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Exploring the success of retrofit boiler controls

29 July 2015

Why is it that retrofit boiler controls are now making a significant contribution to energy and carbon reduction strategies? There are several reasons…

Many organisations have already reduced energy wastage, especially electricity, and are now turning to gas and oil. Obvious measures include ensuring there are controls in place and the control strategies are aligned to current building usage and plant efficiency is maintained through regular maintenance.

Once these measures have been taken, retrofitted boiler optimisation controls are increasingly used to reduce energy consumption further and are often recommended in Energy Performance Contracts.

So why are retrofit boiler controls so popular?

Retrofit boiler controls require relatively low investment, deliver proven savings, are simple to deploy and deliver significant and quick financial returns.

Yet it is sometimes assumed that boiler controls will not deliver further efficiency gains if a BMS or other controls are already in place. This assumption is often incorrect because these controls do not typically address the issues of dry cycling caused by standing losses.

Dry cycling can be identified by observing the boiler firing for short, regular periods – and also shows in analysis of Half Hourly data.

The rapid uptake of boiler load controls therefore brings an additional level of control. Sabien’s M2G only addresses boiler dry cycling, it does not replicate or duplicate the BMS functions. This is why organisations such as BT, O2, Aviva and the MoD have all invested in this technology – as well as investing in modern BMS controls and boilers.

Over 9,500 Sabien M2G boiler controls have been installed worldwide, delivering cost-savings of 10-25% with typical paybacks under 2 years, and as they are self-learning there is no requirement for ongoing maintenance or commissioning.

How do boiler controls work?

Unlike many other attempts to control boiler dry cycling, M2G does not delay firing, lower the boiler’s operating temperature, conflict with existing control strategies or compromise comfort conditions. Instead, it provides real time analysis of each boiler’s heat loss on the flow and return and recalculates the values every time the boiler reaches its required set point temperature.

This means it adapts to BMS/optimiser variable set-points and, crucially, the boilers’ designed set points are never altered.


Measurement and verification is important in any energy-saving initiative. Sabien recommends that savings are verified in line with the International Performance Measurement and Verification Protocol (IPMVP). This provides full transparency and ensures savings analysis is based on actual kWh rather than boiler runtime savings

Why not use the BMS?

Typically a BMS is configured to control the heating system as a whole rather than monitoring and controlling each individual boiler – making it impossible to identify dry cycling at individual boiler level.

Other factors include:

• Re-programming a BMS can be expensive when hardware, programming, commissioning and ongoing maintenance costs are taken into account.
• A multi-site estate may have several BMS and boiler types, each requiring its own re-programming procedure.
• Retrofit controls such as M2G can be easily deployed estate-wide to over 95% of boilers.


As organisations search for further savings within their estates, boiler load optimisation should be one of the first technologies considered and deployed to deliver this. However, energy managers must ensure their BMS supplier and the boiler control supplier engage effectively so that a full understanding of the technology and the demarcation between the control strategies is understood by all.

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