Biomass Flue System for Spira and Vecta Boilers

Biomass Flue System for Spira and Vecta Boilers

This 125mm (5") vertical conventional stainless steel, twin wall insulated flue system is specifically designed for use with all Grant pellet boilers. 

It has been fabricated to cope with continuous operating temperatures of up to 200○C although the typical flue gas temperature produced by Grant biomass boilers is less than 80○C. The system is designed so that the stainless steel outer case is load bearing and stainless steel inner liner is free to expand independently to accommodate temperature change. 

Features & benefits

Available with a range of extension pieces and bends, the system can easily be assembled to suit a wide variety of installations. 


Biomass flue system components are joined together by placing the female collar of one section over the corresponding male collar of the preceding section then locking by rotating the upper section clockwise. It is vital that all flue components are installed with the male collar pointing upwards. An arrow on the label indicates the flue gas direction.  

The inner of each section is enlarged at the male end so that the female end of the other section or fitting enters into it and overlaps. This allows any condensation to run back to the boiler without escaping from joints. 

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Flue Runs

The flue should remain as straight as possible through its vertical run to assist flow. Should it be necessary to angle the flue run, an offset no greater than 45○ to the vertical, with a run between the bends not exceeding 20% of the overall height of the chimney should be maintained. A vertical rise of 600mm should be allowed immediately above the appliance before any offsets.  Flue systems should be installed to the requirements of the Building Regulations Document J (England, Wales, Northern Ireland & Republic of Ireland) and building standards (part F) in Scotland. Flue must be a minimum of 60mm away from any combustible material

  • Twist-lock bayonet jointing system including seals, secured by locking bands
  • Advanced corrosion resistant design and construction uses laser welded stainless steel inner liner and case
  • The 25mm high efficiency Superwool blanket maintains flue gas temperature, maximising efficiency, improving flue draught on start up and minimising condensation.
  • Low external case temperature
  • Inner liner held by the male locking collar but free to expand and contract with temperature by up to 18mm through the female collar
  • The inner liner has an inward bead at the female end which acts as a capillary break preventing moisture being drawn through the joint.
  • CE certified denotes it is fully compliant with regulations in force from 1st July 2013
  • Internal flue system components available in white or black powder paint finish
  • External components available in black powder paint finish only


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