The Myths Surrounding Condensing Boilers

Myth: They are only efficient when fully condensing

Response: Due to its larger heat exchanger, a condensing boiler does not have to condense in order to be more efficient. Typically a new gas condensing boiler will have a seasonal efficiency of between 84% and 92% compared with a new non-condensing boiler at 78% or an older boiler at 55-65%.

The SEDBUK (Seasonal Efficiency of Domestic Boilers in the UK) rating is the average annual efficiency achieved in typical domestic conditions and is quoted in a series of bands (from ‘A’ at 90% or over, to ‘G’ at below 70%).The SEDBUK is linked to current Building Regulations in England, Wales and Scotland, but not Northern Ireland and some boilers which are rated A-B are suggested as ‘Energy Efficiency Recommended’.

Myth: They are too expensive

Response: In the past, condensing boilers were more expensive, mainly due to the materials used in the construction of the heat exchanger. However, as with all new things, the cost of technology reduces over time, and some regular condensing boilers can now be obtained for no more than a regular non-condensing boiler.

In some cases, the difference can be offset by grants that are available from local authorities, energy companies or via Energy Efficiency Advice Centres (EEACs).

Myth: They need larger radiators

Response: No change necessary. In most systems, radiators are already oversized for all but the severest weather. A marginal benefit of approximately 3% may be obtained from oversizing radiators for a new system, as this will allow slightly cooler return water to the boiler and maximise time spent in condensing mode, but this is usually uneconomic and impractical.

Myth: They are less reliable

Response:. This was true with the early models of condensing boilers, but through improvements introduced as a result of this early experience, the components in modern condensing boilers are as reliable as those in the equivalent non-condensing models.

Myth: They are difficult to install

Response: The only difference in comparison with non-condensing boilers is the requirement for a condensate drain. A competent installer will have no problem in deciding on a suitable location for the drain and fitting a normal, plastic overflow pipe.

Myth: They are harder to maintain

Response: The only minor difference is the need to ensure that the condensate drain is clear when servicing.

Myth: They cannot be fitted to existing systems

Response: Condensing boilers are suitable for replacing most existing boilers. As with any replacement boiler, the effectiveness of the control system and type of hot water cylinder should be assessed when conducting a site survey. Consideration should also be given to cleaning and flushing the system before fitting a new boiler. Wall hung condensing boilers are readily available, with extended fluing options if required.

Myth: They have limited availability

Response: The number of manufacturers offering both regular and combination condensing boilers is increasing all the time, with major players offering dozens of different models.