Heating tech is just warming up in the efficiency sector
The first step in achieving an energy-efficient heating system is to minimise demand for heat. This can be achieved by improving the insulation value of the structure, which will inevitably reduce the required heating load, thus allowing a reduction in the size of the plant required to heat the space.
Further improvements can be made by introducing a well-designed and correctly installed heating and ventilation system into the building, which will ensure the correct temperature rises to match the design criteria. Guidance can be sought on this subject from numerous sources such as building regulations approved documents L1 and L2, which provide guidance upon the minimum requirements of the regulations.
However, consideration should always be paid to the burners and boilers used within a heating system, as these have the potential to significantly drive down energy usage.
The first step in ensuring optimum efficiency is the confirmation that the burner is correctly matched up to the boiler/heat exchanger. This will ensure that the burner can provide an optimum turn down ratio, which will keep burner cycling to a minimum and will also ensure that there are no excessive heat losses in the stack or undesired condensing if the burner is too small.
The airflow of a typical blown burner is usually regulated by the graduation of an air shutter or damper via servomotors and cams. The fact that the fan is running at a constant speed inevitably incurs higher load losses, which in turn dissipates some of the electrical power generated by the fan motor.
The incorporation of an inverter drive can vary the RPM of the fan in correlation with the specific burner load, thus delivering energy savings and reduced noise levels.
The table (right) indicates the energy savings on a Baltur 450kW TBG 45PV by fitting an inverter drive to the fan motor.
The level of combustion efficiency can be predicted by comparing the quantity of O2 in the stack gases to that of theoretical or stoichiometric combustion conditions (assuming complete combustion). The lower the amount of O2 (or excess air), the higher the combustion efficiency.
Under normal operating conditions it is typical that the combustion engineer will set up the burner with a degree of excess air to ensure that it will not become starved of combustion air and begin to cause incomplete combustion. Several factors can affect the combustion process over time such as:
• barometric conditions;
• calorific value ; and
• mechanical hysteresis.
As it is not cost effective to have constant monitoring from an engineer, it is now possible to incorporate a constant monitoring system into the burner control. O2 trim systems gather the amount of oxygen present in the stack via a digital or analogue feedback system and then position the burner air damper to the appropriate position to maintain a consistent quantity of O2 throughout the full operating range of the burner.
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