TROUBLESHOOOTING BOILER

Table of Contents

BLOCKING CODES

BL-01Indicates that the contact on terminals 24 and 25 are open:3

BL-05 Refers to Outdoor Temp. Sensor not communicating back to the boiler4

BL-11 Refers to ∆T between the T1 & T2 greater than 64°F in heat Call5

BL-12 Refers to ∆T between T1 & T2 sensors greater than 64*F in a call for DHW6

BL-67 Refers ∆T of at least 9F between T1 & T2 while burner not in operation. 7

BL-81 Diagnosing and resetting the BL81 blocking code:9

BL-85 Indicates no circulation is detected10

BL-86 Indicates frequency of power supply deviates +/- 1.5 HZ11

ERROR CODES

E-02 Indicates No flame Information13

E-03 Indicates Control unit error16

E-04 Indicates the controller has detected a program error17

E-05 Indicates fluctuations of incoming power in excess of +/-10%.18

E-12 Indicates high limit switch activated due to excessive temperature20

E-14Indicates T3 Flow sensor ground connection/failure or Controller failure 23

E-18 Indicates T1 sensor has read a value of more than 212°F25

E-19 Indicates T2 sensor reading a value of more than 212°F.27

E-24Indicates T2 sensorvalue is 50°F above T1 sensor for a fixed time.30

E-28 Indicates fan is not communicating back to the MCBA 33

E-29 Indicates tachometer signal from fan to MCBA is >150 RPM’s on standby.34

E-31 Refers to a faulty T1 Supply sensor35

E-32 Refers to a short at the T2 return sensor:37

E-36 Refers to an “open” sensor reading from the T1 Supply sensor38

E-37 Refers to an “open” sensor reading from the T2 return sensor39

E-68 Refers to no software being present on both the MCBA 41

E-69 Refers to no software, no display, or wrong display present42

(1 0f 1)BL-01

BL-01 code indicates that the contact on terminals 24 and 25 are open:

  1. If an external safety device is not being used, make sure that the default jumper was installed on terminals 24 and 25. If not, install a jumper across these two terminals.
  2. If an external safety device is being used, such as a low water cut-off or an external high limit switch perform the following.
  3. Verify the low water cut-off (LWCO) and high temperature limit switch (HTLS) was installed per Rinnai’s installation instructions found in the product’s manual.
  4. Verify the LWCO and HTLS is wired per the manufacturer’s instructions.
  5. If a 24 volt power supply is needed to power the LWCO, install an external transformer (field supplied). Do not connect the LWCO or HTLS to a 24 volt power supply on the boiler.
  6. Verify that the LWCO and HTLS is powered up and operating correctly.
  7. Check all wiring to the LWCO and HTLS for loose, broken or damage connections, repair as necessary.
  8. If the LWCO contact is open due to a low water condition in the system, check the boiler and heating system for any signs of leaks. Repair any leaks found, refill the system to the proper operating pressure. Re-fire the boiler and check for proper operation.
  9. Check to see if the HTLS contact is open. If so, allows it to cool down and see if the contact closes, if not replace the HTLS. Re-fire the boiler and check for proper operation.
  1. If the boiler is still displaying a Blocking Code of BL01 perform the following:
  2. Disconnect wires from terminals 24 & 25, install a jumper wire across those two terminals, this will jump out the LWCO and HTLS.
  3. Fire the boiler, if it operates without displaying a BL01 code the issue is in your safety circuit being a bad wire connection, open contact in the LWCO or HTLS or a defective LWCO or HTLS. Locate the issue by ohming out the wires and/or contacts on your LWCO or HTLS. Replace defective wiring or switches.
  4. Re-install the wires on terminals 24 & 25. Fire up the boiler; if the code reappears verify the temperature setting of your aquastat was set to the proper setting. It must be set above the maximum temperature setting at PARA 1 on the boiler.
  5. If the code BL01 re-appears locate the cause of the over-temping, could be a zone valve, air in the system, circulator, valves shut off, 3-way valve, etc.). Make the necessary repairs; boiler should be functional at this point.

(1 0f 1)BL-05

BL-05 is a blocking code that refers to the Outdoor Temperature Sensor not communicating back to the boiler

  1. Outdoor Temperature Sensors are required by code per the Department of Energy, (DOE) to be installed on all boilers after October 2012. Verify your boiler has this component installed/connected to the boiler.
  2. If the boiler does not have this component installed on it and it is flashing BL05, Rinnai recommends you install the outdoor temperature sensor, part# 805000047. Even on units manufactured and installed before the date mentioned above.
  3. If the outdoor temperature sensor is installed and the boiler is flashing a BL05 code, perform the following checks:
  4. Verify the wires from the outdoor sensor are connected to terminals 18 and 19 on the boiler.
  5. Inspect the wiring from the outdoor temperature sensor back to the boiler for any signs of loose, damaged or broken wires or connections. Repair or replace wiring if necessary.
  6. If no defective wiring is found, remove the wires from the outdoor sensor at the sensor. Using a multimeter set to Ohms, read the resistance between the two terminals on the sensor. This is a 12K Ohm NTC sensor, (see chart on next page for proper values). If the reading on the meter shows the sensor to be “open” or “short”, replace it.
  7. Verify the outdoor temperature sensor is installed well above the anticipated snow load or drifting snow. Relocate the sensor if there is any possibility of it being submerged by snow.
  8. Verify the outdoor temperature sensor is installed so it is not in direct contact with the sun. If so, relocate the sensor as the heat from the sun with affect the reading of said sensor.

(1 0f 1) BL-11

BL-11 Code refers to a delta T between the T1 supply and T2 return sensors greater than 64*F in a call for Central Heating.

  1. Verify all air has been purge from the heating system piping, purge if necessary.
  2. On boilers where the Low Loss Header (LLH) or where primary/secondary piping is not being utilized verify that all valves are open and the system pump is operational.
  3. For all boiler series:
  4. Disconnect power to the boiler
  5. Isolate the boiler using ball valves installed under the boiler.
  6. Check the boiler strainer for any blockage or debris. If debris is found in the strainer back flush the boiler with water. (Do not use chemical cleaners of any kind, as they are not approved for use in the boiler and may cause damage to the boiler’s heat exchanger).
  7. With the boiler drained down, check for sediment buildup on the pump’s impeller. Clean or replace as necessary.
  8. Inspect the air vent on top of the heat exchanger, replace if damaged or leaking.
  9. Remove the 3-way valve actuator motor, if installed. Manually exercise the spring loaded plunger, checking to see if it is binding.

→If the valve shows signs of binding or sticking, remove the cartridge, using valve grease lubricate the assembly and then reinstall the components. If it continues to bind, replace the cartridge.

  1. Refill the boiler and the system side of the boiler to 16—18 psi of water pressure.
  2. On an E-Series boiler make sure that the circulator is set to III or high speed.
  3. After the de-aeration cycle (17 minutes), create a call for heat.
  4. Verify the boiler pump is operational. If not, check to ensure you have 120 VAC to the pump.

If the pump has 120 VAC, check to ensure pump impeller spends freely, if so replace the pump.

  1. If the issue is happening in a call for domestic heat on the E or Q-Series boiler, there may be restriction within the boiler system or heat exchanger.
  2. If the system has PEX piping installed, verify that it has an O2 barrier. If not, the system will have to be separated by the use of a flat plate heat exchanger to reduce corrosion within the boiler.

(1 0f 1) BL-12

BL-12 Code refers to a delta T between the T1 supply and T2 return sensors greater than 64*F in a call for DHW.

  1. On all boilers where an indirect domestic hot water tank is installed perform the following.
  2. Verify all air has been purge from the domestic hot water loop, purge if necessary.
  3. Verify the pump for the tank was sized correctly.
  4. Verify that all valves are open and the system pump is operational.
  5. For all boiler series:
  6. Disconnect power to the boiler.
  7. Isolate the boiler using ball valves installed under the boiler.
  8. Check the boiler strainer for any blockage or debris. If debris is found in the strainer back flush the boiler with water. (Do not use chemical cleaners of any kind, as they are not approved for use in the boiler and may cause damage to the boiler’s heat exchanger).
  9. With the boiler drained down, check for sediment buildup on the pump’s impeller. Clean or replace as necessary.
  10. Inspect the air vent on top of the heat exchanger, replace if damaged or leaking.
  11. Remove the 3-way valve actuator motor, if installed. Manually exercise the spring loaded plunger, checking to see if it is binding.

→If the valve shows signs of binding or sticking, remove the cartridge, using valve grease lubricate the assembly and then reinstall the components. If it continues to bind, replace the cartridge.

  1. Refill the boiler and the system side of the boiler to 16—18 psi of water pressure.
  2. On an E-Series boiler make sure that the circulator is set to III or high speed.
  3. After the de-aeration cycle (17 minutes), create a call for heat.
  4. Verify the boiler pump is operational. If not, check to ensure you have 120 VAC to the pump.

If the pump has 120 VAC, check to ensure pump impeller spins freely, if so replace the pump.

  1. If the issue is happening in a call for domestic hot water on the E or QP-Series boiler, the flat plate heat exchanger may be clogged with sediment or scale built up on the boiler side.
  2. Remove, inspect and clean the flat plate heat exchanger or replace if necessary.
  3. 5. If you are still getting a BL12 code, there may still be a restriction within the boiler.
  4. If the system has PEX piping installed, verify that it has an O2 barrier. If not, the system will have to be separated by the use of a flat plate heat exchanger to reduce corrosion within the boiler.

(1 0f 2) BL-67

BL-67 Code indicates a difference of at least 9F has been detected between the supply (T1) and return (T2) sensor while the burner is not in operation.

  1. First determine what temperature the boiler measured at the T1 and T2 sensors. Press and hold the “MODE” button for 5 seconds until “CODE” appears. After a brief period “C xxx” should come up on the display on the boiler. Next, press the “RADIATOR” button until the screen displays C 123. Next, press the “STORE” button until the display blinks. Now press the “MODE” button again until “INFO” is displayed on the screen. Then press the “STEP” button until you see a 1 with a value next to it. That is the boiler temperature the boiler sensed on the T1 supply sensor, record the temperature reading. Next press the “STEP” button until a 4 appears with a value next to it, that’s the temperature the boiler sensed at T2, record this read out. Now measure the resistance value of the T1 and T2 sensor and verify the resistance value is within the measured temperatures you recorded for each sensor. See resistance and temperature chart on next page.
  2. If the resistance value matches the sensed temperature you recorded for the T1 and T2 sensors, determine what else could be causing the temperature increase while the burner is not in operation. Check for any external heat sources around the boiler that could be causing this issue.
  3. If the resistance value/temperature chart for said temperature does not match the measured temperature check all Molex connectors for the T1 and T2 sensor for any signs of corrosion. Next, check all Molex connectors at the sensors and MCBA board for loose, broken or damage wires, pins, fittings or connectors.
  4. If you find the measured temperature and converted resistance value temperature are significantly different do the following.
  5. Replace the faulty sensor.
  6. Replace the wiring diagram.

(1 0f 2) BL-67

Values listed below are for the following sensors—T1 Supply Sensor, T2 Return Sensor, T3 DHW Sensor, T4 Outside Sensor and T5 Flue Gas Sensor

Temperature °F / Value in resistanceresistance
-4 / 99,000
-0.4 / 90,000
3.2 / 82,000
6.8 / 74,00
10.4 / 66,000
14 / 58,000
17.6 / 53,500
21.2 / 49,000
24.8 / 45,000
28.4 / 40,500
32 / 36,000
35.6 / 33,500
39.2 / 30,900
42.8 / 28,200
46.4 / 25,600
50 / 23,000
53.6 / 21,400
57.2 / 19,900
60.8 / 18,100
64.4 / 16,600
68 / 15,000
71.6 / 14,000
75.2 / 12,900
Temperature °F / Value in resistance
78.8 / 11,900
82.4 / 10,850
86 / 9,800
89.6 / 9,100
68 / 15,000
71.6 / 14,000
75.2 / 12,900
78.8 / 11,900
82.4 / 10,850
86 / 9,800
89.6 / 9,100
93.2 / 8,500
96.8 / 7,900
100.4 / 7,200
104 / 6,500
113 / 5,600
122 / 4,600
131 / 4,000
140 / 3,400
158 / 2,300
176 / 1,700
194 / 1,300

(1 0f 1)BL-81

BL-81 Diagnosing and resetting the BL81 blocking code:

  1. Check to ensure the Q-Series boiler has a jumper installed in the 2 pin connector on the left side of boiler heat exchanger. On the E-Series check to ensure there is no jumper at this connector.
  2. Verify no other component has been connected to the flue gas Molex connector prior to the code, such as the T1 flow sensor which is frequently connect to the flue gas connector by mistake.
  3. Inspect the flue gas sensor’s connector for signs any signs of corrosion or moisture.
  4. Clean the connector if wet/corroded.
  5. Re-fire the boiler.
  6. If the BL81 code reappears, press the reset button for no longer than (1) second to reset the boiler.
  7. Enter the “007” access code to edit Parameter 80.
  8. Press and hold the MODE button until the word “CODE” flashes on the screen.
  9. Use the RADIATOR/SHOWER HEAD buttons to enter the Access Code “C007”.
  10. Store the code by pressing the SNOWFLAKE button for 2 seconds, display will flash blank and light back up.
  11. Press the MODE button 1 time, display will read PARA.
  12. Press the STEP button to navigate to parameter 80.
  13. Set parameter 80 to “00” for E series without the jumper installed. On Q-Series set it to parameter 80 to “20” with the jumper installed.
  14. Create a call for heat. If the boiler fires and operates without throwing a BL81 code, the unit is ready to place back into operation. If the BL81 code returns, order jumper wire part #805000051. Place jumper shown with red arrow into the flue gas connector plug shown below.


(1 0f 1)BL-85

BL-85 code indicates no circulation is detected.

  1. Proceed with the following:
  2. Verify circulator pump has 120 VAC on the gray and brown wires on the Molex connector at the pump on call for heat.
  3. Verify the circulator pump impeller spins freely with a small flat bladed screwdriver. This can be accomplished by removing the slotted screw from the end of the pump motor and turning the pump shaft with the screwdriver.
  4. On a call for heat try bleeding all air from the boiler system.
  5. Verify the air vent on the top right side of the boiler’s heat exchanger is not clogged.
  6. Remove the internal filter screen and check for debris buildup, clean as necessary.
  7. Verify the inlet screen to the 3-way valve is not clogged with debris.
  8. Verify the boiler’s plate heat exchanger is not clogged up, if equipped.
  9. Verify the boiler’s pressure switch is not clogged, remove and inspect plunger.
  10. Verify the boiler’s heat exchanger is not clogged with debris, back flush as needed.
  11. After verifying all of the above inspections, turn the boiler back on and allow it to go through the 17 minute de-aeration cycle. If the boiler still continues to display BL-85, replace the pressure switch.

(1 0f 1) BL-86

BL-86 code indicates the frequency of the power supply to the boiler is deviates more than plus or minus 1.5 HZ or less than 57.5 HZ and more than 62.5 HZ).

  1. Check the main power supply with a meter capable of reading Hertz. The most common cause for the BL-86 is an unstable power supply from an alternate power supply such as:
  2. Generators
  3. Solar Panels
  4. Wind generated power

→This is important to maintain between 57.5 to 62.5 Hertz.


(1 0f 3) E-02

E-02 Code indicates No flame Information

  1. Verify inlet gas pressure with all gas appliances at the installation site firing on high fire. Natural gas pressure should maintain between 4 -10.5” W.C., Propane gas should be between 8—14” W.C.
  1. If your inlet gas pressure is correct restrict the air inlet of the appliance by 50% with your hand over the attenuator on the left side of the unit. Next, re-fire the unit, if the unit fires slowly remove your hand from the intake. If the burner stays running check and/or adjust your O2 readings per Rinnai installation instructions found in the owner’s installation manual. If the unit shuts off immediately after removing your hand from the air in-take on new LP installations, verify you do not have a gas quality issue. Verify the propane tank was properly purged and the gas mixture is correct.
  1. Check for cross contamination from exhaust gases being drawn back into the inlet air on the vent termination. Next, inspect the plastic venture were air enters the gas valve and fan assembly for damage. If the plastic venture is damaged, you will not be able to commission the boiler properly. Replace damaged component then re-commission your boiler.
  1. If the unit fires normally and then drops out on E02, visually inspect the ceramic burners through the observation window for blue flame/cracks, if cracks are present physically remove the burners, inspect and replace any and all damaged components or burners. WARNING: ensure the locking rods that hold the burner assembly in place is in the proper position and locked. Failure to properly position these rods can lead to personal injury, fire or death.
  1. If burners look good verify that the ionization wire connection is secure between the actual flame rod and the black connector between the transformer and igniter on the MCBA. Check for continuity between one end to the other of that wire. Remove and inspect the condition of the ionization rod, clean and/or replace as necessary. With the unit fired, verify that your ionization is at least 1—4uA.
  1. Verify that when the unit goes to fire that you have 24 VDC on the connector to the gas valve. If there is no voltage present, check the connection from the MCBA to the gas valve and verify voltage at the connector on the MCBA. If there is voltage at the MCBA but 0 VDC at the gas valve, check the wiring harness for continuity. If there is no voltage at the MCBA for the gas valve then replace the MCBA.

(1 0f 3) E-02