Ferroli Optima 201 Fault codes & diagnostics

10 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 manualThe official installation and service manual (PDF), the document these fault codes were read from. PDF

The fault code is already on your display

Note it down before pressing reset — resetting clears the code immediately. How to read fault codes →

Severity at a glance

Each cell = one fault code. Hover to identify.
8 High 1 Medium 1 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 10 documented codes

Tap any card for details

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 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 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 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]
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 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 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

2 operating states & engineer diagnostics

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

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 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.