How Is Exhaust Pipe Length Chosen for a Vertical All-in-One Diesel Air Heater?

Routing the exhaust for a vertical all-in-one diesel air heater looks simple, but pipe length and routing directly affect how the burner behaves. A small combustion fan pushes exhaust through a thin tube, and any extra length or kink works against it. Choosing the right run keeps combustion clean and reliable.

Keep It Short and Direct

Manufacturers specify a maximum exhaust length, often around one or two metres with a limited number of bends. Beyond that, back pressure builds and the fan struggles to expel gases. The flame runs less efficiently, exhaust becomes visible, and the controller may derate power.

Slope and Drainage

Condensation forms as exhaust cools, so the pipe should slope gently away from the heater so moisture drains outside rather than pooling. A low point inside the unit can freeze in winter and block the outlet. Avoiding uphill runs that trap condensate protects the burner through cold nights.

Separate From the Intake

The exhaust outlet must sit where its fumes cannot be drawn back into the combustion air intake, and away from windows or ventilation inlets. Keeping both ducts short, sealed, and positioned apart lets the burner breathe and expel exhaust cleanly, run after run.

Choosing the Right Pipe Material

The exhaust pipe must withstand repeated hot cycles without corroding, and a short, correctly specified tube lasts for years. Longer runs, or pipes routed where they cannot expand, stress the joints and invite leaks. Following the manufacturer's length limit and using the supplied flexible section absorbs vibration and movement.

Insulating an exhaust that passes near interior surfaces protects nearby panels from heat, while leaving the outlet end unobstructed. A pipe that meets length, slope, and separation rules gives the fan little resistance and keeps combustion clean.

A clean, correctly sloped exhaust also means the unit starts smoothly after long storage, because no condensation has frozen and blocked the outlet. This reliability is worth a little extra care during the initial install.

References

GB/T 7714: GUO R, LI L, SUN Z, et al. An integrated thermal management strategy for cabin and battery heating in range-extended electric vehicles under low-temperature conditions [J]. Applied Thermal Engineering, 2023, 228: 120502.

APA 7th: Guo, R., Li, L., Sun, Z., & Xue, X. (2023). An integrated thermal management strategy for cabin and battery heating in range-extended electric vehicles under low-temperature conditions. Applied Thermal Engineering, 228, 120502.

MLA 9th: Guo, R., et al. "An Integrated Thermal Management Strategy for Cabin and Battery Heating in Range-Extended Electric Vehicles under Low-Temperature Conditions." Applied Thermal Engineering, vol. 228, 120502.