The next generation of condensing solutions promises to expand the use of high-efficiency boilers and increase energy savings, writes John Thomason, general manager at Atmos Heating Systems
The heating industry is now familiar with condensing boilers and their cost- and energy-saving benefits. But contractors may not be aware of a new generation of condensing solutions that can both solve tricky installation problems and further increase the boilers' efficiency.

One of the bugbears with condensing boilers, particularly for local authorities, is that they are incompatible with the ordinary SE ducts typically used on multi-storey buildings. But the Communal Flue System (CFS) allows condensing boilers to be fitted in blocks of flats or similar projects, which allows installers, public-sector specifiers and developers meet energy-efficiency standards.

The CFS is already proven in multi-storey developments in the Netherlands, where condensing boiler technology is well established. It is available in the UK from Atmos, and was launched at the Installer Live exhibition in Coventry last year. This approach can handle up to 20 boilers on one stack, delivering sufficient combustion air while providing for the efficient discharge of flue products, and eliminating issues with multiple pluming from the side of a building.

It is well suited to new-build projects and can also be used as a retrofit solution for developments already equipped with an SE duct system, thus enabling standard boilers to be replaced with high-efficiency condensing units.

A new brochure from Atmos illustrates the available configurations. These include the naturally vented, or the more compact fan-assisted system. The system works with condensing, non-condensing or a mixture.


The siting and installation of a condensing boiler's condensate drain can cause problems for contractors. But Atmos' Intergas range of condensing boilers comes with a drain-free option which, the company says, is the only product of its type on the market. Designed to take the hassle out of boiler siting and installation, the drain-free condensing boiler works by collecting condensate in a special chamber adjacent to the boiler.

When the condensate reaches a certain height, it automatically switches on a pump to remove water from the chamber, discharging it through a fine mist nozzle at the end of the flue terminal.

There have been other improvements to condensing technology, and increasing environmental benefits. Boiler SEDBUK ratings consider central heating (CH) efficiency, not domestic hot water (DHW). Yet, hot water efficiency, already measured in the Netherlands, is seen as the next step forward for UK boilers. Similarly, a boiler's electrical energy use is also rated in Europe, though not yet in the UK.

Atmos Heating Systems says it takes a wider view of environmental performance in designing gas boilers. The Atmos InterCombi (HE32) condensing boiler, for example, uses 19% less energy and 25% less water for DHW than other combi condensing gas boilers.

According to Atmos, the boiler's heat exchanger is the key. The integral single-tube DHW circuit enables condensing operation to work for both hot water and central heating. This means that the boiler operates in condensing mode for hot water, which results in a DHW rating of 89% efficiency compared with an average of 75% for most other condensing combis.

This design also improves electrical efficiency because it heats the DHW directly. This means the circulation pump is switched off in DHW operation - typically, combis require a 105W circulation pump for DHW.

Further electrical savings can be made through the HE32's controller which has a switched-mode power supply. This is more energy efficient than the linear power supply used in most gas boilers. In standby mode, the HE32 uses only 2.4W of power. The result can reduce this boiler's electricity consumption by an impressive 89% when compared with the average condensing combi.

Producing instantaneous hot water in this way means the HE32 also uses 25% less water. Generally, combis take 45 seconds before the water is hot at the tap. Research shows this can waste as much as 25,000 litres of water a year, a significant consideration with water meters. Further savings are made through the HE32's intelligent Eco mode self-learning timer, which ensures the boiler only heats up DHW during periods of actual use.

From a sustainability perspective, the use of condensing boilers in major contracts for local authorities, housing associations and property developers must widen. And the boilers that are installed need to offer the best possible energy savings and environmental benefits. Condensing boilers are a big step towards energy efficiency but manufacturers still need to strive for greater savings and further innovation.