Main Eco Compact 30 Combi Fault codes & diagnostics

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

Combi Natural Gas 24-30 kW 2018 onwards
GC Number 47-467-15
Download the Main Eco Compact 30 Combi manualThe official installation and service manual (PDF), the document these fault codes were read from. PDF

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Severity at a glance

Each cell = one fault code. Hover to identify.
8 High 1 Low
Versions & GC numbers

Which version do you have?

The GC number on your boiler's data badge identifies the exact appliance and production years, as recorded in the UK Product Characteristics Database.

GC number Appliance (register name) Produced
47-467-15 ECO COMPACT 30 COMBI 2018–present

Appliance names and production years are taken from the UK Product Characteristics Database (the SAP/SEDBUK register). Where a GC number is also printed in this model's own manufacturer manual, both sources were checked to agree.

Fault codes

All 9 documented codes

Tap any card for details

110

Your boiler has detected that the water inside the system has become too hot and has automatically shut down to prevent damage.

High Engineer only £120-250

Parts commonly replaced

  • NTC temperature sensor
  • Pump
  • Heat exchanger

Related codes

Full explanation for 110
118

Your boiler has stopped working because the water pressure inside the heating system has dropped too low.

High DIY-safe £80-150

What to check first

  1. Locate the external filling loop, which is usually a small braided metal hose with one or two valves underneath the boiler.
  2. Open the valve(s) slowly to allow water into the system until the pressure gauge on the front panel reads between 1.0 and 1.5 bar.
  3. Close the valve(s) firmly and check the display to see if the error code has cleared.

Parts commonly replaced

  • Filling loop
  • Pressure relief valve
  • Pressure sensor

Related codes

Full explanation for 118
125

Your boiler has detected that the water inside the system isn't circulating or heating up correctly, preventing it from operating safely.

High Engineer only £150-350

Parts commonly replaced

  • Pump
  • Diverter valve
  • NTC thermistor sensor
  • Primary heat exchanger

Related codes

Full explanation for 125
128

Your boiler has stopped because the flame inside has gone out unexpectedly while it was trying to heat your home or water.

High Engineer only £120-250

Parts commonly replaced

  • Gas valve
  • Ignition electrode
  • Flame sensor
  • Printed Circuit Board

Related codes

Full explanation for 128
133

Your boiler is failing to light because it cannot detect a flame, likely due to a gas supply issue or a blockage.

High DIY-safe £120-250

What to check first

  1. Check if other gas appliances, like a gas hob, are working to confirm your gas supply is active.
  2. Ensure your gas emergency control valve (usually by the gas meter) is fully open.
  3. Check if your gas prepayment meter has run out of credit.
  4. Press the 'Reset' button on the front of your boiler to attempt a restart.

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Condensate trap
  • Printed Circuit Board (PCB)

Related codes

Full explanation for 133
134

Your boiler is failing to light because it cannot detect a flame, which means your heating and hot water have stopped working.

High Engineer only £120-250

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Printed Circuit Board (PCB)

Related codes

Full explanation for 134
135

Your boiler has stopped working because it cannot light the internal flame or maintain it, likely due to a gas supply issue.

High Engineer only £120-250

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • PCB

Related codes

Full explanation for 135
Bat

Your boiler's backup battery accessory has an error or has run out of power, which usually means the system cannot save its settings or time during a power cut.

Low DIY-safe £10-50

What to check first

  1. Locate the Safety Assist accessory module connected to your boiler
  2. Check if the batteries inside the accessory need replacing (usually standard AA or AAA)
  3. Ensure the battery compartment is clean and the batteries are inserted correctly
  4. Restart the boiler to see if the message clears

Parts commonly replaced

  • AA/AAA Alkaline Batteries
  • Safety Assist Module

Related codes

Full explanation for Bat
E4

Your boiler is having trouble moving water around the system properly before it fires up, often caused by trapped air or low pressure.

High DIY-safe £100-280

What to check first

  1. Check the pressure gauge and top it up to 1.5 bar if it is too low
  2. Ensure all radiator valves and isolation valves under the boiler are fully open
  3. Gently bleed your radiators to remove any trapped air from the system
  4. Reset the boiler by turning the selector switch to 'R' for five seconds

Parts commonly replaced

  • Circulating pump
  • Flow temperature sensor
  • Automatic air vent

Related codes

Full explanation for E4
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