What next in the boiler room?

Industry comment

Published: 13 June

Type: Industry comment

Year: 2013

How can you achieve further energy savings even when your BMS, boiler and other heating controls have been optimised?  Tony Willis explains how

Many energy managers will already have implemented a number of measures to help reduce the energy consumption of their boiler plant. Obvious examples include ensuring the boilers are maintained regularly and perhaps installing AMR to help keep track of energy consumption. Other sensible measures would include checking that the BMS is optimised and, if it wasn’t already in place, introducing boiler sequencing and weather compensation strategies

Logical Step

However, further savings can be achieved by optimising each individual boiler to eliminate the boiler dry-cycling, which can potentially deliver additional savings of 10-25% (depending on site and application) with payback typically less than 2 years. These levels of savings can be achieved over and above those being delivered by existing control strategies. So when it comes to fine-tuning energy performance boiler load optimisation is the next logical step.

Boiler dry cycling occurs within each individual boiler, whereas most controls strategies are focused on the overall performance of the collective boiler plant. For example, in a commercial boiler room with two or more boilers a BMS will generally control heating and hot water systems by monitoring the blended water temperatures from all of the boilers and responding accordingly. It generally won’t be monitoring the boilers individually or fine tuning each boiler load.

Significant cost benefits if boiler dry cycling is prevented

This is where wasted energy occurs and goes unnoticed. Once the heating system is satisfied the boiler or boilers will naturally begin to cool down, once the temperature has dropped below the setting on the boiler’s thermostat (or as set by the BMS) the boiler will fire to recover this heat loss. This is boiler dry cycling – the boilers are only firing to recover their own heat loss; there is no actual heating demand from the building. If boiler dry cycling is prevented, significant cost savings and carbon emissions reductions can be achieved.

These issues have been recognised for many years but early attempts to tackle boiler dry cycling (some of which have re-emerged) relied on creating a delay between firing cycles or artificially lowering the boiler’s set point. These strategies have the potential to conflict with existing controls and compromise comfort conditions in the building – without delivering appreciable savings.

Real time control

Sabien’s patented M2G boiler load optimisation control uses adaptive software. It analyses each boiler’s flow and return temperatures every 10 seconds, and measures the decay of the flow and return temperature every second to provide a true load profile of each individual boiler in real time.

Just as importantly, it recalculates the values every time the boiler reaches its required set point temperature, so it adapts to BMS/optimiser variable set-points and does nothing to conflict with other existing controls such as weather compensation, demand control or sequencing. The boilers’ designed set points are not altered. Importantly M2G does not require any calibration or maintenance.

The result is that the M2G will enable you to deliver additional savings and carbon emissions which are currently going unnoticed in your boiler room.

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