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7 ways to ensure a condensing boiler achieves top results

Upgrading to condensing boilers can transform the comfort and energy performance of a school building, says Chris Meir, Sales Director at Remeha

Posted by Lucinda Reid | October 28, 2017 | Facilities management

As budgets shrink and environmental commitments increase, identifying and implementing cost-effective energy efficiency improvements wherever possible makes perfect financial and environmental sense. So where to start? As heating typically accounts for around half the total energy consumption in schools and colleges, it’s a frequent recommendation.

In the UK, commercial boiler plant still provides the heating for a large proportion of educational establishments. Yet many of these boilers are ageing or inefficient, needlessly wasting energy and creating unnecessarily high bills.

Failing boilers can also impact on learning ability. A report by the World Green Building Council Temperature found that performance can fall on average by 6% if a room is too hot and 4% if too cold. Ensuring reliable, efficient heating therefore plays an important part in generating the optimum learning environment in schools and colleges.

New heating equipment is, by design, more efficient.  25-year-old boilers will struggle to achieve 70% gross efficiency, even when well-maintained. In contrast, condensing boilers, the cleanest, most efficient boiler type, can achieve gross efficiencies of up to 97% and ultra-low NOx emissions at or below 40mg/kWh. The savings potential is clear.

So how do we ensure that condensing boilers deliver the anticipated results? It all comes down to good system design.

1. Good design

Condensing boilers are 10-12% more efficient than non-condensing boilers due to their ability to recover both sensible and latent heat from flue gases. But the system return temperature must be at or below dew point (normally around 54°C) to enable them to fully condense.

Older buildings will typically have been sized on 82°C flow and 71°C return temperatures. Lowering the flow and return temperatures to 70/50°C or even 60/40°C will allow the condensing boilers to achieve their maximum efficiencies without affecting comfort. This is possible as radiators in older educational buildings are often oversized due to changes to the fabric of the building or its use.

2. Appropriate selection

No two projects are the same, so selecting the right equipment for each individual job is essential. Ask manufacturers to pay a site visit as they will be able to advise on the most appropriate solution to meet project, site and budget requirements. This is particularly important on heating requirements below 400kW where like-for-like replacement may no longer be possible due to changes from the Energy-related Products Directive.

3. Accurate sizing

Take time to recalculate the building’s current load demand as this could have changed since the last boilers were installed. Oversized or undersized boilers will perform less effectively and efficiently, driving up bills and failing to create the most comfortable classroom environment.

4. Cascade arrangement

Condensing boilers operate more efficiently at part load, so look to install multiple boilers rather than one single unit. As condensing boilers modulate according to heat demand, installing multiple boilers will also increase the turndown ratio, enabling them to match the fluctuating demand more closely and reduce waste.

The reduced wear and tear increases the lifecycle of the boilers for whole life savings. Servicing and maintenance is also easier while the heating provision is more secure and reliable, all of which minimises any disruption or inconvenience.

5. Effective control

Good control is vital to achieve and maintain high efficiency heating. For schools and colleges, we recommend including time, temperature, weather compensation, zoning and sequencing controls, all of which must be fully integrated into the Building Management System to maximise energy savings. Routine checks will ensure that control settings remain correct.

6. Thorough commissioning

This is crucial stage of the project that must not be rushed. Good hydraulic, combustion and controls commissioning will help ensure that the heating system performs as designed. 

7. Maintaining high performance

Finally, implement a proactive maintenance and servicing programme as this will keep performance heating high.

In condensing boilers, schools and colleges have an affordable solution to high performance heating. The immediate and long-term fuel savings they deliver when replacing older boilers will help bolster the coffers. And with the cleaner, more reliable heating promoting a productive learning environment, students, staff and bursars are all winners. But to benefit fully from the huge energy savings potential, it pays to follow these seven steps and ensure good system design.

For more information about Remeha, visit 

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