Gas heaters produce much lower exhaust temperatures than wood stoves, which makes chimney sizing harder: with condensing technology the flue gases are sometimes below 80 °C. If the chimney is oversized or poorly insulated, the gases cool too quickly. Condensation forms, the chimney gets damp, and the draught breaks down.
DruckZugPro checks whether your existing chimney works with the planned gas heater. The calculation per DIN EN 13384-1 accounts for the low temperatures and flags condensation issues before they occur.
Highlights
- Calculation tuned for the low exhaust temperatures of gas appliances.
- Dew point check included: shows whether condensation will form inside the flue.
- Supports both standard-efficiency and condensing boilers.
How it works
- Select your gas appliance from the database or enter nameplate data (output, exhaust temperature, mass flow).
- Describe your chimney: height, cross-section, material, insulation.
- The result shows whether draught and temperature stay within limits, and whether condensation is expected.
FAQ
Why is the calculation different for gas heaters vs. wood stoves?
Wood stoves produce exhaust temperatures of 200 to 400 °C. Condensing gas boilers sit at 40 to 80 °C. At such low temperatures the dew point becomes the limiting factor: if the flue gas temperature drops below the dew point inside the chimney, water condenses out. The chimney must be moisture-resistant, or the gases must stay warm enough.
Can I use an old masonry chimney for my gas heater?
Often yes, but only with a moisture-resistant liner (e.g. stainless steel or plastic flue pipe). DruckZugPro shows whether the cross-section fits and whether condensation is expected. In doubtful cases the chimney sweep must confirm suitability.
What does “moisture-resistant” mean?
Gas exhaust contains a lot of water vapour. When it condenses inside the chimney, the material must withstand the moisture. Stainless steel and certain ceramics qualify. Traditional masonry without a liner does not.