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High Flue Draught with Tall Stove - Issues and Recommendations.

Why a Tall Three-Sided Woodburner with High Flue Draught Can Be Challenging to Control and Keep the Glass Clean.

 
  • Excessive Flue Draught:
    • A tall stove with a high flue creates a much stronger updraft, known as high flue draught.
    • This increased draught pulls combustion gases and air through the stove very rapidly, sometimes faster than ideal for controlled burning.
  • Difficult Temperature and Burn Rate Control:
    • The high draught can make it challenging to regulate the fire’s intensity, as the fire burns through fuel more quickly and can overheat.
    • Air controls may become less effective, as the strong pull draws in more air than intended, even when vents are partially closed.
    • This can lead to shorter burn times, increased fuel consumption, and less efficient heat output.
  • Impact on Air Wash and Glass Cleaning:
    • The air wash system is designed to direct a thin layer of pre-heated air over the inside of the glass to keep it clear of smoke and soot.
    • With a very strong flue draught, the air wash air may be pulled through too quickly, reducing its effectiveness at forming a protective barrier on the glass.
    • Rapid airflow can also disturb the combustion process, causing incomplete burning of fuel and resulting in more smoke or particulates, which can deposit on the glass.
    • In some cases, the strong draught may even draw smoke past the air wash before it has a chance to clean the glass, leading to more frequent staining and the need for manual cleaning.
  • Three-Sided Design Challenges:
    • With more glass surfaces exposed, there is a greater area to keep clean and more potential for uneven air distribution.
    • The strong draught can make it difficult for the air wash to be equally effective across all panels, especially the side glass, which may be more prone to staining if airflow is not balanced.
Summary:
A tall, three-sided woodburner with high flue draught can be hard to control because the excessive updraft pulls air and combustion gases through too quickly, making it difficult to regulate the fire. This also reduces the effectiveness of the air wash system, leading to less protection for the glass and more frequent build-up of soot and stains.
 
 
 
Advice for Mitigating High Flue Draught Issues in Tall, Three-Sided Woodburners
 
1. Installation Recommendations
  • Fit a Flue Draught Stabiliser (Damper):
    • Install a draught stabiliser or damper in the flue to regulate excessive updraft. This device can be adjusted to maintain optimal draught, preventing the fire from burning too fast and helping the air wash perform effectively.
  • Consider Flue Height and Insulation:
    • If possible, avoid making the flue unnecessarily tall. Work within the manufacturer’s recommended flue height for your stove model.
    • Properly insulate the flue to ensure a consistent temperature, which supports steady draught without excessive pull.
  • Use the Correct Flue Diameter:
    • Always match the flue diameter to the stove manufacturer’s specifications. An oversized flue can worsen draught issues, while an undersized flue can restrict airflow and cause smoke spillage.
  • Install an Anti-Down Draught Cowl or Rain Cap:
    • Fitting a suitable cowl can help moderate draught and prevent wind-related fluctuations, supporting more stable stove operation.
2. Operational Advice
  • Use Air Controls Effectively:
    • Start fires with air controls fully open, but once the fire is established, gradually reduce the primary and secondary air controls to slow the burn and maintain control.
    • Avoid running the stove with air controls wide open for extended periods, as this will increase the draught and reduce efficiency.
  • Burn Seasoned, Dry Wood Only:
    • Use wood with a moisture content below 20%. Wet or unseasoned wood produces more smoke and soot, making glass cleaning much harder, especially with high draught.
  • Don’t Overload the Stove:
    • Add moderate amounts of fuel at a time. Overloading can lead to rapid, uncontrolled burns and more smoke, which can overwhelm the air wash system.
  • Regular Maintenance:
    • Clean the glass frequently, even if only with a damp cloth or specialist stove glass cleaner, to prevent build-up.
    • Have the flue swept regularly to maintain safe and efficient operation.
3. Additional Tips for Glass Cleanliness
  • Check and Adjust Air Wash System:
    • Ensure air wash vents are clear and functioning. If the glass is still staining quickly, consult your installer about possible adjustments to the air wash or baffle system.
  • Run the Stove Hot Occasionally:
    • Periodically running the stove at a higher temperature (within safe operational limits) can help burn off deposits on the glass and inside the firebox.
  • Position Logs Properly:
    • Place logs so they do not touch the glass, as direct contact can lead to faster staining and restrict airflow along the glass surface.
Summary:
To mitigate high flue draught and keep your three-sided woodburner under control, focus on proper installation (draught stabiliser, correct flue height/diameter, insulation), careful operation (air control use, dry wood, moderate fuelling), and regular maintenance. These steps will help maintain effective air wash performance, keep the glass cleaner for longer, and ensure safe, efficient stove use.