Remeha Gas 620-510 Fault codes & diagnostics

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

Natural Gas 510 kW Discontinued

Replaced by: Gas 620 Ace

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.
1 Emergency 7 High
Just want the most common Remeha Gas 620-510 faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes

All 8 documented codes

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6.4.1 Flame control

Your boiler has stopped working because it cannot detect a flame, causing the system to shut down for safety.

High DIY-safe £120-350

What to check first

  1. Check if other gas appliances, like a cooker, are working to ensure gas supply is active
  2. Check that your gas meter has credit if you have a pre-payment meter
  3. Press the 'Reset' button on the control panel to see if the boiler restarts

Parts commonly replaced

  • Ionisation probe
  • Ignition electrode
  • Gas valve
Full explanation for 6.4.1 Flame control
6.4.2 Thermostats

Your boiler has switched itself off because its internal safety sensors have detected that it is getting too hot.

High Engineer only £180-450

Parts commonly replaced

  • Safety Thermostat
  • Safety Temperature Sensor
  • Heat Exchanger
Full explanation for 6.4.2 Thermostats
6.4.3 Water level control

Your boiler has shut down because it has detected that the water levels inside the system are too low to operate safely.

High Engineer only £180-450

Parts commonly replaced

  • Water level sensor
  • Low water pressure switch
  • Main PCB
Full explanation for 6.4.3 Water level control
6.4.7 Down draft thermostat

Your boiler has sensed that exhaust fumes are blowing back into the unit instead of escaping through the chimney, which has caused it to shut down for safety reasons.

Emergency Engineer only £180-450

Parts commonly replaced

  • Down draft thermostat
  • Flue sensor
  • Flue terminal/guard
Full explanation for 6.4.7 Down draft thermostat
Flame failure: lock out

Your boiler has stopped working because it cannot detect a steady flame and has shut itself down as a safety precaution.

High DIY-safe £120-450

What to check first

  1. Check if other gas appliances in your home, such as a gas hob, are working correctly to ensure gas is reaching the property.
  2. Ensure your gas meter has credit if you are on a prepayment meter.
  3. Press the reset button once to see if the boiler restarts, but do not attempt to reset it more than twice if it fails.

Parts commonly replaced

  • Gas pressure switch
  • Ignition electrode
  • Ionisation probe
  • Gas valve
Full explanation for Flame failure: lock out
Green zone; end of green zone

Your boiler is struggling to keep its main burner flame lit, which means it cannot heat the water reliably and will likely shut down.

High Engineer only £150-450

Parts commonly replaced

  • Ionisation probe
  • Ignition electrode
  • Gas valve
  • Burner gasket
Full explanation for Green zone; end of green zone
red zone

Your boiler is struggling to keep its internal pilot flame lit, which means the system cannot safely start up to provide heating.

High Engineer only £180-450

Parts commonly replaced

  • Ionisation probe
  • Ignition electrode
  • Gas valve
  • Pilot burner assembly
Full explanation for red zone
Water level control: lock out

Your boiler has switched itself off because it cannot properly detect the water level, which is a safety measure to prevent the system from running dry.

High DIY-safe £120-250

What to check first

  1. Locate the instrument panel on the front of the boiler.
  2. Press the 'Reset' button firmly once to see if the error clears.
  3. If the boiler restarts and runs normally, monitor it; if it locks out again immediately, you must call an engineer.

Parts commonly replaced

  • Water level electrode
  • Wiring harness
  • Ignition/Ionisation lead
Full explanation for Water level control: lock out