Ferroli Optima 201 Fault codes & diagnostics

33 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.

Combi Natural Gas 24 kW 2006-2010 Discontinued

Replaced by: Optima HE

Download the Ferroli Optima 201 manual The official installation & service manual (PDF) — the exact document these fault codes were verified against. PDF

This boiler uses LED flash patterns

Count the flashes in one repeating group before the pause. That number is your fault code. Do not reset until you have noted it. How to read fault codes →

Severity at a glance

Each cell = one fault code. Hover to identify.
26 High 4 Medium 3 Low
Just want the most common Ferroli Optima 201 faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes

All 33 documented codes

Tap any card for details

LED / flash-pattern codes
Display Flashing

Your boiler is struggling to start because the water pressure inside your heating system has dropped too low.

High DIY-safe £80-120

What to check first

  1. Locate the filling loop, which is usually a small silver braided hose or a plastic key underneath the boiler.
  2. Open the valves on the filling loop slowly to let water into the system.
  3. Watch the pressure gauge on the front of the boiler and close the valves once the needle reaches 1.5 bar.

Parts commonly replaced

  • Pressure gauge
  • Filling loop
  • Pressure relief valve

Related codes

Full explanation for Display Flashing
Red LED on/Flashing

Your boiler has safety-locked itself to prevent damage or because it failed to light three times in a row.

High DIY-safe £100-280

What to check first

  1. Check if your gas supply is active (e.g., check other gas appliances)
  2. Locate the reset knob/button on the control panel
  3. Turn the knob to 'Reset' for 2 seconds and release to see if the boiler restarts

Parts commonly replaced

  • Ignition Electrode
  • Gas Valve
  • PCB (Main Circuit Board)

Related codes

Full explanation for Red LED on/Flashing
Digital codes
LED 1 green (0)

Your boiler is currently completely unresponsive because it is not receiving any electrical power.

High DIY-safe £80-150

What to check first

  1. Check that the boiler isolator switch (usually a white switch near the boiler) is set to the ON position.
  2. Check your home's main fuse box (consumer unit) to see if any circuit breakers have tripped.
  3. Locate the fused spur next to the boiler and check if the replaceable fuse inside has blown.

Parts commonly replaced

  • External fuse
  • Fused spur switch
  • Printed Circuit Board (PCB)
Full explanation for LED 1 green (0)
LED 1: 0

Your boiler is not receiving any power, meaning it cannot turn on or provide any heating and hot water.

High DIY-safe £70-180

What to check first

  1. Check if other appliances in your home are working to ensure there isn't a general power cut.
  2. Ensure the boiler's power switch or fused spur on the wall is turned on.
  3. Check your property's main fuse box or consumer unit to see if a circuit breaker has tripped.

Parts commonly replaced

  • External fuse
  • Internal PCB fuse
  • Main PCB
Full explanation for LED 1: 0
LED 2 (D.H.W.)

Your boiler is failing to detect when you turn on your hot water tap, so it isn't starting up to warm the water.

Medium Engineer only £120-220

Parts commonly replaced

  • DHW Flow meter
  • Turbine sensor
Full explanation for LED 2 (D.H.W.)
LED 2 (DHW)

Your boiler is failing to detect that you have turned on a hot water tap, meaning it won't fire up to heat the water for your shower or taps.

Medium Engineer only £120-220

Parts commonly replaced

  • DHW flow turbine
  • Flow sensor

Related codes

Full explanation for LED 2 (DHW)
LED 2 yellow (0) [DHW mode]

Your boiler does not realise that you have turned on your hot water tap, so it is failing to heat the water for your shower or kitchen faucet.

High Engineer only £120-220

Parts commonly replaced

  • DHW Flow switch
  • Microswitch

Related codes

Full explanation for LED 2 yellow (0) [DHW mode]
LED 2: 0

Your boiler is not detecting when you turn on a hot tap, meaning you will likely have heating but no hot water.

Medium Engineer only £120-£210

Parts commonly replaced

  • DHW Flowmeter
  • Flow switch
  • Connecting wiring harness

Related codes

Full explanation for LED 2: 0
LED 4 (C.H.)

Your boiler has stopped heating your radiators because it is either detecting an overheating issue or is struggling to communicate with its internal temperature sensors.

High Engineer only £120-250

Parts commonly replaced

  • Central heating temperature sensor
  • Limit thermostat
Full explanation for LED 4 (C.H.)
LED 4 (CH)

Your boiler has detected an issue with its internal temperature sensing, meaning it cannot accurately judge how much to heat your radiators.

High Engineer only £120-220

Parts commonly replaced

  • Central Heating NTC Sensor
  • Wiring harness

Related codes

Full explanation for LED 4 (CH)
Showing 11–20 of 33
LED 4 (D.H.W.)

Your boiler has stopped producing hot water because it has lost contact with or is misreading the temperature sensor that monitors your hot water supply.

High Engineer only £120-220

Parts commonly replaced

  • DHW temperature sensor (NTC)
  • Wiring harness / connection cable
Full explanation for LED 4 (D.H.W.)
LED 4 (DHW)

Your boiler has lost the ability to measure the temperature of your hot water, so it has safely shut down to prevent overheating.

High Engineer only £120-180

Parts commonly replaced

  • DHW NTC thermistor sensor
  • Wiring harness

Related codes

Full explanation for LED 4 (DHW)
LED 4 green (0) [CH mode]

Your boiler has stopped producing heat because it is struggling to accurately read its own internal temperature or has overheated.

High Engineer only £120-220

Parts commonly replaced

  • Central heating NTC temperature sensor
  • Limit thermostat
  • Wiring harness
Full explanation for LED 4 green (0) [CH mode]
LED 4 green (0) [DHW mode]

Your boiler has stopped producing hot water because it believes the internal temperature sensor is either disconnected or reading an dangerously high temperature.

High Engineer only £120-200

Parts commonly replaced

  • DHW NTC Sensor
  • Wiring harness
Full explanation for LED 4 green (0) [DHW mode]
LED 4: 0

Your boiler has detected an issue with the sensor that monitors hot water temperature, which often means the water is getting too hot or the sensor has stopped working.

High Engineer only £90-160

Parts commonly replaced

  • DHW Temperature Sensor (NTC)
  • Wiring Harness
  • Main PCB

Related codes

Full explanation for LED 4: 0
LED 4: 0 (Central Heating)

Your boiler has stopped working because it thinks it is overheating or it cannot correctly read the temperature sensor for your radiators.

High Engineer only £90-180

Parts commonly replaced

  • Central heating temperature sensor (NTC thermistor)
  • Overheat limit thermostat
  • Wiring harness

Related codes

Full explanation for LED 4: 0 (Central Heating)
LED 5 (CH)

Your boiler is currently in a temporary self-imposed waiting period as part of its normal safety cycle and should restart automatically on its own shortly.

Low DIY-safe

What to check first

  1. Wait for 3 to 5 minutes for the countdown to finish
  2. Check that the room thermostat or programmer is calling for heat
  3. Ensure the boiler pressure is between 1 and 1.5 bar

Parts commonly replaced

  • Control board
  • System sensor

Related codes

Full explanation for LED 5 (CH)
LED 5 (DHW)

Your boiler's electronic control brain is experiencing a persistent internal error that prevents it from providing hot water or heating correctly.

High Engineer only £250-450

Parts commonly replaced

  • Printed Circuit Board (PCB)

Related codes

Full explanation for LED 5 (DHW)
LED 5 red (1) [DHW mode]

Your boiler has detected an internal computer error and is currently unable to start, meaning you will likely have no hot water or heating.

High Engineer only £250-400

Parts commonly replaced

  • Printed Circuit Board (PCB)

Related codes

Full explanation for LED 5 red (1) [DHW mode]
Showing 21–30 of 33
LED 5: 1

Your boiler's main internal computer has developed a critical electronic failure and can no longer process the startup sequence.

High Engineer only £280-450

Parts commonly replaced

  • Main Printed Circuit Board (PCB)

Related codes

Full explanation for LED 5: 1
LED 5: 1 (Central Heating)

Your boiler is temporarily pausing between heating cycles and should restart automatically within a few minutes.

Low DIY-safe

What to check first

  1. Wait 3 to 5 minutes for the countdown timer to finish
  2. Check that your room thermostat is turned up
  3. Ensure there is power to the unit and no other fault lights are flashing

Related codes

Full explanation for LED 5: 1 (Central Heating)
LED 6 (C.H.)

Your boiler has stopped working because it cannot detect enough water pressure or is struggling to read the temperature correctly, meaning it has safely shut itself down to prevent damage.

High Engineer only £120-250

Parts commonly replaced

  • Central Heating Temperature Sensor
  • Pressure Sensor
  • Limit Thermostat

Related codes

Full explanation for LED 6 (C.H.)
LED 6 (CH)

Your boiler has stopped working because it has detected an issue with its water pressure or internal temperature sensors.

High Engineer only £120-250

Parts commonly replaced

  • Central Heating NTC Sensor
  • Limit Thermostat
  • Pressure Transducer

Related codes

Full explanation for LED 6 (CH)
LED 6 (D.H.W.)

Your boiler has stopped working because it has detected a technical fault related to the water pressure or internal temperature sensors.

High Engineer only £120-250

Parts commonly replaced

  • DHW Sensor
  • Pressure Switch
  • Limit Thermostat

Related codes

Full explanation for LED 6 (D.H.W.)
LED 6 (DHW)

Your boiler has stopped working because it has detected an issue with its water pressure or internal sensors, preventing it from safely heating your home or water.

High DIY-safe £120-250

What to check first

  1. Check the boiler pressure gauge on the front panel; if it is below 1.0 bar, use the filling loop to top it up to between 1.0 and 1.5 bar
  2. Turn the boiler off at the mains for 60 seconds to reset the electronic fault
  3. Turn the boiler back on and observe if the error clears

Parts commonly replaced

  • DHW NTC Sensor
  • Pressure Transducer
  • Limit Thermostat

Related codes

Full explanation for LED 6 (DHW)
LED 6 yellow (0) [CH mode]

Your boiler has detected a faulty temperature reading caused by a sensor issue, which is preventing your central heating from turning on.

High Engineer only £120-200

Parts commonly replaced

  • Central heating NTC temperature sensor
Full explanation for LED 6 yellow (0) [CH mode]
LED 6 yellow (0) [DHW mode]

Your boiler is struggling to detect the temperature of your hot water because of a faulty connection or sensor, which means it will likely stop providing hot water until fixed.

Medium Engineer only £120-180

Parts commonly replaced

  • DHW NTC thermistor sensor
Full explanation for LED 6 yellow (0) [DHW mode]
LED 6: 0

Your boiler has detected an issue that could be caused by low water pressure or a faulty internal sensor, leading to a safety shutdown.

High DIY-safe £90-180

What to check first

  1. Check the pressure gauge on the front of the boiler; it should be between 1 and 1.5 bar.
  2. If the pressure is too low, use the filling loop to top up the system until the needle reaches the 1.5 bar mark.
  3. Restart the boiler to see if the fault clears; if the pressure is correct and the code remains, you will need an engineer.

Parts commonly replaced

  • D.H.W. Temperature Sensor (NTC)
  • C.H. Limit Thermostat
  • Water Pressure Switch

Related codes

Full explanation for LED 6: 0
LED 6: 0 (Central Heating)

Your boiler has detected low water pressure or a faulty internal sensor, causing the heating system to shut down for safety.

High DIY-safe £90-180

What to check first

  1. Check the pressure gauge on the front of the boiler; it should be between 1 and 1.5 bar.
  2. If the pressure is below 1 bar, use the filling loop to top up the system with water until it reaches the correct level.
  3. Restart the boiler to see if the fault clears.

Parts commonly replaced

  • Central Heating Temperature Sensor (NTC)
  • Water Pressure Switch
  • Limit Thermostat

Related codes

Full explanation for LED 6: 0 (Central Heating)
Showing 31–33 of 33
LED 7 green (0)

Your boiler has lost its connection to an internal sensor or controller, meaning it cannot detect the necessary conditions to fire up safely.

High Engineer only £120-220

Parts commonly replaced

  • Wiring harness
  • Main control PCB
Full explanation for LED 7 green (0)
LED 7: 0

Your boiler has detected an issue with the air flow or the internal fan, which means it cannot safely exhaust fumes and has shut down as a precaution.

High Engineer only £120-£350

Parts commonly replaced

  • Air Pressure Switch
  • Fan Assembly
  • Venturi Tube

Related codes

Full explanation for LED 7: 0
LED 8 yellow (0)

Your boiler has detected that it has become too hot and has safely shut itself down to prevent damage.

High Engineer only £120-250

Parts commonly replaced

  • Limit thermostat
  • Overheat sensor
  • Pump
  • PCB

Related codes

Full explanation for LED 8 yellow (0)
Status & diagnostic codes

9 operating states & engineer diagnostics

Not faults — these are normal operating states. Tap to expand.

Green LED on Status Your boiler is receiving power and is ready to work, but it hasn't been told to turn on the heating or hot water yet. LED 2 (C.H.) Status Your boiler mistakenly thinks you are running a hot tap because a sensor is stuck, which is preventing your central heating from turning on. LED 2 (CH) Status Your boiler is currently stuck in hot water mode because it wrongly thinks someone has turned on a tap. LED 2 yellow (1) [CH mode] Status Your boiler has correctly sensed that a hot water tap is running, and this light simply signifies that it is currently preparing to heat your water. LED 2: 1 Status Your boiler thinks a hot water tap is turned on even when all taps are closed, which may prevent your central heating from working. LED 3 (CH) Status Your boiler is currently waiting for a signal from your thermostat or timer to tell it that the house needs heating. LED 3 yellow (0) [CH mode] Status Your boiler is currently on standby because your thermostat or timer is not sending a signal to request heating. LED 3: 0 Status Your boiler is not receiving a signal from your thermostat or timer to turn on the heating. Orange LED on Status Your boiler is currently operating normally and the burner is ignited to provide heating or hot water.