flat burner

Hamworthy Purewell Boiler:Transformation from low to high efficiency with Burnertech technology


Several years ago, Burnertech were asked to look at an improvement, from the existing atmospheric Purewell design (Figure 1). The original design was sent to the design lab at Burnertech.


We started a bespoke burner design for the boiler provided to us. The key parameters that guided our design were:

  • I. Remove the existing atmospheric gas burner and replace it with a premix burner
  • ii. Keep the physical footprint the same
  • iii. Improve the performance of the Boiler on efficiency
  • iv. Improve the NOx and CO performance
  • v. keep the price competitive.
The main aim of the new design was to fire the burner from the top of the boiler rather than below. As the long-term aim was to improve the efficiency of the unit to a condensing boiler. We removed the existing atmospheric burners from below the boiler and placed the new designed flat premixed burner above the boiler castings also designing a collector box at the base of the boiler which incorporated the flue outlet. Hamworthy then re-designed the castings when the unit was returned to them and incorporated a secondary heat exchanger in our collector box.


With this new design, we have successfully transformed the existing Purewell low efficiency atmospheric boiler to a low NOx, fully premixed, modulating, condensing and high efficiency boiler that the Variheat is today.

As of now (November 2017), we have provided for our customer over 9,000 units of the Variheat premix burners.

Hamworthy Variheat Boiler