Boiler controls


Keeping up with the evolution of boiler controls

The principle of new technologies improving on or complementing old ones is well established, and is clearly illustrated in the evolution of boiler controls

New technologies solve problems, increase efficiency and often give us greater control over day-to-day processes. And, in the main, each technological advance improves on the last to deliver better performance. This is certainly the case with retrofitted boiler controls, which have advanced considerably during the past 40 years.


In the 1970s, for example, “time delay” devices were introduced to try to prevent boiler dry cycling, where the boiler fires to replace heat lost through standing losses rather than in response to a genuine requirement for heat in the building or process. Unfortunately, these prevent the boiler from firing on the basis of a fixed time delay, rather than by temperature. Consequently, firing might be delayed even when there was a genuine need for heat in the building, resulting in suppressed temperature. Controls using a time-delay approach are still on the market and suffer from the same limitations.


In the 1980s, the introduction of microprocessors enabled building management systems (BMS) and building optimisation, with a positive effect on the efficiency and control of heating in buildings. These technologies have continued to evolve and, when properly commissioned and maintained, remain as the vanguard of boiler control in many commercial applications.


Nevertheless, most BMS are not configured to detect or control the ongoing problem of boiler dry cycling directly, so the 1990s saw the introduction of “load compensation” or “burner management” controls. Many of these result in lowering the boiler’s design operating temperature by 2-5°C, using a single temperature sensor to monitor the boiler’s return temperature. Without monitoring both flow and return water temperatures these devices cannot differentiate between boiler dry cycling and firing to meet a genuine demand for heat. Consequently the boilers cannot respond to a genuine demand and comfort temperatures can be compromised. Some of these devices also use a timer to record how long the burner has or hasn’t been firing – presenting this as actual energy saving – which isn’t the case. They can also cause issues with weather compensation and other control strategies and are not compatible with emerging control strategies.


These issues led to a new approach to address dry cycling in the early 2000s – Intelligent Boiler Load Optimisation – in the form of Sabien’s patented M2G. M2G is unique in that it does not lower set points or the system’s average temperature. Instead, it uses real time measurement and analysis of both flow and return water temperatures to identify the boiler load specifically and whether the boiler is dry cycling or whether there is a genuine heating demand. Furthermore, it is compatible with all current and future BMS. Indeed, the majority of the 8,000 M2Gs in use across Europe, the US and Asia are installed alongside modern BMSs. Analysis demonstrates average energy savings of 12% with payback approximately 18 months.

The future

There can be no doubt that buildings and their services will be expected to become ever more efficient in the future, in line with tighter energy consumption and emissions targets. Using the latest boiler controls, that also incorporate an element of future-proofing, is clearly the logical way to achieve greater energy efficiency.

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