Baxi · Combi & System 2 platform
H.01.08Flow temperature increasing too quickly in heating mode; ten-minute pause
This code applies to Baxi 200 Combi 2, Baxi 400 Combi 2, Baxi 600 Combi 2, Baxi 800 Combi 2, Baxi Assure 500 Combi 2, Baxi 600 System 2, Baxi 800 System 2, Baxi Assure 500 System 2. Fault codes narrow down the likely problem, but they do not replace a model-specific diagnosis.
What you can safely check
- Check the system pressure and make sure accessible radiator valves are open.
- Allow an overheated boiler to cool and reset once only if the user manual permits it.
- If the fault returns, stop resetting and arrange an engineer.
How an engineer may fix it
Diagnose water circulation, air locks, pump operation, valves, bypass, blockages, heat exchanger and temperature sensors; restore correct flow and test the safety controls.
Manufacturer source: Baxi Professional — Boiler Error Codes. Checked 15 August 2026. The appliance manual and an engineer’s on-site diagnosis take precedence. Never remove the boiler case yourself.