As many organisations consider how to reduce carbon emissions and energy costs, the heating plant is likely to come under close scrutiny. Inefficient heating plant can be very wasteful of energy but, at the same time, it may not be old enough to warrant investment in new plant.

In such cases it's worth considering modernisation of the plant, whereby an upgrade programme increases efficiency without a huge investment. In particular, it's worth looking at the burners and the boiler controls to see if their operation can be enhanced. In both cases there have been advances in technology that can deliver significant improvements with a fast payback.

For example, modern burners provide tighter control of combustion air, which reduces wasted heat and improves heat exchange in the boiler. Alongside this, increased turndown capabilities reduce cycling, wear and thermal stresses – and help the boiler respond more efficiently to heat demands from the building.


Many new burners incorporate variable speed drives, reducing electrical consumption by up to 30% - with lower firing rates and reduced combustion air.

It's also worth noting that low NOx boilers are being introduced to the market, using flue gas recirculation or premix technologies to deliver NOx levels well below the most demanding legislative requirements.

Boiler Controls

As noted earlier, boiler controls are also worth a look, as efficient control is essential for optimum efficiency. For instance, upgrading from high/low operation to modulating control aligns the boiler output more closely to the flow temperature – giving better response to varying heat loads.

A Case In Point:

Hoval was recently called in to a client in Scotland to modernise two Hoval ST Plus 950kW boilers, originally installed in 2001. As the original mechanical burners had reached the end of their service life, new burners were installed. The result was a 37% decrease in NOx emissions and nearly 3% improvement in combustion efficiency.

Crucially, the new burners have also given a new lease of life to the 21-year-old boilers, providing the client with trouble-free heating for many years to come – without a major investment in new heating plant.