Ferroli Boiler Error Codes Guide to Common Problems

If your Ferroli boiler displays an error code, you need clear answers fast—especially when you’re left without heating or hot water. This guide is for UK homeowners and landlords who want to decode what each error means, find practical steps to fix simple issues safely, and know when it’s time to call a Gas Safe registered engineer.

Below, you’ll find straightforward explanations of common Ferroli boiler error codes, what causes them, and what to do next for reliable heating and peace of mind.

Common Boiler Problems and Error Codes

Modern boilers, including those from Ferroli, are fitted with electronics designed to monitor how the appliance runs. When the system detects a fault—such as low water pressure or an issue with the gas supply—it will display an error code and often shut down for safety.

It’s important to note that error codes can vary slightly between different Ferroli models. Always check your boiler’s user manual for model-specific guidance. These codes act as a diagnostic tool, pointing to the likely cause of any issues. While some basic checks, like topping up low pressure, can be carried out by homeowners, any work involving gas components or the inside of the boiler must legally be performed by a Gas Safe registered engineer.

Attempting repairs on gas appliances without the proper certification is unsafe and against UK law. If you’re unsure or the fix involves more than the simplest external checks, call a Gas Safe engineer for assistance.

Typical Ferroli Fault Codes and Their Meanings

Ferroli boilers use a range of codes to signal different issues. Below is a breakdown of some of the most common error codes you might see on your combi, system, or regular boiler.

Ferroli A & F Error Codes 

These are some of the most frequent codes.

• A01 / F1: Indicates an ignition failure. This usually points to a problem with the ignition electrode, gas supply interruptions, or an electrical power issue.
• A02: Indicates a flame has been detected when the burner is off. This fault usually means the gas valve or control board needs to be checked by a Gas Safe engineer.
• A03: Indicates overheating, often resulting from poor water circulation or a problem with the boiler’s pump. The safety thermostat shuts the boiler down when it detects that water temperature is too high to prevent damage.
• F37: Indicates low system water pressure, usually below 1 bar. This is a common and straightforward issue that can often be fixed by repressurizing the boiler using the filling loop until the pressure gauge reads about 1.0–1.5 bar, ideally 1.3 bar.
• F5 (often shown as F05): This code points to an air pressure switch fault or a flue obstruction. It can also be triggered by a frozen condensate pipe in cold weather, which restricts safe removal of boiler waste gases.

Ferroli D Codes (e.g., D1, D2)

These codes typically relate to sensor or thermostat faults.

• D1: Domestic hot water sensor fault. The boiler cannot read the hot water temperature accurately, leading to either no hot water or water that is not at the set temperature.
• D2: Central heating sensor fault. The system can’t correctly monitor the water temperature for the heating circuit.

Other Common Ferroli Error Codes

• F04 / F07: These codes signal electronic board faults or issues with the air pressure switch. Either the control board isn’t operating as expected, or the air pressure switch isn’t detecting correct airflow, which can be linked to issues with the fan or blockages in the flue.
• A09: Indicates a fault with the gas valve or a wiring disconnection. This should always be checked and repaired by a Gas Safe registered engineer.
• F43: Heat exchanger protection has been triggered, usually due to poor water circulation caused by sludge buildup or pump failure.
• A06: No flame detected after the ignition sequence. This could relate to gas supply problems, ignition electrode issues, or faults with the burner.

Always refer to your Ferroli boiler manual for codes specific to your model. If you are ever unsure or the fault indicates a component or gas-related issue, contact a Gas Safe registered engineer for assistance.

This is not an exhaustive list, and you should always consult your boiler’s user manual for a full list of codes specific to your model.

DIY Troubleshooting for Common Boiler Issues

Some minor boiler issues can be addressed without an engineer. Use these straightforward checks to diagnose or solve common faults.

How to Fix Low Boiler Pressure (F37 Error)

Low pressure is a frequent fault, often linked to small leaks, system bleeding, or pressure loss over time.

1. Check the Pressure Gauge: The gauge is usually on the front panel. Normal pressure when cold should be between 1.0 and 1.5 bar—ideally 1.3 bar. Below 1 bar, the system needs topping up.
2. Locate the Filling Loop: Find the silver braided hose with one or two small taps underneath the boiler.
3. Repressurise the System: Open the filling loop taps slowly. Water will enter the system and the gauge will rise.
4. Set the Correct Pressure: Close the taps as the needle approaches 1.3 bar (do not exceed 1.5 bar).
5. Reset the Boiler: Most Ferroli models need the reset button held for 5–10 seconds to clear certain error codes.

No Heating or Hot Water

If your boiler is running but you have no heating or hot water, check the following:

• Thermostat Settings: Ensure your room thermostat is set for heat and, if wireless, has working batteries.
• Boiler Pressure: Low pressure will prevent the boiler from firing. Check the gauge as above.
• Gas Supply: Ensure other gas appliances (like your hob) work. If not, check that the gas shutoff valve beside the appliance or meter is open.

Frozen Condensate Pipe

Condensate pipes can freeze in cold weather, causing the boiler to shut down and potentially display a flue or fan error (e.g., F5/F05). The pipe is typically a white or grey plastic tube running to an outdoor drain.

• Safely thaw the pipe: Pour warm (not boiling) water over the pipe outside, or wrap it with a hot water bottle or warm cloth to gently melt any blockage.
• Reset the boiler: After thawing, hold the reset button for 5–10 seconds to clear the error code.

If issues persist after these steps, do not attempt further repairs—professional help will be needed.

While some fixes are straightforward, many boiler problems require professional attention. It is illegal and extremely dangerous for anyone who is not on the Gas Safe Register to work on a gas boiler.

You must call a Gas Safe registered engineer if:

• You suspect a gas leak (you can smell gas).
• The boiler fault code points to an internal component failure (e.g., pump, fan, gas valve, or PCB).
• You have repressurised the boiler, but the pressure drops again quickly, which suggests a leak in the system.
• The boiler casing needs to be removed for any reason.
• You are not confident in carrying out any of the DIY checks.

An engineer has the training, tools, and legal certification to work on gas appliances safely. They can accurately diagnose the fault and replace parts correctly. Always ask to see their Gas Safe ID card before they begin work.

Preventative Maintenance Tips

Regular maintenance helps prevent boiler problems and keeps your heating running efficiently.

• Annual Servicing: Book a Gas Safe engineer to service your Ferroli boiler every year. Annual servicing checks key safety and efficiency points, and can spot sensor or electronic issues before they become serious.
• Bleed Radiators: Release trapped air from your radiators a couple of times a year. This helps maintain even heat and keeps system pressure stable.
• Monitor Pressure: Check the boiler pressure gauge now and then. If it drops below 1.0 bar, use the filling loop to bring it up to the recommended 1.3 to 1.5 bar.
• Run the Heating: Turn your heating on for 10–15 minutes every few weeks in warmer months. This keeps parts like the pump moving so they don’t seize up.
• Flush the System for Overheating Errors: If you get repeated overheating faults, a system flush may be needed to clear sludge from pipes and the heat exchanger, not just component replacement.

Consistent care extends your boiler’s life and reduces the risk of breakdowns, especially during colder months.

What do Ferroli boiler error codes mean?

Ferroli error codes are diagnostic indicators. Each code, such as F37 or A01, points to a specific fault within the boiler’s system, like low water pressure or an ignition failure. This helps identify the problem for troubleshooting.

How do I fix low boiler pressure?

To fix low pressure, you need to use the boiler’s filling loop to add more water to the system. Open the taps on the loop until the pressure gauge reads around 1.5 bar, then close them. You may need to reset the boiler afterwards.

When should I call a Gas Safe engineer?

You must call a Gas Safe engineer for any work that involves removing the boiler’s casing or interacting with its gas-carrying components. This includes repairs to the gas valve, fan, pump, or internal electronics. It is also required if you suspect a gas leak.

How much do boiler repairs cost?

The cost of a boiler repair can vary significantly depending on the fault. A simple fix might cost £80-£150, while replacing a major component like the main circuit board (PCB) could cost £300-£500 or more.

Are boiler problems covered by home insurance?

Standard home insurance policies do not typically cover boiler breakdowns. However, many providers offer separate home emergency cover or specific boiler cover as an add-on, which would cover the cost of repairs and parts. Check your policy details to see what is included.