Condensing Boilers, whether oil or gas burning, are about the most energy efficient Central Heating System boilers in buildings. The efficiencies typically may run as high as 98 % according to claims by the manufacturers. The same items on test beds of units of certifications according to for example SEDBUK of UK, on the other hand would show this to be around 95 % at best. In real life this can be typically about 82 % - 89% and would be about 90% at optimum operation. Bear in mind that all these efficiencies are worked out when High Heating Value (HHV) fuels are used and test conditions are near ideal.

In comparison In Conventional Boilers the efficiencies ranging from 70 % to 80% in operation. At that efficiency the near 50% capital cost increase of a new condensing boiler and controls is hard to justify. But is this inference correct?

To really understand the real economics encountered one must have a look at the working of a condensing boiler.

Working of a Condensing Boiler

A hot water boiler is a vital component of a central heating system of a building. A traditional boiler

makes use of the hot temperatures of flue gases generated as a result of burning of fuel oil or gas in the burner and combustion chamber, to heat up the circulating hot water in the central system .This is made possible by the use of a heat exchanger through a process akin to that of a car radiator. The combustion of hydrocarbon fuels also produces water as steam among other by products which is exhausted to the environment after passing through the heat exchanger to transfer the thermal energy to the heating system water.

In a conventional boiler it is a single pass and then out through the chimney or any other vent.

In the condensing boiler as the name implies, a condensing process is additionally incorporated. What condenses is the water in gaseous form (steam) generated within the combustion chamber. What you gain is the latent heat (of vaporization) released at the condensation of steam to liquid water. A note worthy fact is that, the water thus condensed is highly acidic and corrosive.

Efficiency of Oil burning condensing boilers

Manufacturers estimate their products can be fuel efficient up to about 98%. In practice the average efficiency is not more than 90%. This increase of about 12% in efficiency over the traditional boiler will conserve a considerable quantity of fuel oil over a year thus also making it easy on your purse. Naturally the lesser oil burnt means lesser harmful emissions, better carbon foot print and cleaner air.

Installation or retrofitting condensing boilers therefore entitles your t building for monetary grants, improved energy rating etc. from almost all state or any other sustainable energy agencies.

Overcoming the low efficiency

Makers of condensing boilers are constantly finding ways to improve energy efficiencies, durability

and reliability of their products. Viessmann one such leading manufacturers of condensing boilers in the western world, has developed techniques to overcome some major draw backs and also improve the efficiency at almost all temperatures.

Their heat exchanger of oil burning boiler is designed for 3 passes making it extract more thermal energy of combustion. The use of microprocessor controls to sense outdoor temperature variations and adjust the combustion process/ boiler water accordingly to optimize oil usage further improves efficiency Viessmann says. Their Vitotronic Control which is generally optional even allows for safe low temperature operation.