FAN
PC BOARD
WATER FLOW
CONTROL
HEAT
EXCHANGER
MODELS
This manual provides service information for the models
below. This table cross references each model to the
applicable page number for internal component
replacement instructions.
Condensing Tankless Water Heater Service Manual
KA Condensing KB Condensing
100000354

Condensing Water Heater Service Manual 2100000354
Table of Contents
General Information ................................................... 3
Specifications ............................................................. 4
Diagnostic Codes ....................................................4-8
Safety Warnings ......................................................... 9
Electrical Diagnostic Points
RC80HPe, RC80HPi ............................................ 10, 11
RC98HPe, RC98HPi ............................................ 12, 13
RU80e, RU80i, RU98e, RU98i ............................. 14, 15
Wire Diagrams
RC80HPe, RC80HPi .................................................. 16
RC98HPe, RC98HPi .................................................. 17
RU80e, RU80ic RU98e, RU98i .................................. 18
Flushing the Heat Exchanger.................................. 19
Manual Draining of the Water Heater ..................... 20
Gas Control Assembly
RC80HPe, RC80HPi, RC98HPe, RC98HPi............... 21
RU80e, RU80i, RU98e, RU98i ................................... 22
Fan
RC80HPe, RC80HPi, RC98HPe, RC98HPi............... 23
RU80e, RU80i, RU98e, RU98i ............................. 24, 25
PC Board
RC80HPe, RC80HPi, RC98HPe, RC98HPi............... 26
RU80e, RU80i, RU98e, RU98i ................................... 27
Water Flow Control Assembly
RC80HPe, RC80HPi, RC98HPe, RC98HPi............... 28
RU80e, RU80i, RU98e, RU98i ............................. 29, 30
Heat Exchanger
RC80HPe...............................................................31-33
RC80HPi................................................................34-36
RC98HPe...............................................................37-39
RC98HPi................................................................40-42
RU80e, RU80ic RU98e, RU98i .............................43-48
Gas Pressure Setting Procedure
RC80HPe, RC80HPi, RC98HPe, RC98HPi .........49, 50
RU80e, RU80i, RU98e, RU98i .............................52, 53
Manifold Pressure Settings
RC80HPe, RC80HPi, RC98HPe, RC98HPi ...............51
RU80e, RU80i, RU98e, RU98i ...................................54
Dip Switches
RC80HPe, RC80HPi, RC98HPe, RC98HPi ...............55
RU80e, RU80i, RU98e, RU98i ...................................56

Condensing Water Heater Service Manual 3100000354
General Information
Safety Definitions
This is the safety alert symbol. This symbol alerts you to potential hazards that can kill or hurt you and
others.
Indicates an imminently hazardous situation which, if not avoided, will result in death or
serious injury.
Indicates a potentially hazardous situation which, if not avoided, could result in death or
serious injury.
Indicates a potentially hazardous situation which, if not avoided, could result in minor or
moderate injury. It may also be used to alert against unsafe practices.
DANGER
CAUTION
WARNING
Recommended Tools
 Volt/Ohm/Amp meter with test probes
 Digital manometer or U tube type manometer with 14 inch water column (W.C.) scale, a hose and two 1/8 inch
taps
 assorted wrenches including a 3/16 Allen wrench
 assorted screw drivers
 leak solution or leak detector
 Teflon tape
Using this Manual
Repairs should be performed by a qualified service technician.
The following information can be referenced for additional information.
 Operation and Installation Manual
 Hot Water System Design Manual
 Technical Sheets
 Technical Bulletins
Technical Support
Technicians are available to assist in servicing issues. Contact Rinnai Technical Services at 1-888-746-6247.
WARNING
There are a number of live tests that are required when fault finding this product. Extreme care should be used at
all times to avoid contact with energized components inside the water heater. Before checking for resistance
readings disconnect the power source to the unit and isolate the item from the circuit (unplug it).
If any of the original wire as supplied with the appliance must
be replaced, it must be replaced with type 18 AWG wire or its
equivalent.
Label all wires prior to disconnection when
servicing controls. Wiring errors can cause
improper and dangerous operation.
CAUTION

Condensing Water Heater Service Manual 4100000354
Specifications
[1] Minimum activation flow is approximately 0.4 gallons/minute (1.5 liters/min); minimum flow is approximately
0.26 gallons/minute (1 liter/min).
[2] Max temperature is 185 ºF (85 ºC) with the MCC-91 controller for commercial and hydronic applications only.
Trade Name Model Max. BTU Min. BTU Max Flow [1]
gal/min (liters/min)
Temperature Range
RC80HPe,
RC80e REU-KA2530WD-US 157,000 9,500 (NG) 10,300 (LPG) 8.0 (30)
98 - 140 ºF (37-60 ºC) [2]
RC98HPe,
RC98e REU-KA3237WD-US 199,000 9,500 (NG) 10,300 (LPG) 9.8 (37)
RU80e REU-KB2530WD-US 152,000 15,200 8.0 (30)
RU98e REU-KB3237WD-US 199,000 15,200 9.8 (37)
Condensing Series - Residential or Commercial - Outdoor
Trade Name Model Max. BTU Min. BTU Max Flow [1]
gal/min (liters/min) Temperature Range
RC80HPi,
RC80i REU-KA2530FFUD-US 157,000 9,500 (NG) 10,300 (LPG) 8.0 (30)
98 - 140 ºF (37-60 ºC) [2]
RC98HPi,
RC98i REU-KA3237FFUD-US 199,000 9,500 (NG) 10,300 (LPG) 9.8 (37)
RU80i REU-KB2530FFUD-US 152,000 15,200 8.0 (30)
RU98i REU-KA3237FFUD-US 199,000 15,200 9.8 (37)
Condensing Series - Residential or Commercial - Indoor
Diagnostic Codes
The Rinnai water heater has the ability to check its own operation continuously. If a fault occurs, an error code
will flash on the display of the temperature controller. This assists with diagnosing the fault and may enable you
to overcome a problem without a service call.
Important Safety Notes
There are a number of (live) tests that are required when fault finding this product.
Extreme care should be used at all times to avoid contact with energized components
inside the water heater. Only trained and qualified service technicians should attempt to
repair this product. Before checking for resistance readings, disconnect the power
source to the unit and isolate the item from the circuit (unplug it).
WARNING
Accessing Operating Information
To display the most recent error codes press and hold the “On/Off” button for 2 seconds. While holding the “On/
Off” button press the ▲ button. The last 9 error codes will flash one after the other. To exit this mode press the
“On/Off” and ▲ button as before.
To display the water flow through the water heater press and hold the ▲ button for 2 seconds and without
releasing the ▲ button press the “On/Off” button.
To display the outlet water temperature press and hold the ▼ button for 2 seconds and without releasing the ▼
button press the “On/Off” button.
Models MC-91 and MCC-91 (KA Series)

Condensing Water Heater Service Manual 5100000354
Diagnostic Codes
1. Water Flow Begins.
•Water Flow Sensor sends pulses to the PC
Board.
•PC Board senses flow.
•Firing Sequence begins when the flow exceeds
the minimum activation flow rate.
2. Firing Sequence.
•PC Board monitors water temperature,
temperature set point, and water flow rate.
•Combustion fan energized. Purges combustion
chamber.
•Spark igniter begins sparking.
•Gas control valve opens to minimum fire rate.
•Flame rod(s) proves ignition.
•Spark igniter stops sparking.
3. Normal Operation.
•PC Board monitors flame rod, fan motor
frequency, outlet water temperature, controller
temperature set point and water flow rate.
•Gas control valve modulates gas input to
required firing rate.
•Combustion fan speed is adjusted for the
required firing rate.
•Water flow control valve is adjusted as needed.
4. Shut-down Sequence.
•Shut-down begins when the PC Board senses
the minimum flow rate which is 0.26 - 0.5 gpm
depending on model.
•Gas control valve closes.
•Water flow control valve resets to standby
position.
•Combustion fan runs for a short period of time
at low speed.
5. Standby Mode.
•PC Board monitors water temperature and
remote controls.
•Freeze protection is activated as needed.
Operation
To display the most recent error codes press and hold the “On/Off” button for 2 seconds. While holding the “On/
Off” button press the ▲ button. The last 9 error codes will flash one after the other. To exit this mode press the
“On/Off” and ▲ button as before.
To enter or exit the maintenance monitor information mode, press and hold the button for 2 seconds and
without releasing it press the ON/OFF button.
To obtain the water flow rate: press the or buttons until “01” displays. The water flow rate will then appear.
For example “58” means 5.8 gal/min.
To obtain the outgoing water temperature press the or buttons until “02” displays. The temperature will
appear in degrees Fahrenheit.
Models MC-91-2 and MCC-91-2 (KB Series)
Data UnitNo.
Water flow rate 0.1 gal/min01
Outgoing water temperature Degrees Fahrenheit02

Condensing Water Heater Service Manual 6100000354
Diagnostic Codes
Code Definition Remedy
03 Power interruption during Bath
Fill (Water will not flow when
power returns).
Turn off all hot water taps. Press ON/OFF twice.
05 Bypass Servo Replace Bypass Servo
10 Air Supply or Exhaust
Blockage Ensure Rinnai approved venting materials are being used. Check that nothing is blocking the flue inlet or exhaust.
Check all vent components for proper connections.
Ensure vent length is within limits.
Verify dip switches are set properly.
Check fan for blockage.
Check burner and heat exchanger fins for obstructions.
For condensing models, Burner Sensor Error (see code 31)
11 No Ignition Check that the gas is turned on at the water heater, gas meter, or cylinder.
Ensure gas type and pressure is correct.
Ensure gas line, meter, and/or regulator is sized properly.
Bleed all air from gas lines.
Verify dip switches are set properly.
Ensure appliance is properly grounded.
Disconnect EZConnect or MSA controls to isolate the problem.
Ensure igniter is operational.
Check igniter wiring harness for damage.
Check gas solenoid valves for open or short circuits.
Remove burner cover and ensure all burners are properly seated.
Remove burner plate and inspect burner surface for condensation or debris.
If flame is visible, check the flame rod circuit.
12 Flame Failure Check that the gas is turned on at the water heater and gas meter. Check for obstructions in
the flue inlet or outlet.
Ensure gas line, meter, and/or regulator is sized properly.
Ensure gas type and pressure is correct.
Bleed all air from gas lines.
Ensure Rinnai approved venting materials are used.
Ensure vent length is within limits.
Verify dip switches are set properly.
Ensure appliance is properly grounded.
Disconnect keypad.
Disconnect EZConnect or MSA controls to isolate the problem.
Check power supply for loose connections.
Check power supply for proper voltage and voltage drops.
Ensure flame rod wire is connected.
Ensure flame rod is in proper position (wire should connect at 6 o’clock position for KA series
and 12 o’clock position for KB series ).
Remove flame rod and check for carbon build-up; clean with sand paper or emery cloth.
Disconnect and reconnect all wiring harnesses on unit and PC board.
Check all components for electrical short.
Turn off gas, attempt to fire unit. Should unit have a code 12 there is some form of short
occurring. Should the unit have a code 11 there is a combustion issue.
Check gas solenoid valves for open or short circuits.
Remove burner plate and inspect burner surface and heat exchanger fins for condensation or
debris.
Check the ground wire for the PC board.
14 Thermal Fuse Check gas type of unit and ensure it matches gas type being used.
Check for restrictions in air flow around unit and vent terminal.
Check for low water flow in a circulating system causing short-cycling.
Ensure dip switches are set to the proper position.
Check for foreign materials in combustion chamber and/or exhaust piping.
Check heat exchanger for cracks and/or separations.
Check heat exchanger surface for hot spots which indicate blockage due to scale build-up.
Refer to instructions in manual for flushing heat exchanger. Hard water must be treated
to prevent scale build up or damage to the heat exchanger.
Measure resistance of safety circuit.
Ensure high fire and low fire manifold pressure is correct.
Check for improper conversion of product.

Condensing Water Heater Service Manual 7100000354
Code Definition Remedy
16 Over Temperature
Warning Check for restrictions in the intake and exhaust system. Check for low water flow in a circulating system causing short-cycling.
Check for foreign materials in combustion chamber and/or exhaust piping.
Check for blockage in the heat exchanger.
19 Electrical Grounding Check all components for electrical short.
25
Condensate Trap Error Condensate container is full. Check condensate drain for blockage.
Replace condensate trap.
31 Burner Sensor Error
Measure resistance of sensor. Replace sensor.
32 Outgoing Water
Temperature Sensor Check sensor wiring for damage. Measure resistance of sensor.
Clean sensor of scale build-up.
Replace sensor.
33 Heat Exchanger Outgoing
Temperature Sensor Check sensor wiring to be sure it has not been short circuited. Measure resistance of sensor.
Clean sensor of scale build-up.
Replace sensor.
41 Outside Temperature
Sensor Check sensor wiring for damage. Measure resistance of sensor.
Clean sensor of scale build-up.
Replace sensor.
51 Inlet Water Temperature
Sensor Check sensor wiring for damage. Measure resistance of sensor.
Clean sensor of scale build-up.
Replace sensor.
52 Modulating Solenoid
Valve Signal Abnormal Check modulating gas solenoid valve wiring harness for loose or damaged terminals. Measure resistance of valve coil.
57 Burner
(Bi-Metal sensors /
Thermal Fuse Harness)
Check for continuity through bi-metal sensors located at top of heat exchanger at white plastic
connector containing red an white wires.
58 Secondary Heat
Exchanger There is scale build-up in the secondary heat exchanger and it needs to be flushed to prevent damage. Refer to the flushing instructions in the manual. Hard water must be treated to prevent
scale build-up or damage to the heat exchanger.
61 Combustion Fan Failure Ensure fan will turn freely.
Check wiring harness to motor for damaged and/or loose connections.
Measure resistance of motor winding.
Check for proper voltage from PC board.
65 Water Flow Control The water flow control valve has failed to close during the bath fill function. Immediately turn off
the water and discontinue the bath fill function. Contact a state qualified or licensed contractor to
service the appliance.
70 Sensor Harness
Connection
Check PC board switches (in the bank of 6 switches, #2 should be on for indoor models and off for
outdoor models on KA series units only)
Check the connection harness at the E connection on the PC board. Outdoor models should have
2 orange cables at #7 and 8 positions. Indoor models should not have cables at these positions. If
this is incorrect then replace the sensor harness.
Replace PC board
71 Solenoid Valve Circuit Replace PC board.
72 Flame Sensing Device Verify flame rod is touching flame when unit fires.
Check all wiring to flame rod.
Remove flame rod and check for carbon build-up; clean with sand paper or emery cloth.
Check inside burner chamber for any foreign material blocking flame at flame rod.
Measure micro amp output of sensor circuit with flame present.
Replace flame rod.
Diagnostic Codes

Condensing Water Heater Service Manual 8100000354
73 Burner Sensor Circuit
Check sensor wiring and PC board to be sure they have not been damaged. Replace sensor.
79 Water Leakage Detected Turn off water and gas supply.
Disconnect power to the unit.
Inspect the unit for leak.
Dry area around moisture sensing element.
LC Scale Build-up in Heat
Exchanger (when
checking maintenance
code history, “00” is
substituted for “LC”)
Flush heat exchanger. Refer to instructions in manual. Hard water must be treated to prevent
scale build up or damage to the heat exchanger.
Replace heat exchanger.
NOTE: The LC code is the only code that will allow the unit to keep running. The display will
alternate between the LC code and the temperature setting. The controller will continue to beep.
FF Maintenance Performed Indicates a service provider performed maintenance or repair. Enter this code by pressing up,
down, and ON/OFF simultaneously.
No
code Nothing happens when
water flow is activated. On controller, verify if unit is sensing flow. If not then check the items below. If unit is
sensing flow then check the heat exchanger and outlet thermistors.
Clean inlet water supply filter.
On new installations ensure hot and cold water lines are not reversed.
Check for cold to hot cross over. Isolate circulating system if present. Turn off cold water to the
unit, open pressure relief valve; if water continues to flow, there is bleed over in your plumbing.
Verify you have at least the minimum flow rate required to fire unit.
Verify turbine spins freely.
Measure the resistance of the water flow control sensor.
If the display is blank and clicking is coming from the unit, disconnect the water flow servo motor.
If the display comes on then replace the water flow servo motor.
Diagnostic Codes

Condensing Water Heater Service Manual 9100000354
WARNING
Failure to correctly assemble the components according to the instructions contained within this service manual
may result in a gas leak or explosion.
WARNING
Inspect all gaskets/packings for signs of damage or corrosion. Gaskets/packings found to contain damage or that
appear questionable MUST BE REPLACED. Failure to replace damaged or questionable gaskets may result in
gas leak or explosion.
WARNING
Follow the steps below prior to servicing or replacing any component within the tankless water heater in order to
protect yourself from harm:
Turn off the electrical power supply by unplugging the power cord or by turning off the electricity at the circuit
breaker. (The temperature controller does not control the electrical power.)
Turn off the gas at the manual gas valve, usually located immediately below the water heater.
Turn off the incoming water supply. This can be done at the isolation valve immediately below the water heater or
by turning off the water supply to the building.
DO NOT proceed in performing any electrical
diagnostics, service repairs, or component replacements
without reading and following the warnings below.
STOP
DO NOT proceed in performing any electrical
diagnostics, service repairs, or component replacements
without reading and following the warnings below.
There are a number of (live) tests that are required when fault finding this product. Extreme care should be used
at all times to avoid contact with energized components inside the water heater. Only trained and qualified service
technicians should attempt to repair this product. Before checking for resistance readings, disconnect the power
source to the unit and isolate the item from the circuit (unplug it)
Important Safety Notes

Condensing Water Heater Service Manual 10 100000354
Heat Exchanger and Outgoing Water Temperature
Thermistors:
Check all thermistors by inserting meter leads into
each end of the thermistor plug. Set your meter to the
20 K scale and read resistance. Applying heat to the
thermistor bulb should decrease the resistance.
Applying ice to the thermistor bulb should increase the
resistance.
*Example:
140°F = 2.2 ~ 2.7K
221°F = 0.6 ~ 0.8K
59°F = 11.4 ~ 14K
86°F = 6.4 ~ 7.8K
113°F = 3.6 ~ 4.5K
KA Series Electrical Diagnostic Points
RC80HPe, RC80HPi
Frost Protection:
This unit has frost protection heaters mounted at
different points to protect the water heater from
freezing.
Amp Fuses:
This unit has one inline (7) amp glass fuse. Remove
the fuse and check continuity through it. If you have
continuity through the fuse then it is good. Otherwise
the fuse is blown and must be replaced.
Flame Rod:
Place one lead of your meter to the flame rod and the
other to ground. With the unit running you should read
between 5-150 VAC. Set your meter to the micro amp
scale. You should read a minimum of 1 micro amp for
proper flame circuit. In the event of low flame circuit
remove the flame rod and check for carbon or damage.
COMPONENT MEASUREMENT POINT RANGE OF VALUE
CN PINS WIRE COLOR
TEMP CONTROLLER A1-3Bk-Bk DC10-13V
THERMAL FUSE B1 pin1 to E1 pin 1 R-RBELOW 1 Ω
MOD. SOLE. VALVE (POV) B2 (1-2), B (10-11) B2: O-ODC2-15V / 67-82 Ω
MAIN SOLE. VALVE (SV0) B5 (1-2), B (7-8) B5: P-Bk
DC11-13V / 37-43 Ω
SOLENOID VALVE 1 B6 (1-2), B (6-7) B6: B-Bk
SOLENOID VALVE 2 B7 (1-2), B (5-7) B7: Y-Bk
SOLENOID VALVE 3 B3 (1-2), B(4-7) B3: R-Bk
SOLENOID VALVE 4 B4 (1-2), B(3-7) B4: O-Bk
SURGE PROTECTOR C1 1-3Bk-WAC108-132V
SURGE PROTECTOR C2 1-3W-W
ANTI FROST HEATER
HOT WATER OUTLET LINE 10-20 Ω
HEAT EXCHANGER PIPING 35-50 Ω
WATER FLOW SENSOR, HOT WATER OUT-
LET, DRAIN CONNECTION 110-150 Ω
LATENT HEAT EXCHANGER (INDOOR MOD-
EL ONLY) 90-110 Ω
IGNITOR D1 1-2Gy-Gy AC108-132V
(DURING IGNITION)
HEAT EXCHANGER TH W-W15ºC/59ºF: 11.4-14.0 kΩ
30ºC/86ºF: 6.4-7.8 kΩ
45ºC/113ºF: 3.6-4.5 kΩ
60ºC/140ºF: 2.2-2.7 kΩ
105ºC/221ºF: 0.6-0.8 kΩ
E2 (1, 2), E(5-10)
OUTGOING WATER TH1 E3 1-2W-W
OUTGOING WATER TH2 E4 3-4W-W

Condensing Water Heater Service Manual 11 100000354
COMPONENT MEASUREMENT POINT RANGE OF VALUE
CN PINS WIRE COLOR
WATER FLOW SENSOR E5
1-3R-Bk DC11-13V
2-3Y-Bk DC4-7V; 1-1.4 MΩ
BYPASS FLOW CONTROL G1
1-5Br-W
DC2-6V DURING OPERATION
15-35 Ω
2-5O-W
3-5Y-W
4-5R-W
WATER FLOW CONTROL G2
3 or 4 - 8 R or P -ODC5-7V DURING OPERATION
1 or 2 - 8 B or W -O
3-4R-P30-50 Ω
1-2B-W
7-5Y-Gy BELOW DC1V (LIMITER ON)
DC0-6 (LIMITER OFF)
7-6Br-Gy
COMBUSTION FAN L1
1-2R-Bk DC6-45V
2-3Y-Bk DC11-13V; 3.5-3.9 kΩ
2-4W-Bk DC5-10V; 9.2-9.4 kΩ;
(PULSE 20-420 Hz)
KA Series Electrical Diagnostic Points
RC80HPe, RC80HPi

Condensing Water Heater Service Manual 12 100000354
Heat Exchanger and Outgoing Water Temperature
Thermistors:
Check all thermistors by inserting meter leads into
each end of the thermistor plug. Set your meter to the
20 K scale and read resistance. Applying heat to the
thermistor bulb should decrease the resistance.
Applying ice to the thermistor bulb should increase the
resistance.
Frost Protection:
This unit has frost protection heaters mounted at
different points to protect the water heater from
freezing.
KA Series Electrical Diagnostic Points
RC98HPe, RC98HPi
Amp Fuses:
This unit has one inline (7) amp glass fuse. Remove
the fuse and check continuity through it. If you have
continuity through the fuse then it is good. Otherwise
the fuse is blown and must be replaced.
Flame Rod:
Place one lead of your meter to the flame rod and the
other to ground. With the unit running you should read
between 5-150 VAC. Set your meter to the micro amp
scale. You should read 1 micro amp for proper flame
circuit. In the event of low flame circuit remove the
flame rod and check for carbon or damage.
COMPONENT MEASUREMENT POINT RANGE OF VALUE
CN PINS WIRE COLOR
TEMP CONTROLLER B1 1-3Bk-Bk DC10-13V
THERMAL FUSE E1 pin 1 to B1 pin 1 R-WBELOW 1 Ω
MOD. SOLE. VALVE (POV) B2 1-2O-ODC2-15V / 67-81 Ω
MAIN SOLE. VALVE (SV0) B3 1-2P-Bk DC11-13V / 24-28 Ω
SOLENOID VALVE 1 B4 1-2Bl-Bk
DC11-13V / 37-43 Ω
SOLENOID VALVE 2 B5 1-2Y-Bk
SOLENOID VALVE 3 B6 1-2R-Bk
SOLENOID VALVE 4 B7 1-2O-Bk
SURGE PROTECTOR C1 1-3Bk-WAC108-132V
SURGE PROTECTOR C2 1-3W-W
ANTI FROST HEATER
HOT WATER OUTLET LINE 180-207 Ω
HEAT EXCHANGER PIPING 156-180 Ω
WATER FLOW SENSOR 24-28 Ω
IGNITOR D1 1-2Gy-Gy AC90-110V
(DURING IGNITION)
HEAT EXCHANGER TH E2 1-2W-W15ºC/59ºF: 11.4-14.0 kΩ
30ºC/86ºF: 6.4-7.8 kΩ
45ºC/113ºF: 3.6-4.5 kΩ
60ºC/140ºF: 2.2-2.7 kΩ
105ºC/221ºF: 0.6-0.8 kΩ
OUTGOING WATER TH1 W-WE4 pins 3,4 to E8 pins 1-2

Condensing Water Heater Service Manual 13 100000354
COMPONENT MEASUREMENT POINT RANGE OF VALUE
CN PINS WIRE COLOR
WATER FLOW SENSOR F2
1-3R-Bk DC11-13V; 5.5-6.2 kΩ
2-3Y-Bk DC4-7V; 1-1.4 MΩ
BYPASS FLOW CONTROL G1
1-5Br-W
DC2-6V DURING OPERATION
15-35 Ω
2-5O-W
3-5Y-W
4-5R-W
WATER FLOW CONTROL G2
3 or 4 - 8 R or P -ODC5-7V DURING OPERATION
1 or 2 - 8 B or W -ODC5-7V DURING OPERATION
3-4R-P30-50 Ω
1-2B-W30-50 Ω
7-5Y-Gy BELOW DC1V (LIMITER ON)
DC0-6 (LIMITER OFF)
7-6Br-Gy BELOW DC1V (LIMITER ON)
DC0-6 (LIMITER OFF)
COMBUSTION FAN E1
1-2R-Bk DC6-45V
2-3Y-Bk DC11-13V; 3.5-3.9 kΩ
2-4W-Bk DC5-10V; 9.2-9.4 kΩ;
(PULSE 20-420 Hz)
KA Series Electrical Diagnostic Points
RC98HPe, RC98HPi

Condensing Water Heater Service Manual 14 100000354
KB Series Electrical Diagnostic Points
RU80i/e, RU98i/e
Heat Exchanger, Outgoing Water Temperature and
Inlet Thermistors:
Check all thermistors by inserting meter leads into each
end of the thermistor plug. Set your meter to the 20 K
scale and read resistance. Applying heat to the
thermistor bulb should decrease the resistance. Apply-
ing ice to the thermistor bulb should increase the
resistance. See below for examples of typical
temperatures and resistance readings.
*Example:
140°F = 2.2 ~ 2.7K
221°F = 0.6 ~ 0.8K
59°F = 11.4 ~ 14K
86°F = 6.4 ~ 7.8K
113°F = 3.6 ~ 4.5K
Flame Rod:
Place one lead of your meter to the flame rod and the
other to ground. With the unit running you should read
between 5-150 VAC. Set your meter to the μ amp scale
and series your meter in line with the flame rod. You
should read 1 μ amp or greater for proper flame circuit.
In the event of low flame circuit remove the flame rod
and check for carbon or damage.
Frost Protection:
This unit has frost protection heaters mounted at
different points to protect the water heater from freezing.
All of them should show a positive resistance reading.
Amp Fuses:
This unit has one inline (10) amp glass fuse. Remove
the fuse and\ check continuity through it. If you have
continuity through the fuse then it is good. Otherwise the
fuse is blown and must be replaced.
Wire Color Voltage Resistance Connector # Pin #’s
(Main) Black - Pink 11 ~ 13 VDC 24 ~ 28 ohms B1 3 - 4
(SV1) Black - Blue 11 ~ 13 VDC 35 ~ 41 ohms B3 4 - 6
(SV2) Black - Yellow 11 ~ 13 VDC 35 ~ 41 ohms B2 4 - 7
(SV3) Black - Red 11 ~ 13 VDC 39 ~ 42 ohms B4 4 - 5
(POV) Yellow - Yellow 2 ~ 15 VDC 67 ~ 81 ohms D4 1 - 2
(SV1, SV2, SV3 and POV) Gas valve and Modulating solenoids: (Set meter below 2K)
Red - Pink 5 ~ 8 VDC 24 ~ 28 ohms G2 3 - 4
White - Blue 5 ~ 8 VDC 35 ~ 41 ohms G2 1 - 2
Grey - Brown N/A N/A G2 5 - 7
Grey - Orange N/A N/A G2 6 - 7
(M) Water Flow Control Device Servo or Geared Motor:
NOTE: The grey wire listed above turns to black at G connector on the PCB.

KB Series Electrical Diagnostic Points
RU80i/e, RU98i/e
Wire Color Voltage Resistance Connector # Pin #’s
Black - Red 11 ~ 13 VDC 5.5 ~ 6.2 K ohms L3 E10 - G7
Yellow - Black 4 ~ 7 VDC 1 ~ 1.4 Mega ohms B3 4 - 6
(QS) Water Flow Sensor:
Red - Pink 2 ~ 6 VDC 44 ~ 52 ohms G1 12 - 13
Yellow - Black 2 ~ 6 VDC 44 ~ 52 ohms G1 10 - 11
By-Pass Flow Control:
Grey - Grey 90 ~ 110 VAC N/A C1 1 - 3
(IG) Ignition System:
Red - Black 6 ~ 45 VDC N/A L2 5 - 6
White - Black 5 ~ 10 VDC 9.72 ~ 9.75 K ohms L2 3 - 5
Yellow - Black 11 ~ 13 VDC 4.02 ~ 4.05 K ohms L2 4 - 5
(FM) Combustion Fan Motor:
Set your meter to the hertz scale. Reading across the white and black wires at terminals 3 and 5 you
should read between 60 and 420 hertz.
Red - White 11 ~ 13 VDC Below 1 Ohms B8
B7 B1 - G8
Thermal Fuse / Overheat Switch:
White - White N/A *See example on
page 11 E6 2 - 3
Blue - Blue N/A *See example on
page 11 E6 4 - 5
Outgoing Water Thermistor:
Pink - Pink N/A *See example on
page 11 E5 4 - 7
Heat Exchanger Temperature Thermistor:
White - White N/A *See example on
page 11 E9 4 - 9
Inlet Thermistor:
Terminals J 10 ~ 13 VDC 1.5 ~ 3.0 K ohms J1 - 2
Remote Control:

Condensing Water Heater Service Manual 16 100000354
KA Series Wiring Diagram
RC80HPe, RC80HPi

Condensing Water Heater Service Manual 17 100000354
KA Series Wiring Diagram
RC98HPe, RC98HPi

Condensing Water Heater Service Manual 18 100000354
KB Series Wiring Diagram
RU80i/e, RU98i/e

Condensing Water Heater Service Manual 19 100000354
An “LC” or “00” error code indicates the unit is beginning to lime up and must be flushed. Failure to flush the
appliance will cause damage to the heat exchanger. Damage caused by lime build-up is not covered by the unit’s
warranty. After flushing, reset the LC fault code by turning off the power to the unit and turning the power back
on.
Flushing the Heat Exchanger
Water Heater
Pressure Relief Valve
3/4" Ball Valve
3/4" Union
Check Valve S
Pressure Regulator
Circulating Pump
Solenoid Valve
Boiler Drain Valve
KEY
G a s
Sup
p ly
V1
V3
V2
V4
H1
H2
H3
Circulating Pump
Cold
Water
Line
Hot
Water
Lin
e
n
-line
Filter
I
Rinnai
1. Disconnect electrical power to the water heater.
2. Close the shutoff valves on both the hot water and
cold water lines (V3 and V4).
3. Connect pump outlet hose (H1) to the cold water line
at service valve (V2).
4. Connect drain hose (H3) to service valve (V1).
5. Pour 4 gallons of undiluted virgin, food grade, white
vinegar into pail.
6. Place the drain hose (H3) and the hose (H2) to the
pump inlet into the cleaning solution.
7. Open both service valves (V1 and V2) on the hot
water and cold water lines.
8. Operate the pump and allow the cleaning solution to
circulate through the water heater for at least 1 hour
at a rate of 4 gallons per minute (15.1 liters per
minute).
9. Turn off the pump.
10. Rinse the cleaning solution from the water heater as
follows:
a. Remove the free end of the drain hose (H3) from
the pail. Place in sink or outside to drain.
b. Close service valve, (V2), and open shutoff valve,
(V4). Do not open shutoff valve, (V3).
c. Allow water to flow through the water heater for 5
minutes.
d. Close shutoff valve (V4). When unit has finished
draining remove the in-line filter at the cold water
inlet and clean out any residue. Place filter back
into unit and open valve (V4).
e. Close service valve, (V1), and open shutoff valve,
(V3).
11. Disconnect all hoses.
13. Restore electrical power to the water heater.

Condensing Water Heater Service Manual 20 100000354
If the water heater is not going to be used during a period of
possible freezing weather, it is recommended that the water
inside the water heater be drained.
To manually drain the water:
1. Shut off cold water supply, hot water valve and gas supply.
2. Turn off the temperature controller.
3. Disconnect the power to the water heater.
4. Remove the drain caps on both isolation valves and open
both valves above the caps (blue and red valve handles).
-OR- Open hot water drain plug at the hot water outlet.
5. Remove water filter to drain the cold water.
6. Unscrew the water drain plug from the drain line next to
the hot water outlet and remove the condensate trap drain
plug. Allow to drain.
To resume normal operation:
1. Confirm that all water drain plugs are removed, that the
gas supply is turned off, and that all taps are closed.
2. Insert the condensate trap drain plug and screw in the
water drain plug.
3. Screw in the water filter in the cold water inlet.
4. Replace the drain caps and close both isolation valves. -
OR- Screw in the hot water drain plug.
5. Open the cold water supply and hot water valve.
6. Open a tap and confirm that water flows, and then close.
7. Turn on the power.
8. After confirming that the temperature controller is off, turn
on the gas supply.
9. Turn on the temperature controller.
Running a low volume of water through the water heater to prevent freezing
If the temperature exceeds the ability of the water heater to freeze
protect itself, or if power is lost, the following steps may prevent the
water heater and external piping from freezing. (Units connected with
EZConnect™ should be drained to prevent freezing if not in use.)
1. Turn the water heater off.
2. Close the gas supply valve.
3. Turn on a hot water tap to flow water about 0.1 gal/min or where
the stream is about 0.2 inches thick.
When the water heater or external piping has frozen
1. Do not operate the water heater if it or the external piping is frozen.
2. Close the gas and water valves and turn off the power.
3. Wait until the water thaws. Check by opening the water supply valve.
4. Check the water heater and the piping for leaks.
HOT
COLD
ON!
0.1 gal/min or
about 0.2 inch
thick
To avoid burns, wait until the equipment cools down before draining the water. The
water in the appliance will remain hot after it is turned off.
WARNING
* Use a wrench or other tool to unscrew the
hot water drain plug.
Water
filter
Condensate
trap drain plug
Hot water
outlet Hot water
drain plug*
Cold water
inlet
Water
drain
plug
(KA Series)
Manual Draining of the Water Heater
Water
drain plug
Condensate
trap drain plug
Condensate
drain line
Gas
connection Cold water
inlet
Hot water
outlet
(KB Series)