Building In Quality

To offer boilers with a warranty of up to 10 years, we need to be really confident in their reliability. And we build that reliability in, right from the start during the design stage. Long before we make the decision to launch a boiler into the marketplace, we carry out numerous tests on the complete boilers and also their individual components.

Extensive life testing can simulate aggressive, extreme conditions, in a laboratory environment.  We test boilers flat out 24/7 for at least 12 months (the equivalent of five years under normal conditions), setting up worst case scenario conditions, such as air in the system or dry fire.  Our laboratory has a wind machine, so we can test how boilers work in extreme weather conditions.  We also have a ‘quiet’ chamber, so we can accurately measure how much noise they make when working.

We also test single components to destruction in environmental chambers at different atmospheric pressures, humidity and extremes of temperature, from -20 to +40 degrees.

And we carry out extensive field trials, so the boilers are exposed to different climates and conditions in a variety of different homes and situations.

Once we are satisfied with the quality and reliability of the boiler, we can start production.  We test every single boiler as it makes its way along the production line.  Tests include: 


  • Gas soundness test
  • Combustion soundness test
  • Electrical safety test
  • Hydraulic pressure test


During in-process checks, each operator is responsible for the work they carry out, and visual checks are made all along the process. Also, every operator is given sufficient time to ensure quality checks are completed for their part of the process and only when the last person finishes does the line move on – this means no one is rushing. All these processes are tracked to make sure nobody is working too quickly or too slowly.


Once the boiler is completely built, we carry out full functional tests using water, electricity and gas, which takes about six minutes.  The boiler’s barcode is scanned, and its serial number, test results, date and time of manufacture, which test rig was used, who carried out the tests, product information is all recorded for complete traceability.


  • A demand is made on the boiler simulating its use in the home. The sequence of operation is checked.
  • The gas rate is checked to make sure it is functioning correctly.
  • Lost gas is simulated to make sure the boiler shuts down safely, and then fires up again when it is reset.
  • The heat load/gas rate is checked to make sure it is within tolerance according to instructions.
  • The load is reduced (eg from 30kW to 15kW) and the gas valve is checked to make sure it reacts and modulates down to the correct load, and that the gas rate is correct for the new level.
  • The Carbon dioxide level is checked using a sensor in the flue pipe. The gas valve is adjusted to the correct carbon dioxide level – so the boiler leaves the factory fine-tuned for optimum performance, efficiency and safety.
  • As the boiler is now full of water, the hydraulics are all checked again.


Every boiler has to pass every test before it leaves the production line. Before packing the boiler goes through the kit scanning process.  It can’t be wrapped and go into stock unless it has passed all the tests and has all its correct accessories and literature with it.


Our first time good rate is 99.4%, but we still carry out single event analysis on every boiler that fails to pass the full function tests, using a root cause and effect tool to find out what went wrong.  This is very similar to the approach taken by the British Olympic cycling team.  Their manager Dave Brailsford’s principle was that if you make tiny improvements to each thing that impacts the rider, those marginal gains will add up to a much bigger overall improvement.  It certainly worked for that team and it has also proved to be very successful for team Baxi!