Viessmann Vitodens 200 Boilers
129 fault codes documented
Temperature display only in °C - Cannot change to °F
The boiler's temperature display unit only shows temperatures in Celsius (°C) and cannot be changed to Fahrenheit (°F), specifically when the programming unit is mounted remotely.
Fault 2 — No or low gas pressure detected
The boiler has detected a problem with the gas supply, specifically no or low gas pressure. This prevents the burner from igniting safely.
Fault 3 — No boiler water circulation detected
The boiler has detected that there is no boiler water circulation. This means water is not flowing properly through the heating system, which can cause overheating and prevent the boiler from operating.
Fault 5 — Flame failure during stabilization
The boiler has experienced a flame failure during the stabilization phase of ignition. This indicates that the flame ignited but could not be maintained or properly detected.
Fault 6 — Boiler temperature has exceeded monitoring limit
The boiler's internal temperature has exceeded its set monitoring limit. This is a safety shutdown to prevent damage from overheating.
Fault 06 or 07 - Insufficient air supply or vent blockage
These faults indicate that the boiler is not receiving enough fresh air for combustion, possibly due to blockages in the vent system or strong wind conditions.
Fault 8 — Flue gas temperature has exceeded monitoring limit
The flue gas temperature has exceeded its safety monitoring limit. This indicates a potential issue with the boiler's exhaust system or internal combustion, leading to dangerously high exhaust temperatures.
Fault 14 - Ignition failure or gas supply issue
This fault indicates a problem with the boiler's ignition process or issues with the gas supply, especially common in new propane installations or after extended periods of inactivity.
Fault 14 (Multiple Boilers) - One boiler locks out while others run
In a multi-boiler installation, one boiler enters lockout mode with a Fault 14 while others operate normally, suggesting an issue specific to that boiler's gas supply or ignition under high demand.
Fault 29 — Open circuit at power pump module terminals 1 and L
An open circuit has been detected at terminals 1 and L on the Multi terminal of the power pump module. This indicates a wiring issue or a problem with safety equipment connected to these terminals.
Fault 30 (Detailed 140) — Burner blocked due to boiler water sensor short circuit
The boiler's burner is blocked because there is a short circuit detected in the boiler water temperature sensor. This sensor helps the boiler regulate temperature, and a short circuit means it's not reading correctly.
Fault 33 — Power supply voltage below minimal level or internal fuse failure
The boiler's power supply voltage is below the minimum operating level, or an internal fuse has failed. This prevents the boiler from receiving adequate power to function.
Fault 38 (Detailed 140) — Burner blocked due to boiler water sensor cable broken
The boiler's burner is blocked because the cable for the boiler water temperature sensor is broken. A damaged cable prevents the sensor from sending correct temperature readings to the boiler's control unit.
Fault A1 - Boiler communication issue
This fault indicates a general communication problem within the boiler system. It requires resetting the boiler and potentially checking internal circuit boards.
Fault A3 - Bus communication problem with Cascade Control
This fault indicates a bus communication problem, specifically with the Cascade Control system, which manages multiple boilers.
Fault A4 - Incorrect coding address
This fault indicates that a specific coding address (0B8:006) might have an incorrect value, affecting boiler operation.
Fault B0 (Detailed 141) — Burner blocked due to flue gas sensor short circuit
The boiler's burner is blocked because a short circuit has been detected in the flue gas temperature sensor. This sensor monitors the temperature of exhaust gases, and a short circuit can lead to incorrect readings.
Fault B1 - No boiler temperature display or menu access
The boiler displays a B1 fault code, which results in the boiler temperature not being displayed and inability to access system menus or installer setup. This indicates an issue with the programming unit or its connection.
Fault B8 (Detailed 141) — Burner blocked due to flue gas sensor cable broken
The boiler's burner is blocked because the cable connected to the flue gas temperature sensor is broken. This prevents the boiler from accurately monitoring flue gas temperatures, causing a safety shutdown.
"Boiler enabling" on display - Boiler is starting up or has a coding issue
The display shows "Boiler enabling," which indicates the boiler is initiating operation, but it can also signify that certain critical coding addresses might have been altered from their factory default settings.
Cannot Change Date - Date setting issue
The user is unable to change the date setting on the boiler's control, which typically indicates a specific coding address needs adjustment.
Fault CC - Boiler lockout with red light
The boiler enters a lockout mode, indicated by a red light, and displays fault code CC. This suggests an issue with the LGM (burner control unit).
Connection error and triangle symbol — Problem with connection to programming unit
The display shows a 'Connection error' message along with a triangle symbol, indicating an issue with the cable or plug connecting the heat management unit (HMU) and the programming unit (HMI).
Dashes on display - Coding values not shown or system address missing
The boiler display shows dashes instead of coding values (e.g., "000---") and system addresses (000:, 0B8:) are not displayed when trying to access coding level 2. This suggests a wiring or communication problem with accessories or the programming unit.
Fault E1 (Detailed 202) — Burner fault: ionization current too high
The burner is in fault mode because the ionization current detected during calibration is too high. This current is crucial for detecting the flame, and an incorrect reading indicates a combustion issue.
Fault E2 (Detailed 201) — Burner fault: low heating water flow rate
The burner is in fault mode because the heating water flow rate is too low during calibration. Insufficient water flow can lead to overheating and prevent the boiler from operating correctly.
Fault E3 (Detailed 204) — Burner fault: low heat transfer or temperature limiter shutdown
The burner is in fault mode because heat transfer is too low during calibration, or the temperature limiter has activated and caused a shutdown. This indicates the boiler is not effectively transferring heat or has reached a critical temperature.
Fault E5 (Detailed 226) — Burner blocked: faulty flame amplifier
The burner is blocked due to a fault with the flame amplifier. The flame amplifier is a crucial component for detecting and confirming the presence of a flame, and a fault here prevents the boiler from operating safely.
Fault E7 (Detailed 192) — Burner fault: ionization current too low
The burner is in fault mode because the ionization current detected during calibration is too low. A low ionization current can mean the flame is not strong enough or not being properly detected.
Fault E8 (Detailed 189) — Burner fault: ionization current outside permissible range
The burner is in fault mode because the ionization current is outside the acceptable operating range. This could indicate issues with the gas supply, the gas type, or the ionization electrode itself.
Fault EA (Detailed 193) — Burner fault: ionization current deviation too great
The burner is in fault mode because the ionization current measured during calibration shows a significant deviation from its previous normal level. This indicates an unstable or inconsistent flame detection.
Fault EB (Detailed 194) — Burner fault: repeated flame loss during calibration
The burner is in fault mode because it repeatedly loses the flame during the calibration process. This suggests an instability in the combustion process or issues with flame detection.
Fault EC (Detailed 67 or 195) — Burner fault: parameter fault during calibration
The burner is in fault mode due to a parameter fault that occurred during calibration. This indicates an issue with the boiler's internal settings or configuration while trying to optimize its operation.
Fault ED (Detailed 191) — Burner fault: internal fault
The burner is in fault mode due to an internal fault within the boiler's control system. This is a general error indicating a problem with the boiler's internal electronics or software.
Fault EE (Detailed 132) — Burner fault: missing or weak flame signal at start
The burner is in fault mode because there is no flame signal or a very weak flame signal detected when the burner attempts to start. This prevents the boiler from igniting safely.
Fault EF (Detailed 138) — Burner fault: flame lost immediately after ignition
The burner is in fault mode because the flame is lost almost immediately after it has successfully ignited, during the safety time. This indicates an instability or failure to maintain combustion.
"EXT. program 2" on screen - External program detected
The display shows "EXT. program 2," typically appearing during startup, indicating an external program or a communication issue with the boiler's control system.
F.70 — Burner in fault state due to internal control unit error
The burner is in a fault state due to an internal error within the burner control unit. This critical error will prevent the boiler from operating.
F.71 — Burner in fault state: Fan speed too low
The burner is in a fault state because the fan speed is too low. This can indicate a physical obstruction or an incorrect setting.
F.72 — Burner in fault state: Fan idle state not reached
The burner is in a fault state because the fan unit did not reach its idle state. This can prevent the boiler from operating safely.
F.73 — Burner in fault state due to internal communication error
The burner is in a fault state due to an internal communication error. This suggests a problem within the boiler's control system.
F.74 — Burner locked out (Water pressure too low)
The burner is locked out, and there is no central heating or domestic hot water heating because the water pressure in the system is too low. This is a common issue that can often be resolved by topping up the system.
F.77 — Burner in fault state due to data memory error
The burner is in a fault state due to an error in the data memory of the burner control unit. This can prevent the boiler from operating correctly.
F.89 — No heating or hot water: Internal circulation pump blocked
There is no central heating or domestic hot water (DHW) heating because the internal circulation pump is blocked. This prevents water from circulating in the system.
F.91 — Function of affected extension in emergency mode (DIO electronics module communication error)
An affected extension is operating in emergency mode due to a communication error with the DIO electronics module. This means a component is not communicating correctly with the main unit.
F.92 — Function of the relevant electronics module in emergency mode (ADIO electronics module communication error)
A relevant electronics module is operating in emergency mode due to a communication error with the ADIO electronics module. This could be due to incorrect settings, wiring issues, or voltage problems.
F.94 — Electronics modules connected to PlusBus not functioning (Voltage error PlusBus)
Electronics modules connected to the PlusBus are not functioning due to a voltage error on the PlusBus. This could be caused by too many devices connected or a short circuit in the wiring.
F.100 — Electronics modules connected to PlusBus not functioning (Voltage error PlusBus)
Electronics modules connected to the PlusBus are not functioning due to a voltage error on the PlusBus. This could be caused by too many devices connected or a short circuit in the wiring.
F.104 — External fault message input active
An external fault message input is active, depending on the configuration of the EM EA1 extension (DIO electronics module). This indicates an issue with a connected external device.
F.142 — Burner in fault state due to CAN bus communication error
The burner is in a fault state because of a communication error on the CAN bus. This indicates a problem with how different components are communicating.
F.160 — Burner in a fault state (Communication error CAN bus)
The burner is in a fault state due to a communication error on the CAN bus, which means internal components are not communicating correctly. This could involve internal or external CAN bus connections.
F.161 — Burner in a fault state (BCU data memory access error)
The burner is in a fault state indicating an error accessing the data memory of the Burner Control Unit (BCU). This can prevent the burner from storing or retrieving necessary operational data.
F.163 — Burner in a fault state (Memory access checksum error BCU)
The burner is in a fault state indicating a checksum error during memory access in the Burner Control Unit (BCU). This points to an issue with the integrity of data storage.
F.180 — Burner in a fault state (Gas pressure too low)
The burner is in a fault state because the gas pressure is too low, which prevents proper combustion. This can be due to issues with your gas supply or the gas pressure switch.
F.182 — No DHW heating (Short circuit, outlet temperature sensor)
There is no domestic hot water heating because a short circuit has been detected in the outlet temperature sensor (if installed). This sensor measures the temperature of the hot water.
F.183 — No DHW heating (Lead break, outlet temperature sensor)
There is no domestic hot water heating because a lead break (broken wire) has been detected in the outlet temperature sensor (if installed). This prevents the sensor from sending correct temperature readings.
F.184 — Burner in a fault state (Short circuit, common supply temperature sensor/high limit safety cutout)
The burner is in a fault state due to a short circuit in the common supply temperature sensor or the high limit safety cutout. This is a critical safety and operational component.
F.185 — Burner in a fault state (Lead break, common supply temperature sensor/high limit safety cutout)
The burner is in a fault state due to a lead break (broken wire) in the common supply temperature sensor or the high limit safety cutout. This prevents critical temperature readings and safety functions.
F.299 — Time/date incorrect (Real time clock setting incorrect)
The appliance display shows an incorrect time or date, indicating an issue with the real time clock setting. This can affect scheduled operations.
F.342 — No central heating, no DHW heating (Communication error, BCU burner control unit)
There is no central heating or domestic hot water due to a communication error with the Burner Control Unit (BCU). This indicates an issue with connections or the internal CAN bus.
F.346 — Burner in fault state: Ionization current calibration error
The burner is in a fault state due to an ionization current calibration error. This affects the boiler's ability to accurately detect and maintain a flame.
F.348 — Burner in fault state: Gas modulation valve issue
The burner is in a fault state related to the gas modulation valve. This may occur in systems with multiple boilers or indicate a flue issue.
F.349 — Burner in fault state: Air mass flow rate not correctly detected
The burner is in a fault state because the air mass flow rate is not being detected correctly in the fan unit. This indicates an issue with airflow measurement or components.
F.350, F.351 — Burner in fault state: Ionization current outside permissible range
The burner is in a fault state because the ionization current is outside the permissible range. This indicates an issue with flame detection and safety.
F.352 — Burner in fault state: CO limit exceeded
The burner is in a fault state because the CO (carbon monoxide) limit within the boiler has been exceeded. This is a critical safety issue indicating improper combustion or flue problems.
F.353 — Burner shutdown: Insufficient gas supply, reduced output
The burner has shut down (with potential for restart if demand exists) due to an insufficient gas supply, leading to reduced burner output. This means the boiler isn't getting enough fuel.
F.354 — Burner in fault state: Gas modulation valve tolerance exceeded
The burner is in a fault state because the gas modulation valve tolerance is outside the permissible range. This affects gas flow control and combustion.
F.355 — Burner in fault state: Flame signal present at burner start
The burner is in a fault state because a flame signal was already present at the burner start (analogue signal reference check). This is a safety issue preventing normal ignition.
F.357 — Burner in fault state: Insufficient gas supply
The burner is in a fault state due to an insufficient gas supply. This can be caused by various issues from the gas shut-off valve to the gas line itself.
F.372 — Burner in a fault state (Repeated flame loss during calibration)
The burner repeatedly loses its flame during the calibration process, which can prevent it from operating correctly. This may be due to electrode issues, flue system problems, or gas solenoid valve contamination.
F.373 — Burner in a fault state (Heat transfer too low during calibration)
The burner is in an error state because the heat transfer is too low during calibration, possibly due to the temperature limiter shutting down or issues with the circulation pump or diverter valve.
F.377 — Burner in fault state: Ionization adjustment stabilization not met
The burner is in a fault state because the stabilization conditions for post-calibration of the ionization adjustment were not met. This can be due to incorrect gas type settings.
F.378 — Burner in a fault state (Flame loss during stabilization or operating phase)
The burner is experiencing flame loss either during the stabilization period or while operating. This can be caused by gas supply issues, flue gas recirculation, or contamination.
F.379 — Burner in a fault state (Flame signal not present or insufficient)
The burner is in an error state because the flame signal is either absent or too weak, which means the appliance cannot detect a flame, crucial for safe operation.
F.380 — Burner in a fault state (Flame loss immediately after flame formation)
The burner loses its flame immediately after it has formed, during the safety time. This can be due to gas supply issues, flue gas problems, or issues with the ionization electrode.
F.381 — Burner in fault state: Flame loss during operation phase
The burner is in a fault state due to a flame loss during its normal operating phase. This indicates a sustained issue with flame stability.
F.382 — Burner in fault state: Error counter limit exceeded
The burner is in a fault state because an internal error counter has exceeded its limit. This usually means multiple minor faults have occurred, indicating an underlying problem.
F.383, F.384 — Burner in fault state: Possible gas line contamination
The burner is in a fault state, possibly due to contamination in the gas line. This affects the boiler's ability to receive a clean and steady gas supply.
F.385 — Burner in fault state: Short circuit in ionization current signal
The burner is in a fault state due to a short circuit in the ionization current signal. This can also indicate a problem with the BCU burner control unit.
F.386 — Burner in a fault state (BCU burner control unit faulty)
The burner is in an error state because the Burner Control Unit (BCU) is faulty. This unit is essential for managing the burner's operation.
F.387 — Burner in fault state: Ground fault in ionization current
The burner is in a fault state due to a ground fault in the ionization current, or a faulty BCU burner control unit. Condensate backup can also cause this issue.
F.388 — Burner in a fault state (BCU burner control unit faulty)
The burner is in an error state because the Burner Control Unit (BCU) is faulty. This unit is essential for managing the burner's operation.
F.395 — Burner in a fault state (IO electrode ground fault or BCU burner control unit faulty)
The burner is in an error state, potentially caused by a ground fault in the IO electrode or a problem with the Burner Control Unit (BCU).
F.396 — Burner in a fault state (BCU burner control unit faulty)
The burner is in an error state because the Burner Control Unit (BCU) is faulty. This unit is essential for managing the burner's operation.
F.399 — Burner in a fault state (IO electrode ground fault or BCU burner control unit faulty)
The burner is in an error state, potentially caused by a ground fault in the IO electrode or a problem with the Burner Control Unit (BCU).
F.400 — Burner in fault state due to control unit error
The burner is in a fault state because the BCU burner control unit is faulty. This error will stop the boiler from operating.
F.401 — Burner in a fault state (IO electrode ground fault or BCU burner control unit faulty)
The burner is in an error state, potentially caused by a ground fault in the IO electrode or a problem with the Burner Control Unit (BCU).
F.402 — Burner in a fault state (BCU burner control unit faulty)
The burner is in an error state because the Burner Control Unit (BCU) is faulty. This unit is essential for managing the burner's operation.
F.403 — Burner in a fault state (Ionization electrode ground fault or BCU burner control unit faulty)
The burner is in an error state, potentially caused by a ground fault in the ionization electrode or a problem with the Burner Control Unit (BCU).
F.404 — Burner in fault state due to control unit error
The burner is in a fault state because the BCU burner control unit is faulty. This error prevents the boiler from starting or operating.
F.405 — Burner in a fault state (Ionization electrode ground fault or BCU burner control unit faulty)
The burner is in an error state, potentially caused by a ground fault in the ionization electrode or a problem with the Burner Control Unit (BCU).
F.406, F.408, F.410 — Burner in fault state due to control unit error
The burner is in a fault state because the BCU burner control unit is faulty. These errors will prevent the boiler from running.
F.416 — Burner locked out due to flue gas temperature sensor positioning
The burner is locked out because the flue gas temperature sensor is incorrectly positioned. This is a safety measure to prevent improper operation.
F.417, F.418 — Burner in a fault state (BCU burner control unit faulty)
The burner is in an error state because the Burner Control Unit (BCU) is faulty. This unit is essential for managing the burner's operation.
F.425 — Time synchronization failed, normal operation with calculation error
The system is operating normally, but a calculation function is not working because time synchronization failed. This may affect scheduling or data logging.
F.430 — Normal operation; Communication error gateway
The system is operating normally, but there's a communication error with the gateway module. This can affect how the boiler communicates with other parts of the system.
F.446 — Burner in a fault state (Deviation, boiler supply temperature sensor/high limit safety cutout)
The burner is in an error state due to a deviation detected in the boiler's supply temperature sensor or the high limit safety cutout. This could mean a sensor is providing incorrect readings.
F.447, F.448 — Burner in fault state: Deviation in ionization current signal
The burner is in a fault state due to a deviation in the ionization current signal. This indicates a problem with how the boiler detects the flame.
F.449, F.450, F.451, F.452 — Burner in a fault state (Error in scheduled program run monitoring)
The burner is in a fault state due to an error detected in the scheduled program run monitoring. This suggests an issue with the burner's internal program execution.
F.453 — Burner in fault state: Synchronization error in sequence
The burner is in a fault state due to a synchronization error in its operational sequence. This indicates a timing or coordination problem within the boiler's control system.
F.454 — Burner in a fault state (Incorrect BCU software version)
The burner is in an error state because the Burner Control Unit (BCU) has an incorrect software version, which can prevent proper operation.
F.455 — Burner in fault state: Error in program run monitoring
The burner is in a fault state due to an error in the program run monitoring. This indicates a general problem with the boiler's internal programming or operation.
F.455, F.456 — Burner in a fault state (Error in program run monitoring)
The burner is in a fault state due to an error detected in the program run monitoring. This suggests an issue with the burner's internal program execution.
F.456 — Burner in fault state: Error in program run monitoring with fan issue
The burner is in a fault state due to an error in program run monitoring, potentially linked to a sluggish or blocked fan. This affects combustion and safe operation.
F.457 — Burner in fault state: Fan sluggish or blocked
The burner is in a fault state because the fan is sluggish or blocked. This issue can prevent proper airflow for combustion, leading to boiler shutdown.
F.458 — Burner in a fault state (Faulty reset sequence)
The burner is in an error state due to a faulty or safety-relevant reset sequence, meaning the system cannot correctly reset itself after an issue.
F.463 — Burner in fault state: Contaminated combustion air or flue gas recirculation
The burner is in a fault state due to contaminated combustion air or flue gas recirculation. Foreign bodies or deposits can interfere with the combustion process.
F.464 — Burner in fault state: Low ionization current during calibration
The burner is in a fault state because the ionization current was too low during calibration, or the reading was implausible. This can affect flame detection and safety.
F.467 - Burner in a fault state due to insufficient gas supply
The boiler's burner has entered a fault state because the gas supply was not sufficient during calibration. This can be caused by problems with the gas line or internal components being contaminated.
F.468 - Burner in a fault state due to high ionization current
The boiler's burner has entered a fault state because the ionization current was too high during calibration. This can be caused by issues with the ionization electrode, or excessive dust in the ventilation air leading to deposits.
F.471 - No call for heat due to lead break or short circuit
The boiler is not receiving a call for heat, indicating a problem with a sensor or its connection. This is often caused by a broken wire or a short circuit in the system.
F.473 - Heat Management Unit (HMU) communication error
There is a communication error between the BCU burner control unit and the HMU heat management unit. This usually points to a problem with the connecting cable between these two components.
Fault F1 (Detailed 135) — Burner fault: flue gas temperature exceeded limit
The burner is in fault mode because the maximum flue gas temperature limit of 230°F (110°C) has been exceeded. This is a critical safety shutdown indicating potential overheating or restricted exhaust.
Fault F2 (Detailed 129) — Burner fault: fixed high limit switch open
The burner is in fault mode because the fixed high limit switch has opened (activated). This safety switch trips when the boiler's internal temperature becomes excessively high, preventing damage.
Fault F3 - Low-loss header sensor or accessory issue
This fault suggests a problem with the connections or wiring to the low-loss header sensor of the Cascade Control, or an issue with other accessories like the outdoor temperature sensor.
Fault F4 - Air in the system causing pump racing
The boiler exhibits an F4 fault, often accompanied by the pump racing and high-temperature spikes, indicating air trapped within the heating system. This can lead to fault 02 (fixed high limit switch).
Fault F8 (Detailed 148) — Burner fault: gas valve closes too late
The burner is in fault mode because the gas valve closes too late. This is a critical safety fault as it means gas flow is not being cut off promptly, which can lead to unsafe gas accumulation.
Fault F9 (Detailed 151 or 152) — Burner fault: fan speed too low during start
The burner is in fault mode because the fan speed is too low during the burner start sequence. The fan is essential for proper combustion air supply and flue gas exhaust, so low speed prevents safe operation.
Fault FA (Detailed 154) — Burner fault: fan not at standstill
The burner is in fault mode because the fan is not at a standstill when it should be. This can indicate a stuck fan or a control issue, preventing the boiler from starting or operating safely.
Fault FC (Detailed 190) — Burner fault: faulty gas valve or blocked vent system
The burner is in fault mode because either the gas valve is faulty, there's an issue with the modulation valve control, or the vent system is blocked. This impacts gas supply and exhaust, preventing safe operation.
Fault FD (Detailed 227) — Burner fault: boiler coding card missing (B7 displayed)
The burner is in a fault state, and an additional fault B7 is displayed, indicating that the boiler coding card is missing. This card contains essential operational parameters for the boiler.
Fault FE (Detailed 158, 159, 162 or 225) — Burner fault: damaged or incorrect boiler coding card/main PCB
The burner is in fault mode due to a damaged or incorrect boiler coding card, or an issue with the main PCB (Printed Circuit Board). These components are critical for the boiler's control and operation.
Fault FF (Detailed 224) — Burner fault: internal fault or stuck reset button
The burner is in fault mode due to an internal fault or because the reset button R is blocked. This indicates a problem with the boiler's internal electronics or a physical issue with the reset mechanism.
Ice buildup on vent - Extreme low temperatures
Extreme low temperatures can cause ice to build up on the side wall or vertical venting termination, potentially obstructing the boiler's exhaust or air intake.
Incorrect Coding 015 - Boiler firing without circulation pump or DHW pump not energized
Changing coding address 015 from its factory default can cause significant operational problems. For models 6-24C/6-24/8-32, changing to 015:001 results in the boiler firing without the circulation pump and solenoid valve. For models 11-44/15-60, changing to 015:000 results in the DHW pump not being energized. This may also lead to fault 02.
Incorrect Coding 017 - Burner firing without circulation pump
Modifying coding address 017 from its factory default (017:001) for models 6-24/8-32 will cause the burner to fire without the circulation pump operating, potentially leading to fault 02. This coding has no effect on models WB2-44/60.
Not enough flow through boiler - Undersized pump
The boiler experiences insufficient water flow, particularly in models 11-44/15-60, often due to an undersized circulation pump.
Boiler does not ramp up to high fire - Blocked gas valve screen
The boiler, especially in multiple boiler systems with cascade control, fails to ramp up to its high fire setting, indicating a potential blockage in the gas supply.
Outdoor Temperature Sensor Fault - Incorrect temperature readings
The boiler is detecting an issue with the outdoor temperature sensor, which can lead to incorrect heating control based on external conditions.