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How to choose the right hot air generator

Combustion type, fuel, required output and installation: what matters when choosing a hot air generator for a hall, a construction site or a farm.

1. Direct or indirect combustion

Direct combustion (no flue): the combustion gases enter the room together with the warm air. Efficiency is practically total and heating is fast, but these units are only used in very well ventilated or open spaces: construction sites, buildings under construction, open warehouses.

Indirect combustion (with flue): the flame burns in a separate chamber and the combustion gases are discharged through a flue. Only clean warm air reaches the room. This is the right choice for enclosed spaces where people work or animals are kept: halls, workshops, greenhouses, farms, events.

2. Fuel

  • Diesel: independent of the gas network; suited to construction sites and remote locations.
  • Natural gas or LPG: low running costs where a connection or cylinders are available; used mainly with direct combustion.
  • Electric: no combustion and no exhaust gases; for small or enclosed spaces and for building drying.
  • Infrared: heats people and objects directly, not the air; efficient in open or semi-open spaces where warm air would be lost.

3. Required output — a quick estimate

A commonly used rule of thumb: P (kcal/h) = V × ΔT × K, where V is the volume of the space in m³, ΔT the difference between the desired and outdoor temperature, and K an insulation factor:

  • K ≈ 0.6–0.8 for well insulated buildings;
  • K ≈ 1–1.5 for average insulation;
  • K ≈ 2–3 for poorly insulated buildings;
  • K ≈ 3–4 for uninsulated spaces, marquees or temporary structures.

To get kW: kW = kcal/h ÷ 860. Example: a 20 × 10 × 5 m hall (1,000 m³) with average insulation (K = 1.5) and a 15 °C difference needs about 1,000 × 15 × 1.5 = 22,500 kcal/h, roughly 26 kW.

This is only an estimate. For an exact recommendation, send us the dimensions of the space, the type of building and the desired temperature.

4. Mobile or suspended

Mobile generators are easy to move between locations and suit construction sites and temporary work. Suspended units are mounted on the ceiling or wall, keep the floor clear and are preferred in halls, workshops and farms. High-capacity models can be connected to ducting to distribute warm air to several areas.

5. Power supply and safety

Check whether the model needs a single-phase or three-phase supply. Always follow the manufacturer’s instructions on ventilation, safety distances and flue gas discharge, especially with direct combustion.