Biasi Boiler Error Codes: Causes & Fixes
The most common Biasi boiler error codes are generally linked to low system pressure, ignition or flame problems, overheating, circulation issues and faults with sensors or other boiler components. Some problems can be checked safely at home, while others will require a qualified Gas Safe engineer.
The exact meaning of a fault code can vary depending on the Biasi boiler model, which is why it is always worth checking your boiler’s manual if the code displayed on your boiler is different from those covered below.
However, this guide covers the commonly encountered Biasi fault codes and explains what they mean, what may have caused them and what you can do next.
Biasi Boiler Codes: A Quick Overview
The table below provides a quick overview of common Biasi boiler codes and what each code generally means before we look at the possible causes and fixes in more detail.
| Biasi Boiler Error Code | What It Generally Means |
| ER 01 / E01 | Ignition or flame failure |
| ER 02 / E02 | Boiler safety thermostat or overheating fault |
| ER 03 / E03 | Flue, fan or air pressure problem |
| ER 04 / E04 | Low boiler water pressure |
| ER 05 / E05 | Central heating temperature sensor fault |
| ER 06 / E06 | Hot water temperature sensor fault |
| ER 07 / E07 | Temperature sensor or control-related fault |
| ER 10 / E10 | System pressure or water circulation issue |
| ER 12 / E12 | Hot water or diverter valve-related problem |
| ER 16 / E16 | Fan, electrical or boiler component fault |
| ER 25 / E25 | Boiler overheating or poor water circulation |
| ER 28 / E28 | Hot water flow or temperature control problem |
| ER 32 / E32 | Temperature sensor or electrical connection fault |
| ER 36 / E36 | Gas supply, ignition or flame detection problem |
| ER 40 / E40 | Central heating sensor fault |
| ER 41 / E41 | Boiler temperature sensor fault |
| ER 42 / E42 | Sensor or boiler control fault |
Important: Biasi has produced a range of boiler models over the years, including combi, system and regular boilers. Fault code meanings can differ between models, so use this guide as a general reference and check your boiler manual where possible.
Biasi Boiler Codes: Causes & How To Fix
The following Biasi boiler codes can help you identify whether the problem is something simple, such as low pressure, or whether you need to arrange a professional boiler repair.
ER 01 / E01: Ignition Or Flame Failure
The ER 01 or E01 error codes usually means that the boiler has attempted to ignite but has not successfully detected a flame.
For your boiler to provide heating and hot water, the burner needs to ignite successfully. If this process fails, the boiler will normally shut down as a safety measure.
Possible causes include:
- A temporary interruption to the gas supply
- The gas supply being switched off
- An issue with the boiler’s ignition system
- A faulty flame sensor
- A problem with the gas valve
- A fault with the boiler’s internal components
How To Fix ER 01 / E01
- Check whether you have a gas supply. If other gas appliances in your home are also not working, there may be an issue with your gas supply.
- Check that the boiler’s gas isolation valve is open. Do not attempt to interfere with gas components.
- Reset the boiler once. Follow the reset instructions in your Biasi boiler manual.
- Wait to see if the boiler restarts normally.
- Contact a Gas Safe registered engineer if the code returns.
Do not repeatedly reset a boiler that continues to display an ignition fault. If there is a problem with the ignition system, gas valve or flame detection, the boiler should be inspected by a qualified engineer.
For homeowners and landlords, unexpected ignition faults are a good example of why a boiler cover plan can be useful. Depending on the level of cover you choose, having protection in place can help you avoid facing the full cost of an unexpected boiler repair.
ER 02 / E02: Boiler Overheating Fault
The ER 02 or E02 fault codes generally indicate that the boiler has become too hot or that its safety thermostat has detected an overheating condition.
Your boiler contains safety controls designed to switch it off if temperatures become too high. This helps protect the boiler from damage.
Common causes include:
- Poor water circulation
- A faulty pump
- A blockage within the heating system
- Air trapped in radiators or pipework
- A faulty temperature sensor
- A problem with the boiler’s heat exchanger
How To Fix ER 02 / E02
- Turn the boiler off and allow it to cool down.
- Check the boiler pressure. Low pressure can contribute to circulation problems.
- Check whether your radiators are heating unevenly. Cold areas may indicate trapped air or circulation problems.
- Reset the boiler once it has cooled down, following the manufacturer’s instructions.
- Contact a Gas Safe engineer if the code returns.
Do not remove the boiler casing or attempt to repair internal components yourself. Overheating can sometimes point to a more serious circulation or component fault.
ER 03 / E03: Flue, Fan Or Air Pressure Fault
The ER 03 or E03 error codes usually relates to a problem with the boiler’s fan, flue system or air pressure monitoring.
Modern gas boilers need to remove combustion gases safely from your property. If the boiler detects that this process is not working correctly, it may shut down.
Possible causes include:
- A fault with the boiler fan
- A blocked or obstructed flue
- A problem with the air pressure switch
- Damaged electrical connections
- A fault within the boiler’s control system
How To Fix ER 03 / E03
- Check whether there is any obvious external obstruction around the flue outlet. Do not dismantle or interfere with the flue.
- Reset the boiler once.
- If the code returns, switch the boiler off.
- Arrange for a Gas Safe registered engineer to inspect the boiler.
Flue and combustion-related faults should not be treated as DIY repairs. A qualified engineer will need to check the fan, flue system and associated safety components.
ER 04 / E04: Low Boiler Water Pressure
The ER 04 or E04 error codes commonly indicate that the pressure within the central heating system is too low.
Most sealed heating systems need to maintain the correct pressure to allow water to circulate properly through the boiler, radiators and pipework. If the pressure drops too low, the boiler may stop working.
Low boiler pressure may be caused by:
- A small leak within the heating system
- A radiator valve leak
- A leak from pipework
- A pressure relief valve releasing water
- Recent radiator bleeding
- A gradual loss of pressure over time
How To Fix ER 04 / E04
- Check the boiler pressure gauge or display.
- If the pressure is low, refer to your Biasi boiler manual for the correct repressurising procedure.
- Use the filling loop or filling system only if you are confident that you know how to use it safely.
- Increase the pressure to the recommended level for your boiler.
- Close the filling loop correctly.
- Reset the boiler if required.
- Monitor the pressure over the next few days.
If the pressure continues to drop, there may be a leak or another fault that needs professional attention.
A boiler cover plan can be particularly useful when recurring problems develop. Instead of waiting until a fault becomes more serious, having cover in place can give you a route to professional help when your boiler develops an unexpected problem.
ER 05 / E05: Central Heating Temperature Sensor Fault
The ER 05 or E05 codes generally indicate a fault with the sensor that monitors the temperature of the central heating system.
The boiler relies on temperature sensors to control how much heat it produces. If a sensor sends incorrect information or stops communicating with the boiler, the system may shut down to prevent damage.
Possible causes include:
- A faulty temperature sensor
- Loose or damaged wiring
- A poor electrical connection
- A fault with the boiler’s control board
How To Fix ER 05 / E05
- Try resetting the boiler once.
- Check whether the fault clears temporarily.
- Do not remove the boiler casing to inspect the sensor or wiring.
- Arrange for a Gas Safe registered engineer to diagnose the fault if the code remains or returns.
A sensor replacement may be relatively straightforward for a qualified engineer, but the exact cause should be identified before any parts are replaced.
ER 06 / E06: Hot Water Temperature Sensor Fault
The ER 06 or E06 fault codes generally relate to the sensor responsible for monitoring your domestic hot water temperature.
If this sensor is not working correctly, the boiler may struggle to control the temperature of the hot water coming from your taps and showers.
Common causes include:
- A faulty hot water sensor
- Damaged wiring
- Loose electrical connections
- A boiler control fault
How To Fix ER 06 / E06
- Reset the boiler once.
- Check whether the boiler begins operating normally.
- If the fault code remains, avoid repeatedly resetting the boiler.
- Contact a qualified Gas Safe engineer to inspect the sensor and related components.
If you are receiving inconsistent hot water temperatures, this may also be a sign that the underlying issue has developed gradually.
ER 07 / E07: Temperature Sensor Or Control Fault
The ER 07 or E07 error codes can indicate a problem involving a temperature sensor or the way the boiler is receiving information from one of its control components.
Because the exact meaning can depend on the Biasi boiler model, checking the boiler manual is particularly important for this code.
Possible causes may include:
- A faulty sensor
- Wiring problems
- A poor electrical connection
- A control board fault
How To Fix ER 07 / E07
- Take note of the exact code shown on the display.
- Check your boiler manual for the model-specific meaning.
- Reset the boiler once if the manufacturer recommends doing so.
- Contact a qualified engineer if the code remains.
Providing the exact Biasi boiler model and fault code when booking a repair can help the engineer prepare for the visit.
ER 10 / E10: System Pressure Or Water Circulation Problem
The ER 10 or E10 codes can be linked to a pressure problem or an issue affecting the circulation of water around the heating system.
If water is not moving through the system as it should, your boiler may shut down to protect itself.
Common causes include:
- Low system pressure
- A circulation problem
- A faulty pump
- Air trapped within the heating system
- A blockage in the pipework or boiler
How To Fix ER 10 / E10
- Check the boiler pressure.
- Repressurise the system if the pressure is below the recommended level.
- Check whether any radiators are cold at the top or heating unevenly.
- Reset the boiler once.
- Contact a Gas Safe engineer if the problem continues.
If the same circulation issue keeps returning, it is important to investigate the underlying cause rather than repeatedly resetting the boiler.
ER 12 / E12: Hot Water Or Diverter Valve Problem
The ER 12 or E12 fault codes may indicate a problem affecting the boiler’s hot water operation or a component involved in directing water between heating and hot water.
On a combi boiler, the diverter valve helps manage whether the boiler is supplying central heating or hot water.
Possible causes include:
- A faulty diverter valve
- A sticking internal component
- A sensor or electrical fault
- A boiler control problem
How To Fix ER 12 / E12
- Reset the boiler once.
- Check whether you still have heating, hot water or neither.
- Make a note of any changes in the boiler’s operation.
- Arrange for a qualified engineer to diagnose the problem if the code remains.
Internal boiler components should only be inspected or repaired by a qualified professional.
ER 16 / E16: Fan, Electrical Or Internal Component Fault
The ER 16 or E16 codes can indicate a fault with an internal boiler component, depending on the model.
This type of fault can involve the fan, electrical connections or another component monitored by the boiler’s control system.
Potential causes include:
- A faulty fan
- Damaged wiring
- Loose electrical connections
- A failed internal component
- A control board fault
How To Fix ER 16 / E16
- Reset the boiler once.
- If the code returns, do not continue resetting it.
- Switch the boiler off if it is not operating correctly.
- Arrange for a Gas Safe registered engineer to inspect the boiler.
Electrical and internal component faults generally require professional diagnosis.
ER 25 / E25: Boiler Overheating Or Poor Water Circulation
The ER 25 or E25 error codes generally indicate that the boiler has detected unusually high temperatures, often because heat is not being moved away from the boiler effectively.
Common causes include:
- A faulty circulation pump
- A blockage in the heating system
- Air trapped in the system
- A partially closed valve
- Sludge or debris restricting water flow
- A fault with the temperature sensor
How To Fix ER 25 / E25
- Allow the boiler to cool down completely.
- Check the boiler pressure.
- Check that radiator valves are open where appropriate.
- Look for signs of poor circulation, such as radiators that remain cold.
- Reset the boiler once.
- Contact a Gas Safe engineer if the fault returns.
Persistent circulation problems may require professional cleaning, repair or replacement of affected components.
ER 28 / E28: Hot Water Flow Or Temperature Control Problem
The ER 28 or E28 codes can indicate a problem affecting the boiler’s ability to manage hot water flow or temperature correctly.
You may notice that your hot water becomes inconsistent, takes longer to heat up or is not available at all.
Possible causes include:
- A faulty hot water sensor
- A problem with water flow detection
- A diverter valve issue
- A blocked component
- An electrical or control fault
How To Fix ER 28 / E28
- Reset the boiler once.
- Check whether the fault occurs when using hot water only or during both heating and hot water operation.
- Make a note of any changes in water temperature.
- Contact a qualified engineer if the fault continues.
This information can help the engineer narrow down the cause more quickly.
ER 32 / E32: Temperature Sensor Or Electrical Connection Fault
The ER 32 or E32 error codes generally indicates that the boiler has detected a problem with a temperature sensor or the electrical connection linked to it.
Possible causes include:
- A failed sensor
- Loose wiring
- Damaged electrical connections
- A control board problem
How To Fix ER 32 / E32
- Reset the boiler once.
- Check whether the code clears.
- Do not attempt to access the boiler’s internal electrical components.
- Arrange for an engineer to inspect the boiler if the fault returns.
A professional diagnosis is important because several different faults can produce similar symptoms.
ER 36 / E36: Gas Supply, Ignition Or Flame Detection Problem
The ER 36 or E36 fault codes may be associated with a problem involving the gas supply, ignition process or flame detection.
The boiler may shut down if it cannot confirm that the burner is operating safely.
Potential causes include:
- A gas supply interruption
- An ignition fault
- A faulty flame sensor
- A gas valve problem
- An electrical connection fault
How To Fix ER 36 / E36
- Check whether other gas appliances are working.
- Check that the gas supply to the property has not been interrupted.
- Reset the boiler once.
- If the fault returns, stop attempting further resets.
- Arrange for a Gas Safe registered engineer to investigate the problem.
Never attempt to repair gas-related boiler components yourself.
ER 40 / E40: Central Heating Sensor Fault
The ER 40 or E40 error codes generally indicate that the boiler is receiving incorrect or no information from a central heating temperature sensor.
Common causes include:
- A faulty sensor
- Wiring damage
- Loose electrical connections
- A boiler control fault
How To Fix ER 40 / E40
- Reset the boiler once.
- Check whether the heating returns to normal operation.
- If the code remains, arrange for a qualified engineer to inspect the boiler.
The engineer may need to test the sensor and its electrical connection before identifying the exact cause.
ER 41 / E41: Boiler Temperature Sensor Fault
The ER 41 or E41 codes can indicate that a temperature sensor is not providing the information the boiler needs to operate safely.
Possible causes include:
- A faulty sensor
- Damaged wiring
- A loose connection
- A problem with the boiler’s control system
How To Fix ER 41 / E41
- Reset the boiler once.
- Check your Biasi boiler manual for model-specific guidance.
- If the code returns, arrange for a Gas Safe engineer to diagnose the fault.
Sensor faults may prevent the boiler from accurately controlling heating or hot water temperatures.
ER 42 / E42: Sensor Or Boiler Control Fault
The ER 42 or E42 error codes generally point to a problem involving a sensor, communication between components or the boiler’s control system.
Potential causes include:
- A faulty sensor
- Wiring or connection problems
- An internal electrical fault
- A problem with the boiler’s control board
How To Fix ER 42 / E42
- Reset the boiler once.
- Check whether the error code returns immediately.
- Record the exact code and your boiler model.
- Contact a qualified engineer if the problem continues.
Because this type of fault can have several possible causes, professional testing is usually the safest way to identify the problem.
Can Regular Boiler Servicing Help Prevent Biasi Boiler Fault Codes?
Yes, an annual boiler service can help prevent Biasi boiler fault codes caused by wear, developing component problems and issues that may be identified before they result in a complete breakdown.
During a professional boiler service, an engineer can inspect the boiler’s condition and check that it is operating safely and efficiently. While a service cannot prevent every future breakdown, identifying potential problems early may reduce the risk of being caught out by an unexpected fault.
For landlords, regular servicing is also an important part of keeping a rental property’s heating system properly maintained. Homeowners can benefit from the reassurance of knowing that their boiler is being checked regularly rather than waiting until heating or hot water stops working.
Knowing When a Biasi Boiler Fault Needs Professional Attention
Some Biasi boiler error codes may clear after a single reset or follow a simple issue such as low system pressure. However, with a wide range of faults covering ignition, overheating, flue operation, circulation, sensors and internal controls, it is important to recognise when the problem needs professional diagnosis.
You should arrange for a Gas Safe registered engineer to inspect your Biasi boiler if:
- ER 01, E01 or ER 36 keeps returning, as repeated ignition or flame-related faults can involve the gas supply, ignition system, flame sensor or gas valve.
- ER 02, E02, ER 25 or E25 appears again after the boiler has cooled, as recurring overheating may point to poor circulation, a faulty pump, a blockage or another internal problem.
- ER 03, E03 or ER 16, E16 is displayed, particularly where the fault may involve the fan, flue, air pressure system or internal electrical components.
- Low-pressure faults such as ER 04 or E04 keep returning after repressurising, as this may indicate a leak or another issue affecting the heating system.
- Sensor or control faults continue to appear, including codes such as ER 05, E05, ER 06, E06, ER 32, E32, ER 40, E40, ER 41, E41 or ER 42, E42.
- The boiler repeatedly shuts down, produces inconsistent heating or hot water, or displays the same code shortly after being reset.
With Biasi boiler faults, repeatedly clearing the error code does not address the reason it appeared in the first place. If the same problem continues, a qualified engineer can test the relevant components, identify the underlying fault and carry out the appropriate repair safely.
Stay Protected When Biasi Boiler Faults Become More Than a Simple Fix
While problems such as low system pressure may sometimes have a straightforward solution, recurring ignition faults, overheating, circulation problems and sensor issues can require professional diagnosis and repair.
Rather than being left to deal with an unexpected boiler breakdown and the potential costs that come with it, it can be worth putting protection in place before a more serious fault occurs. A PlusHeat boiler cover plan gives homeowners and landlords the opportunity to choose a level of cover that suits their property and helps provide reassurance when professional boiler repairs are needed.
FAQs
Why Is My Biasi Boiler Displaying A Fault Code But Still Working?
A Biasi boiler displaying a fault code while still working may be experiencing an intermittent issue or a fault that has not yet caused a complete shutdown. Make a note of the code and monitor the boiler, but arrange for an engineer to investigate if the code continues to appear.
Can A Power Cut Cause A Biasi Boiler Error Code?
A power cut can cause a Biasi boiler error code if the boiler experiences a disruption to its electrical supply or does not restart normally afterwards. Once power has been restored, check the boiler display and follow the manufacturer’s reset instructions if necessary.
How Do I Find The Exact Biasi Boiler Model?
You can usually find the exact Biasi boiler model on the boiler casing, control panel, installation paperwork or product documentation. Knowing the exact model is useful because fault code meanings can vary between different Biasi boilers.
Should I Turn My Biasi Boiler Off When An Error Code Appears?
You should turn your Biasi boiler off when an error code appears if the boiler is behaving unusually, the fault involves overheating, gas, the flue system or repeated shutdowns. For simple faults, follow the guidance in your boiler manual, but do not repeatedly reset a boiler that continues to display the same code.
Can A Biasi Boiler Error Code Clear Itself?
A Biasi boiler error code can sometimes clear itself if it was caused by a temporary interruption or an intermittent fault. However, a code that keeps returning should not be ignored, as this may indicate an underlying problem that requires professional diagnosis.
