Baxi Suprima 30 Fault codes & diagnostics

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

Regular Natural Gas 8.8 kW 1998-2010 Discontinued
GC Number 41-607-75

Replaced by: Potterton Promax HE

Download the Baxi Suprima 30 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.
14 High 2 Medium 3 Low
Just want the most common Baxi Suprima 30 faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes

All 19 documented codes

Tap any card for details

LED / flash-pattern codes
1 red flash

Your boiler has detected that it is overheating or that water is not moving through the system correctly, causing it to shut down for safety.

High DIY-safe £120-280

What to check first

  1. Check that all radiator valves are open and not turned to off
  2. Ensure your system water pressure is topped up to roughly 1.5 bar
  3. Press the reset button once to see if the fault clears

Parts commonly replaced

  • Temperature Sensor (Thermistor)
  • Circulation Pump
  • PCB (Control Board)

Related codes

Full explanation for 1 red flash
2 red flashes

Your boiler has become too hot and has automatically shut down for safety purposes.

High DIY-safe £120-350

What to check first

  1. Wait for the boiler to cool down for at least 20 minutes
  2. Check that all radiator valves are open and not blocked by furniture
  3. Press the 'Reset' button on the front control panel
  4. Check if the pressure gauge is at least 1 bar (if a system boiler)

Parts commonly replaced

  • Overheat Thermostat
  • Circulation Pump
  • PCB (Control Board)
  • Thermistor

Related codes

Full explanation for 2 red flashes
3 green flashes

Your boiler has temporarily lost its flame and is attempting to restart its sequence automatically.

Medium Engineer only £120-350

Parts commonly replaced

  • Flame sense electrode
  • Ignition lead
  • PCB (Control Board)

Related codes

Full explanation for 3 green flashes
3 red flashes

Your boiler is failing to light its internal flame after several attempts, meaning your heating and hot water will not work.

High DIY-safe £120-350

What to check first

  1. Check that your gas emergency control valve is in the 'on' position
  2. Check if other gas appliances like a hob are working to confirm gas supply
  3. Press the 'Reset' button firmly for two seconds and wait for the boiler to restart

Parts commonly replaced

  • PCB (Control Board)
  • Ignition Electrode
  • Gas Valve

Related codes

Full explanation for 3 red flashes
4 green flashes

Your boiler is experiencing a brief communication hiccup between its internal electronic parts and should correct itself automatically.

Low DIY-safe £0-280

What to check first

  1. Monitor the boiler for a few minutes as it should self-reset
  2. If the error persists, turn the control knob to the 'Reset' position for 5 seconds
  3. Ensure any external controls or thermostats are calling for heat

Parts commonly replaced

  • Main PCB
  • Control Knob/Interface Board
Full explanation for 4 green flashes
4 red flashes

Your boiler's internal cooling and exhaust fan is not spinning correctly, which is preventing the system from starting up for safety reasons.

High Engineer only £180-350

Parts commonly replaced

  • Fan Assembly
  • Air Pressure Switch
  • PCB (Printed Circuit Board)

Related codes

Full explanation for 4 red flashes
5 green flashes

Your boiler has experienced a brief electronic glitch in its internal computer, but it should clear itself automatically once it recalibrates.

Low DIY-safe £250-450

What to check first

  1. Wait for the boiler to automatically reset itself
  2. If the flashing continues for more than 10 minutes, turn the power switch off and back on again
  3. Observe if the fault returns regularly, as this may indicate a failing board

Parts commonly replaced

  • PCB (Printed Circuit Board)
  • Control Knob/Interface
Full explanation for 5 green flashes
5 red flashes

Your boiler’s internal computer chip has encountered a technical memory error and can no longer communicate with the main control board.

High Engineer only £180-350

Parts commonly replaced

  • Parameter Storage Unit (PSU)
  • PCB (Printed Circuit Board)

Related codes

Full explanation for 5 red flashes
6 green flashes

Your boiler has experienced a temporary hiccup and is currently trying to reset itself to resume normal operation.

Low DIY-safe £0-120

What to check first

  1. Wait up to 15 minutes for the boiler to automatically reset
  2. If it does not reset, press and release the reset button once
  3. Ensure there is power to the boiler and the gas supply is active

Parts commonly replaced

  • None (usually self-clearing)
  • PCB (if fault persists)
Full explanation for 6 green flashes
6 red flashes

Your boiler has encountered an internal logic error and cannot tell exactly what is wrong, which has caused it to stop working for safety.

High Engineer only £180-350

Parts commonly replaced

  • PCB (Printed Circuit Board)
  • Ignition Lead
  • Electrode Probes
Full explanation for 6 red flashes
Digital codes
110

Your boiler has become too hot and has shut down as a safety precaution to prevent damage.

High DIY-safe £90-250

What to check first

  1. Turn off the boiler and allow it to cool down completely.
  2. Check and bleed all radiators using a radiator key to release trapped air.
  3. Ensure all radiator valves (TRVs) are fully open.
  4. Press the reset button on the boiler control panel once cooled.

Parts commonly replaced

  • Overheat Thermostat
  • Circulating Pump
  • Flow/Return Thermistors
Full explanation for 110
125

Your boiler has sensed that water is not moving around the system correctly, causing it to overheat and shut down for safety.

High DIY-safe £150-350

What to check first

  1. Check that your central heating valves and radiator valves are open
  2. Ensure your system water pressure is between 1.0 and 1.5 bar
  3. Try resetting the boiler to see if the fault clears
  4. Gently bleed your radiators to remove any trapped air pockets

Parts commonly replaced

  • Central heating pump
  • Overheat thermostat
  • Automatic air vent

Related codes

Full explanation for 125
127

Your boiler has failed to heat the water in your cylinder to a high enough temperature to kill off potentially harmful bacteria.

Medium DIY-safe £90-220

What to check first

  1. Check that your hot water cylinder thermostat is set to at least 60°C
  2. Ensure your boiler control knob is not turned to the 'minimum' or 'off' position
  3. Check your programmer to ensure the hot water heating window is long enough (at least 1 hour) for the tank to reach full temperature

Parts commonly replaced

  • Cylinder Tech thermostat
  • NTC Immersion Sensor
  • PCB (Control Board)

Related codes

Full explanation for 127
133

Your boiler has tried to light several times but has been unable to successfully create a flame to start the heating process.

High DIY-safe £120-£350

What to check first

  1. Check that your gas supply is turned on at the meter
  2. If you have a prepaid gas meter, check that you have sufficient credit
  3. Press and hold the reset button for five seconds

Parts commonly replaced

  • Ignition electrodes
  • Gas valve
  • Ignition lead
  • Printed Circuit Board (PCB)

Related codes

Full explanation for 133
160

Your boiler has detected an issue with the part that clears waste gases, preventing the system from starting for your safety.

High Engineer only £250-450

Parts commonly replaced

  • Fan assembly
  • Printed Circuit Board (PCB)
  • Air pressure switch

Related codes

Full explanation for 160
E12

Your boiler has detected that water isn't moving through the system correctly, so it has shut down to prevent overheating.

High Engineer only £120-280

Parts commonly replaced

  • Circulating pump
  • Differential pressure switch
  • Main PCB

Related codes

Full explanation for E12
E78

Your boiler is unable to accurately measure the water pressure inside the system, which is preventing it from heating your home safely.

High Engineer only £140-220

Parts commonly replaced

  • Water pressure sensor (transducer)
  • Wiring harness
  • Main PCB

Related codes

Full explanation for E78
OFF OFF OFF

Your boiler has no power, meaning the display is blank and the heating is not working at all.

High DIY-safe £0-120

What to check first

  1. Check that the boiler power switch or fused spur next to the boiler is turned on.
  2. Check your home's main consumer unit (fuse box) to see if a circuit breaker has tripped.
  3. Replace the 3-amp fuse in the boiler's power spur switch.

Parts commonly replaced

  • 3-amp fuse
  • Printed Circuit Board (PCB)
  • Wiring loom
Full explanation for OFF OFF OFF
ON OFF ON

Your boiler has tried to light several times but failed, meaning it has now locked itself out for safety.

High DIY-safe £100-350

What to check first

  1. Check if your gas supply is active (for example, by testing a gas hob)
  2. Locate the reset button on the front control panel
  3. Press and hold the reset button for at least 5 seconds and release

Parts commonly replaced

  • PCB (Control Board)
  • Ignition Electrode
  • Gas Valve
Full explanation for ON OFF ON
Status & diagnostic codes

1 operating states & engineer diagnostics

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

1 green flash Status Your boiler has reached its set temperature and is temporarily pausing until the water cools down enough to start heating again.