How to Fix Worcester Greenstar 30CDi Fault Codes

The Worcester Bosch Greenstar 30CDi is a reliable, efficient boiler. Like any boiler, it can throw a fault code now and then. The code on the display tells you something is wrong, but not always what to do about it.

This guide covers the common Worcester Greenstar 30CDi fault codes, what causes them, and what you can safely check before you call an engineer.

About the Worcester Greenstar 30CDi

The Worcester Bosch Greenstar 30CDi is a wall-mounted, gas-fired boiler built for homes with higher heating and hot water demand. It is known for solid performance and good energy efficiency.

To keep it running well, it needs regular servicing once the initial guarantee runs out. A yearly service catches small problems before they turn into breakdowns.

Worcester Greenstar 30CDi Fault Codes and What They Mean

A fault code shows on the display when the boiler hits an operational problem. Here are the common ones and what they point to.

• EA – Flame Not Detected: The boiler cannot detect a flame when it should. Common causes are a disrupted gas supply, a blocked or frozen condensate pipe, or a flue problem. Check the gas is on and the condensate pipe is clear.
• C6 – Fan Speed Too Low: The fan that vents flue gases is running too slowly. Usually wear, an electrical fault, or an obstruction. The boiler will not run safely without the fan working properly.
• E9 – Safety Temperature Limiter Tripped: The safety limiter has cut in, usually because the heating has overheated. Trapped air, low water pressure, or a faulty thermostat can cause it.
• F0 – Internal Error: A general internal fault. The cause is not obvious from the code, so it needs an engineer to diagnose
• F7 – Flame Detected When Boiler Is Off: The boiler senses a flame when it should be off. Often a faulty gas valve or ignition fault. This is a safety issue — get it looked at straight away.
• FA – Flame Detected After Gas Shut-Off: A flame is still present after the gas is cut. Could be a faulty gas valve or residual gas. Needs a qualified engineer
• Fd – Reset Button Pressed Accidentally: Shows when the reset button is pressed by mistake. Fix any underlying issue first, then restart the boiler following the manufacturer’s steps.
• b1 – Code Plug Not Detected: The boiler cannot read the code plug, which it needs to run properly. Usually a loose connection, a damaged plug, or one that needs replacing.

If basic checks do not clear the fault, get a Gas Safe registered engineer to look at it. Showing a code that is not listed here? Our guide to the full range of Worcester Bosch fault codes covers the rest of the Greenstar lineup.

Serviceteam is a Worcester Bosch Silver Accredited Installer in London, working with homeowners across the city.

What Causes Worcester Greenstar 30CDi Fault Codes?

Causes vary by code. The common ones are:

• Gas supply issues — low or no gas can trigger EA.
• Condensate blockages — a frozen or blocked condensate pipe causes problems, mostly in winter.
• Flue problems — a blocked or damaged flue restricts airflow and can bring up EA or C6.
• Component failure — the fan, gas valve, or safety limiter can fail.
• System pressure — trapped air or low pressure can trigger certain codes.

How to Fix Worcester Greenstar 30CDi Fault Codes

Some issues are safe to check yourself. Others need an engineer. Here is what you can do first.

• Check the gas supply: Make sure the gas is on and working elsewhere in the home. If you are not sure, contact your gas supplier.
• Check the condensate pipe: Frozen condensate pipes are common in cold weather. Thaw gently with warm water.
• Bleed the radiators: Trapped air in the system can cause faults. See our guide on how to bleed a radiator.
• Reset the boiler: Switching it off and on can clear some codes, like Fd.
• Check the thermostat and controls: If the heating is not reaching temperature, make sure the controls are set right.

A word of caution: we do not recommend DIY repairs on a boiler. They are complex, and getting it wrong risks your safety and can cause more damage. If you are a qualified gas engineer, that is different — work safely and follow the right precautions.

For anything beyond these basic checks — gas supply faults, fan failures, blocked flues — book a boiler repair in London with a Gas Safe registered engineer. Running a faulty boiler is not safe, and it usually costs more to fix later.

Boiler Safety Basics

What to Do If You Smell Gas

A gas leak is dangerous. If you smell gas:

• Do not create flames or sparks — no smoking, matches, or lighters.
• Do not switch electrical appliances or switches on or off.
• Turn off the gas at the meter.
• Open windows and doors to let the gas out.
• Get everyone out and warn your neighbours. Keep people away.
• Call the National Gas Emergency Service on 0800 111 999 from a safe distance.

Using Your Boiler Safely

The Greenstar 30CDi is built to heat a sealed domestic hot water and heating system. Using it for anything else can damage it and void the warranty. Stick to what it is designed for.

Keep up with servicing and watch for the signs your boiler needs a service.

When to Call a Professional

Boilers mix gas and electrics, so DIY repairs carry real risks — gas leaks, electrical hazards, voided warranties. Always use a certified engineer for:

• Installation and setup
• Servicing and annual boiler maintenance
• Emergency repairs

For any of these, use a Gas Safe registered engineer or qualified electrician.

Why Choose Serviceteam for Boiler Repairs

Serviceteam handles boiler repairs across London. Our Gas Safe registered engineers diagnose boiler faults and attempt repairs promptly, so your home can get back to normal safely.

Why London homeowners use us:

• Experienced with Worcester Bosch boilers, including the Greenstar 30CDi
• Repairs from £104 + VAT when booked online
• Accurate diagnosis
• Engineer will assess, diagnose, and attempt to repair within the first hour
• Fixed-price quote, no hidden costs
• Gas Safe registered engineers

Worcester Greenstar 30CDi stuck on a fault code? Book a Gas Safe engineer with Serviceteam — online bookings from £104 + VAT, with an engineer who will assess, diagnose, and attempt to repair within the first hour.