Features include fully modulating burners giving accurate temperature control and high efficiency, minimal or no ductwork requirement, pressurisation of space to ensure a clean atmosphere, ventilation/cooling during summer months and flexible installation options.

To achieve the best solution for any large open space environment, careful consideration has to be given to a variety of factors, for two spaces of identical size and shape can present very different characteristics and requirements. 

Compare, for instance, an industrial warehouse where the majority of the activity involves semi-automatic fork-lifts carrying out ‘picking’ operations, with an exhibition space. Factors such as occupancy and lighting levels, as well as the size and usage of the entranceways could not be more different. 

It is vital for the specifier to not only calculate the heat load for the building accurately, but also to model the circulation in what is likely to be a very tall space. Furthermore, the requirements for ventilation, and the replacement of that air must also be taken into consideration. 

Many modern factories and warehouses feature the use of composite steel cladding panels whose insulated core cuts heat loss through the envelope to a good degree, but warmth will still be lost through ventilation. Where extraction is part of the production process – if dust is generated or fume cupboards have to be employed – this effect will be greatly pronounced. 

A supply of heated replacement air is therefore required to maintain comfort levels; and if it is not provided the extract system will perform inefficiently and a negative pressure can be created. This could lead to cold air being drawn in through leakage around the envelope. 

For new installations, the supply of heated make up air can often provide adequate ventilation, without the need to install additional extract units. However, where additional extract is deemed necessary, this can be integrated into the same unit to facilitate both input and exhaust flows; with the option of mechanical heat recovery from the exhaust side. 

The latest gas firing air heaters can meet these combined demands economically, featuring efficiencies of 100% (based on NCV) thanks to fully modulating burners and effective intelligent controls.

The Fully CE approved, Stokvis Econo-Air range of gas fired air heaters, for example, encompasses both direct fired (SDF) and indirect fired (SIDF) models which are able to achieve these multiple objectives. A turn-down ratio of 20:1 guarantees flexible response, while output rises from 15-900kW for the indirect units, and 30-1200kW with the direct firing options. There is also a comprehensive selection of accessories available, enabling the installation to be customised to the different requirements of the building concerned. 

For heating large open areas it is ideal to have a wide range of air distribution heads available in order to facilitate ductless distribution. This is achieved by slightly pressurising the internal space, to ensure even distribution both vertically and horizontally. This avoids the need for extensive duct runs or de-stratification fans. 

Where the building geometry does, however, demand ductwork, then Econo-Air units can be supplied with backward or forward curved fans to overcome resistance within the runs of up to 2000 Pascals.