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Service Manual

Singular Combi Boiler - BTC 439002301 A (12.2021)

8.3     A4 Error (Overheating of Heat Exchanger) 

Error

Description

High Limit Cutout Error

 

T2: Stop the combustion when the surface temperature of the exhaust gas hood becomes higher than 302 °F due to 
backfi re.

 

T3: Stop the combustion when the surface temperature of the heat exchanger supply pipe becomes higher than 203 °F 
due to abnormal overheating.

(Operation principle: Bi-metal method, series connection)

Checkpoint

 

Check the connection of the overheat prevention device and wire connector.

 

—

Color: Red-Red

 

Check the connection of the high limit cutouts to the control board

 

Check the conduction condition of the high limit cutouts

 

Check if the High Limit Cutout HEX T2 (302°F) and High Limit Cutout Supply T3 (203°F) are normal

1) Check the temperature sensor resistance table
2) Check the scale on the detection part of the sensor

Table 26

Figure 13

Check the assembly condition 

of the control board and the 

high limit cutout connection.

Replace the high limit 

cutout connection

Replace the high limit 

cutout connection 

Replace the control board

Check the 

high limit cutout 

connection 

 

Is the 

resistance of 

the high limit cutout 

connection

normal? 

 

Yes

Yes

No

No

Separate the high limit cutout installed on

the heat exchanger(T2) and supply line (T3) 

from the control board and check

the resistance (Normal if it is below 1 Ω)

Summary of Contents for Singular 4000

Page 1: ...partment WARNING Improper installation adjustment alteration service or maintenance can cause property damage personal injury exposure to hazardous materials or loss of life Refer to the user s information manual provided with this boiler Installation and service must be performed by a qualified installer service agency or the gas supplier who must read and follow the supplied instructions before ...

Page 2: ...2 Service Manual Singular Combi Boiler BTC 439002301 A 12 2021 ...

Page 3: ...rror Abnormal Operation Gas Valve 29 8 8 A9 Error Exhaust Temperature Sensor Error 31 8 9 AA Error Overheating 33 8 10 ABError AbnormalOperation HeatExchangerTemperatureSensor 34 8 11 AC Error Abnormal Operation DHW Sensor 36 8 12 AD Error Clog of Condensate Trap 38 8 13 AE Error Blockage of Flue Pipe 40 8 14 EO Error Abnormal Operation Outdoor Temperature Sensor 42 8 15 E1 Error Abnormal Operatio...

Page 4: ...osed and out of the reach of children The boiler has a main burner flame that can come on at any time and will ignite flammable vapors Vapors cannot be seen and are heavier than air They can travel long distances along the ground and can be carried from other rooms to the boiler s main burner flame by air current WARNING SCALDHAZARD Water temperature over 125 F can cause severe burns or death from...

Page 5: ...operate or have access to the boiler WARNING IMPROPERORDANGEROUSOPERATION Immediately call a qualified service technician to inspect the appliance and replace any part of the control system and or any gas control which has been immersed in water WARNING This product can expose you to chemicals including Lead and Lead components which are known to the State of California to cause cancer and birth d...

Page 6: ...ctor Orifice Gas valve 3 way valve Pressure sensor Space heating supply Gas inlet Hot water outlet Burner hood Heat Exchanger Cover Pump Air vent Condensate drain Space heating return Cold water inlet Exhaust temperature sensor Flue connector Heating temperature sensor T2 Return temperature sensor DHW temperature sensor ...

Page 7: ...nition transformer Control Board TouchPad Secondary heat exchanger Primary heat exchanger Flow sensor Air Pressure Switch TDR damper Water Pressure Sensor Turbo fan assembly HighLimitCutout SupplyT3 203 F HighLimitCutout HEXT2 302 F CondensateTrap Flame rod Electrode assembly ...

Page 8: ... Hydronic DHW 12 30psi 15 150 psi Supply Pressure Natural Gas 3 5 10 5 WC Propane 8 13 WC Temperature Range Space Heating 82 F 180 F 27 C 82 C DHW 86 F 140 F 31 C 60 C Minimum Flow Rate DHW 0 5GPM 2 0LPM Power Supply Main Supply 120V AC 60 Hz uses less than 5 AMP Connection Sizes Space heating Supply Return 1 NPT Cold water Inlet 3 4 NPT Hot Water Outlet 3 4 NPT Gas Inlet 3 4 NPT Materials Primary...

Page 9: ...91 4 mm 2 7 68 6 mm 1 6 40 6 mm 6 1 154 9 mm 2 8 71 1 mm 3 4 86 4 mm 4 7 119 4 mm 2 2 55 9 mm 8 0 203 2 mm A B C D E F 1 8 45 7 mm 27 56 700 mm 31 87 809 5 mm Position Description Diameter A Space heating Return 1 NPT B Cold water inlet 3 4 NPT C Condensate Outlet 1 2 NPT D Hot water Outlet 3 4 NPT E Space heating Supply 1 NPT F Gas Inlet 3 4 NPT G Exhaust Vent 2 H Air inlet 2 Table 3 ...

Page 10: ...ture limit for exhaust gas OFF Temperature limit for exhaust gas EEP ROM data change switch ON Enable EEP ROM data change OFF Disable EEP ROM data change Long flue Length 1 DIP S W 3 DIP S W 4 FLUE LENGTH 2 PVC 3 PVC OFF OFF Up to 15 Up to 150 Long flue Length 2 OFF ON Up to 30 N A ON OFF Up to 45 ON ON Up to 60 N A N A Minimum heat capacity operation ON Minimum operation OFF Normal operation Maximu...

Page 11: ...ed White Black Brown Brown Blue Black Red Solenoid Valve T D R Damper Gas Valve Red Red Pressure Sensor Red Flow Detect Switch Black Purple White White High Limit Cutout Yellow Yellow Touch Pad 3 way Valve PUMP White White Green Green Blue Blue SRW Red SRW Red Condensate trap Blue Blue Green Red Gray Gray Black Black Black GND OPTION RCOP Brown Brown Outdoor Thermistor OPTION Domestic Hot Water Th...

Page 12: ...ction Check the circulation pump connection wire Voltage check Check range of voltage shown below Color Number of Wires BLACK WHITE ON AC 120 V OFF 0 V Table 5 7 2 Turn Down Ratio TDR Solenoid valve Part No 7738007264 Function To control the amount of mixed gas supplied with TDR of 10 1 It uses solenoid valve to control the amount of mixed gas Failure Event Solenoid valve not closing Solenoid valv...

Page 13: ...07262 Function Providing combustion air and gas To make the ideal combustion exhaust the flue gas before and after the combustion Failure Event Fan speed failure in case that the fan RPM is less than or equal to 600 RPM The fan assembly screw loosens or the fan is damaged Connection of the wire connector in fault Effects Unstable combustion condition Unit vibrating and making a noise The water hea...

Page 14: ...he cutout fails Effects Unable to stop combusting if the water temperature from the heat exchanger exceeds 203 F 95 C Error Code A4 Diagnostic Visual inspection Connection or breakage of wires Voltage check Check range of voltage shown below Color Number of Wires Red Red DC 5 V Table 10 7 8 Primary Heat Exchanger Part No 7738007256 Function Main part for heat transfer from the burner It has multip...

Page 15: ... of Wires N A Table 12 part number is for fully assembled heat exchanger unit 7 10 Sensor Part No 7738007297 Sensor Supply Return Sensor Heating Return Sensor DHW Exhaust Temperature Sensor Blue 7738007295 Sensor DHW 7738007268 Exhaust Temperature Sensor Function Measure the temperature of the hot water cold water exhaust gas in the boiler Failure Event Unable to properly measure the temperature i...

Page 16: ...ormal flame during the combustion Failure Event Fail to detect a flame in spite of the combustion process Improper gap Effects The boiler is not operated Error Code A6 A8 Diagnostic Visual inspection Connection or breakage of wires check the flame rod gap Check range of voltage shown below Color Number of Wires White Ground AC 24 V Table 15 7 13 Ignition Transformer Wire Part No 7738007252 Function...

Page 17: ...as Valve Part No 7738007270 Function Provide the gas for combustion For some reason it shuts off the gas valve automatically and prevents an unsafe condition due to combustion Failure Event Gas leak from the valve Unable to open close Effects Gas leak from the unit The unit does not operate Error Code A6 A8 Diagnostic Visual inspection Disconnection or breakage of wires Check range of voltage show...

Page 18: ...busting Failure Event Fail to drain condensation caused by clogged trap Condensation leakage into the unit Effects Stop combustion Condensation leakage Error Code AD Diagnostic Visual inspection Connection or breakage of wires check for physical damage to the trap body Voltage Check Check range of voltage shown below Color Number of Wires Green Red AC 24 V Table 21 7 19 Air Pressure Switch Part No...

Page 19: ...ection of the wire Check the fan wire for disconnection Check the PCB output voltage Red Black 0 45 V Yellow Black 0 13 V Table 23 Figure 5 Check the assembly condition of the control board and the fan connector Reassemble the control board and the fan connector Replace the control board Replace the fan Replace the fan Replace the control board Power ON faucet ON 1 GPM Check the fan input voltage ...

Page 20: ...ntrol board Input Voltage Check 1 Measure the control board input voltage measure while using the hot water Multi tester range DC V MeasurementMethod Measuredvalue Measure the applied voltage Red Black DC 5 45 V Yellow Black DC 10 13 V Measure FAN Hz White Yellow 0 270 Hz Table 24 Figure 8 V Applied Voltage Measurement Method Figure 9 Hz FAN Hz Measurement Method 2 If the voltage is measured norma...

Page 21: ...eckpoint Check the assembly of the pump connector Check the operation voltage of the pump Color White Black Check for any clogging of heating water pipes Table 25 Figure 10 Check the assembly of the control board and the pump connector and reassemble them Check the operation of the pump and the flow of heating water Replace the control board Replace the pump Power ON Operation Check for any cloggi...

Page 22: ... 12 2021 A3 Error Wire Check 1 Check the pump connector Figure 11 A3 Error Control Board Operation Voltage Check 1 Check the output voltage when the pump operation signal is activated Normal Normal if the voltage is higher than the input voltage Figure 12 V ...

Page 23: ...onnection of the high limit cutouts to the control board Check the conduction condition of the high limit cutouts Check if the High Limit Cutout HEX T2 302 F and High Limit Cutout Supply T3 203 F are normal 1 Check the temperature sensor resistance table 2 Check the scale on the detection part of the sensor Table 26 Figure 13 Check the assembly condition of the control board and the high limit cut...

Page 24: ...rror Wire Check 1 Check the connection status of the wire Figure 14 A4 Error High Limit Cutouts Check 1 Measure the resistance of the cutouts Normal 1 Ω or less Abnormal O L 2 If the resistance cannot be measured normally replace the high limit cutout Figure 15 Ω T2 T3 ...

Page 25: ...he pressure sensor Color Red Black DC 5 V Check the output voltage of the pressure sensor Color White Black Check the internal pressure in pipes Table 27 Figure 16 Check the assembly of the control board and the pressure sensor and reassemble them Fill the water Replace the control board Check the pipes Internal pressure in pipes 4 3PSI Check the pressure sensor input voltage Check for any pipe le...

Page 26: ...021 A5 Error Input Voltage of the Pressure Sensor Check 1 Check the pressure sensor for abnormalities in the input voltage Normal DC 5 V Figure 17 V A5 Error Pipe Pressure Check 1 Check for water leaks from the pipes and check the pressure of the expansion tank ...

Page 27: ...35 V Check the assembly and operation condition of the automatic igniter 1 Check the discharge state 2 Check the input voltage part of the automatic igniter Wire color Brown Brown AC 105 135 V Table 28 Figure 18 Replace the ignition transformer Replace the electrode assembly Replace the flame rod Check the 1st gas pressure Replace the gas valve Ignition miss Check the ignition transformer voltage ...

Page 28: ...ltage is not supplied normally replace the control board Figure 19 KΩ A6 Error Igniter Check 1 Check the gap of the igniter Gap 4 5 mm 2 Check the gap between the igniter and the burner Gap 8 10 mm A6 Error Ignition Transformer Check 1 First remove phillips screw on the ignition transformer and remove transformer for easier measurement of voltage Figure 20 2 Check the input voltage of the igniter ...

Page 29: ...cription Flame after combustion This error occurs if flame is detected after burner had shut off Checkpoint Check the operation condition of the gas valve Whether the flame rod is damaged or not Whether the flame rod comes into contact with the metal burner or not Table 29 Figure 24 Replace the control board Replace the flame rod Replace the gas valve Combustion stop Separate the flame rod wire and ...

Page 30: ...If the voltage is measured replace the control board Figure 25 V A8 Error Gas Valve Check 1 If flame is present when there is not a call for demand replace the gas valve Figure 26 A8 Error Flame Rod Check 1 Remove flame rod and check condition 2 Reassemble the flame rod turn on the power supply and measure the current Combustion condition Multi tester range µA Normal above 2 µA Connect the multi test...

Page 31: ...ature 104 F Combustion stopped Checkpoint Check if the heating water temperature is 43 F Check if the heating water sensor connection is OPEN Check the resistance of the heating water sensor Table 30 Figure 28 Check the assembly of the heating water sensor connector and reassemble it Replace the temperature sensor Operated when the heating water temperature is 42 F Is the temperature sensor resist...

Page 32: ... 2021 A9 Error Wire Check 1 Check if the heating water sensor connector is disconnected Figure 29 A9 Error Exhaust Temperature Sensor Check 1 Check if the heating water sensor is defective Defective OL Normal 86 F 40 kΩ 140 F 12 4 kΩ 185 F 3 9 kΩ Figure 30 kΩ ...

Page 33: ...od Measurement should be carried out after separating the sensor Table 31 Figure 31 An error occurs when the water temperature is 208 F 98 C or above Replace the temperature sensor Check the resistance of the temperature sensor Resistance 3 5 kΩ Yes No 86 F 40kΩ errorpossible 140 F 12 4kΩ 185 F 3 9kΩ Replace the control board AA Error T2 Temperature Resistance Check 1 Check if the resistance match...

Page 34: ... of the heating water sensor NTC method Separate the sensor and measure it at room temperature Check the heating water sensor for disconnection Check the heating water sensor for short circuit Figure 33 Figure 34 Check the assembly condition of the control board and the temperature sensor connector and reassemble the control board and the temperature sensor connector Replace the temperature sensor...

Page 35: ... 140 F 12 4 kΩ 185 F 3 9 kΩ Figure 37 KΩ AB Error Disconnection Check 1 Check if the heat exchanger overheat sensor is disconnected Disconnection OL Normal 86 F 40 kΩ 140 F 12 4 kΩ 185 F 3 9 kΩ Figure 38 kΩ AB Error Short Circuit Check 1 Check if the Heating water sensor has short circuited Short circuit 0 Ω Normal 86 F 40 kΩ 140 F 12 4 kΩ 185 F 3 9 kΩ Figure 39 Ω AB Error Control Board Check 1 If...

Page 36: ...e Hot Water DHW Sensor NTC method Separate the sensor and measure it at room temperature Check the DHW sensor for disconnection Check the DHW sensor for short circuit Figure 40 Figure 41 Check the assembly condition of the control board and the temperature sensor connector and reassemble the control board and the temperature sensor connector Replace the temperature sensor Replace the temperature s...

Page 37: ...onnection OL Normal 86 F 40 kΩ 140 F 12 4 kΩ 185 F 3 9 kΩ Figure 44 KΩ AC Error Disconnection Check 1 Check if the sensor is disconnected Disconnection OL Normal 86 F 40 kΩ 140 F 12 4 kΩ 185 F 3 9 kΩ Figure 45 kΩ AC Error Short Circuit Check 1 Check if the DHW sensor has short circuited Short circuit 0 Ω Normal 86 F 40 kΩ 140 F 12 4 kΩ 185 F 3 9 kΩ Figure 46 Ω AC Error Control Board Check 1 If the...

Page 38: ...logged by foreign material Checkpoint Check the connection short circuit of the wire connector Check if foreign material exists inside the condensation trap Check if the condensation water is frozen in the condensation hose Table 32 Figure 47 Clean the condensation trap Replace the control board Separate the control board and the condensation trap connector and re operate An error has occurred Yes...

Page 39: ... Check if the condensation trap is clogged 2 Separate the condensation trap and wash it with running water After washing the condensation trap fill the condensation trap with water up to 2 3 AD Error Freezing Burst Check 1 Check if the condensation water is frozen in the condensation hose 2 Melt the frozen condensation water with a tool if frozen AD Error Control Board Check 1 The condensation tra...

Page 40: ...eign material in the flue pipe or external factors of when the air pressure switch is defective Checkpoint Check the connection of the wire connector part 1 Control board and wire 2 Wind pressure S W and wire Check the air pressure switch for abnormality Check if there is foreign material in the flue pipe Table 33 Figure 50 Check and remove foreign material from the air inlet and outlet Replace the...

Page 41: ...3 Ω 2 Operate the water heater using hot water over 4GPM and check the air pressure switch for abnormalities when the fan spins at the maximum speed Normal 0 L Abnormal under 1Ω 3 Replace the air pressure switch if the resistance is abnormal AE Error Foreign Material Check 1 Check for any restrictions or blockage in the venting system Remove foreign material if present AE Error Control Board Check...

Page 42: ...emperature sensor wire Measure and check the resistance of the outdoor temperature sensor wire NTC method Check the outdoor temperature sensor for disconnection Check the outdoor temperature sensor for short circuit Table 34 Figure 54 Check the assembly condition of the control board and the temperature sensor wire Reassemble the control board and the temperature sensor wire Replace the temperatur...

Page 43: ...igure 56 Outdoor Air Sensor EO Error Disconnection Check 1 Check if the outdoor air sensor is disconnected Figure 57 kΩ EO Error Short Circuit Check 1 Check if the outdoor air sensor has short circuited Figure 58 Ω EO Error Control Board Check 1 If the wire connection and the resistance of the Hex Thermistor are normal replace the control board ...

Page 44: ...tance of the Exhaust Thermistor NTC method Separate the sensor and measure it at room temperature Check the Exhaust Thermistor for disconnection Check the Exhaust Thermistor for short circuit Table 35 Figure 59 Check the assembly condition of the control board and the temperature sensor connector and reassemble the control board and the temperature sensor connector Replace the temperature sensor R...

Page 45: ...al replace the Exhaust Temp Sensor Figure 62 KΩ E1 Error Disconnection Check 1 Check if the Exhaust Temp Sensor is disconnected Disconnection OL Normal 86 F 7 05 kΩ 140 F 2 5 kΩ 201 F 952 Ω Figure 63 kΩ E1 Error Short Circuit Check 1 Check if the Exhaust Temp Sensor has short circuited Short circuit 0 Ω Normal 86 F 7 05 kΩ 140 F 2 5 kΩ 201 F 952 Ω Figure 64 Ω E1 Error Control Board Check 1 If the ...

Page 46: ...ng abnormally over 208 F Checkpoint Exhaust temperature sensor error Wire color Blue Blue Control board control error Table 36 Figure 65 Replace the temperature sensor Replace the control board Check the assembly condition of the control board and the exhaust temperature sensor connector and reassemble the control board and the exhaust temperature sensor connector Exhaust gas temperature 158 F Res...

Page 47: ...al replace the Exhaust Temp Sensor Figure 68 KΩ E2 Error Disconnection Check 1 Check if the Exhaust Temp Sensor is disconnected Disconnection OL Normal 86 F 7 05 kΩ 140 F 2 5 kΩ 201 F 952 Ω Figure 69 kΩ E2 Error Short Circuit Check 1 Check if the Exhaust Temp Sensor has short circuited Short circuit 0 Ω Normal 86 F 7 05 kΩ 140 F 2 5 kΩ 201 F 952 Ω Figure 70 Ω E2 Error Control Board Check 1 If the ...

Page 48: ... the Return sensor NTC method Separate the sensor and measure it at room temperature Check the Return sensor for disconnection Check the Return sensor for short circuit Table 37 Figure 71 Check the assembly condition of the control board and the temperature sensor connector and reassemble the control board and the temperature sensor connector Replace the temperature sensor Replace the temperature ...

Page 49: ...tion OL Normal 86 F 40 kΩ 140 F 12 4 kΩ 185 F 3 9 kΩ Figure 74 KΩ E3 Error Disconnection Check 1 Check if the Hot Water Thermistor is disconnected Disconnection OL Normal 86 F 40 kΩ 140 F 12 4 kΩ 185 F 3 9 kΩ Figure 75 kΩ E3 Error Short Circuit Check 1 Check if the Return sensor has short circuited Short circuit 0 Ω Normal 86 F 40 kΩ 140 F 12 4 kΩ 185 F 3 9 kΩ Figure 76 Ω E3 Error Control Board Ch...

Page 50: ...Pressure sensor wire Measure the check the resistance of the pressure sensor NTC method Separate the sensor and measure it at room temperature Check the Pressure sensor for disconnection Check the Pressure sensor for short circuit Table 38 Figure 77 Check the assembly of the PCB and the mixing valve connector and reassemble them Assemble the pressure sensor wire Replace the pressure sensor Pressur...

Page 51: ...re Figure 78 Control Board Figure 79 Pressure Sensor E4 Error Pressure Sensor Check 1 Measure the resistance of the Pressure sensor 2 Check the pressure sensor input voltage at the control board Normal DC 5 V Abnormal 0 V 3 Replace the control board if the voltage output from the control board is abnormal Figure 80 V ...

Page 52: ...ption Overheating of temperature sensor Boiling superheat over 176 F An error is displayed when abnormal overheating caused by Hot water sensor Checkpoint Check the resistance of Temperature sensor NTC method Measurement should be carried out after separating the sensor Table 40 Figure 81 An error occurs when the water temperature is 176 F 80 C or below Replace the temperature sensor Check the res...

Page 53: ...lar Combi Boiler BTC 439002301 A 12 2021 EB Error Temperature Resistance Check 1 Check if the resistance matches the temperature on the following temperature resistance table 86 F 40 kΩ 140 F 12 4 kΩ 185 F 3 9 kΩ Figure 82 KΩ ...

Page 54: ...ut off the gas supply valve Figure 83 Gas 2 Pull out the power supply line Figure 84 3 Shut off the water valves for both the heating and DHW lines Figure 85 Pressure relief valv Space heating return Space heating supply Pressure relief valve Figure 86 Hot water Cold water 4 Loosen the 2 screws and open the case Figure 87 1 1 2 2 ...

Page 55: ...nd wire with the control board top screw together 9 3 Sensor Heating Return 1 Refer to 9 1 Preparation Step 2 Disconnect the temperature sensor terminal 3 Replace with a new temperature sensor Figure 89 9 4 Sensor DHW 1 Refer to 9 1 Preparation Step 2 Disconnect the temperature sensor terminal 3 Replace with a new temperature sensor Figure 90 9 5 Exhaust Temperature Sensor_T4 Blue 1 Refer to 9 1 P...

Page 56: ...xing screw Item 1 Figure 94 1 NG orifice shown LP orifice shown 5 After replacing with the new orifice refer to section 11 1 Combustion Analysis in the installation instructions 9 7 Air Pressure Switch 1 Refer to 9 1 Preparation Step 2 Separate the silicon hose from the air mixer 3 Loosen the air pressure switch fixing screws 2 each Item 3 and disconnect the green wire Figure 95 1 2 3 4 Replace with...

Page 57: ...minal Make sure to connect the wires completely 9 10 High Limit Cutout Supply T3 203 F 1 Refer to 9 1 Preparation Step 2 Disconnect the wire from the high limit cutout Item 2 3 Loosen the 1 high limit cutout fixing screw Item 3 Figure 98 1 2 4 Remove the high limit cutout bracket replace the high limit cutout with a new one and tighten the fixing screw 5 Connect the wires to the high limit cutout Co...

Page 58: ...er of gasket 1 electrode assembly 2 and bracket 3 as shown in the figure below Figure 101 2 3 1 9 13 Flame Rod 1 Refer to 9 1 Preparation Step 2 Separate the flame rod connection terminal Item 1 3 Separate the flame rod cap Item 2 4 Loosen the 3 fixing screws Item 3 Figure 102 1 2 3 5 Replace with a new flame rod 6 When replacing the flame rod use the new gasket and bracket that are provided with the ne...

Page 59: ...ad into the 4 grooves Item 3 marked on the figure below and push down Figure 106 2 3 3 3 3 9 15 Condensation Trap 1 Refer to 9 1 Preparation Step 2 Drain the water using the drain valve and water filter Item 2 Figure 107 1 3 Disconnect the wire from the condensation trap Item 2 4 Separate the condensation trap hose by lowering the clip Item 3 Figure 108 2 3 5 Loosen the condensation trap cap Item 4 ...

Page 60: ...3 fan fixing screws Item 1 Use the screwdriver for 2 screws use a wrench for the screw in the back Figure 112 1 5 Remove fan and silencer from boiler by pulling out silencer end first Figure 113 6 Separate the silencer part from the fan by removing two fixing screws Item 2 first Figure 114 2 7 Replace with a new fan When assembling a new unit for replacement assemble it in reverse order of separating ...

Page 61: ... 9 16 3 Separate the solenoid valve unit Item 2 by removing the 2 fixing screws Item 1 Figure 116 2 1 4 Replace with a new solenoid valve unit 5 After replacing it tighten the air mixer and the silencer fixing screws When replacing the solenoid valve unit pay attention to the the wire position When connecting the air mixer silencer assemble it along the solenoid wire groove as shown below Figure 117...

Page 62: ...ate the fan from the heat exchanger according to Section 9 16 4 Loosen fixing screw on bottom right hand side of heat exchanger cover and Remove heat exchanger cover and disconnect flame rod and electrode assembly wires Fig 120 Item 2 Figure 119 2 5 See Figure 121 Separate the fan connection terminal Item 1 solenoid valve terminal Item 2 overheat prevention device wire Item 3 and heat exchanger temp...

Page 63: ...New design does not have these screws Figure 124 11 Remove heat exchanger piping clips x2 and separate piping from heat exchanger Figure 125 Ensure gaskets remain in place with brass connector piping to the heat exchanger They will be necessary for reinstallation 12 Remove connecting clip and separate condensate hose from bottom of heat exchanger Figure 126 13 Remove two screws Item 2 on the right...

Page 64: ...2301 A 12 2021 14 Remove phillips screws on upper and lower heat exchanger bracket located on right and left side of the heat exchanger Fig 129 Figure 128 15 Remove heat exchanger fan from boiler 16 Install replacement heat exchanger in reverse order ...

Page 65: ...e circulation pump outlet and the space heating return line at the V1 valve 4 Connect one hose to the circulation pump inlet and place the free end in the bucket 5 Connect the other hose to the space heating supply line at the V2 valve and place the free end in the bucket 6 Pour approximately 4 gallons of virgin food grade white vinegar into the bucket 7 Open both valve V1 and V2 on space heating ...

Page 66: ...66 Service Manual Singular Combi Boiler BTC 439002301 A 12 2021 NOTES ...

Page 67: ... 67 Service Manual Singular Combi Boiler BTC 439002301 A 12 2021 NOTES ...

Page 68: ... 65 Grove St Watertown MA 02472 Tel 866 642 3198 Fax 603 965 7581 www bosch thermotechnology us BTC 439002301 A 12 2021 Bosch Thermotechnology Corp reserves the right to make changes without notice due to continuing engineering and technological advances ...

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