Introduction
Boiler Controls are specifically designed equipments that maximize the efficiency of new and / or existing boiler and burner plant. Boiler Controls equipment is considered to include the following:
Oxygen Trim Controls
Oxygen trim controls automatically monitor the oxygen or carbon monoxide concentration in boiler flue gases and vary the air/fuel supply to the burner to limit excess or low oxygen concentrations in the fuel/air mix.
Oxygen trim controls are a means of controlling air: fuel ratio on a real time basis. The system uses an in situ oxygen probe with an electronic analyzer/controller. Together they provide a control output to the air or fuel controller. The probe is mounted at a representative position in the flue gas path. Care must be taken to ensure that the probe is sited well away from the burner flame paths.
The probe is connected to the analyzer which calculates the oxygen concentration in the flue gases. The control output is passed to a signal limiter containing the desired set point and then to a ratio controller that operates a motorized valve on the fuel line and motorized damper on the air intake to maintain the desired ratio.
 Burner Systems
Burner systems are designed to provide boiler modulation and combustion control through the use of digital microprocessor based systems with the aim of optimizing energy use. New burners with controls or retrofit burner control systems can be fitted.
Burner systems continuously measure either the temperature or pressure in the heating system and modulate the burner to match the measured demand, adjusting the burner from firing at 100% down to 40 – 50% for oil burners and down to 25% for gas burners. The system will also measure the oxygen and carbon monoxide levels in the flue gasses and adjust the air: fuel ratio to maintain preset levels. The system achieves this control through servo actuators connected to all appropriate valves and dampers on the burner and also through variable speed drives (VSD) on the burner fan
Sequencers
sequencer controls optimize fuel usage by managing the firing sequence of different boilers to ensure that the most efficient boiler(s) are selected to match the prevailing load conditions.
Boiler sequencer control systems are microprocessor based systems which measure the heating system flow and return temperatures and then isolate or control multiple boilers to ensure that the most efficient boiler(s) are selected to match the prevailing load conditions. The control system stores and references the control parameters of each individual boiler and uses this data to optimise the firing sequence.
 Metering
Energy meters can track boiler performance and report boiler system energy consumption to the user.
Energy metering systems are microprocessor based systems which measure the appropriate boiler parameters (Flow, temperature, pressure, fuel consumption) and then calculate the associated energy usage. This information is displayed on a local panel and can be logged to a Building Management System (BMS) thus can track boiler performance and report boiler system efficiency to the user.
Typical Energy savings for each of the technologies are listed below:
Oxygen Trim
- 2 – 5% reduction in fuel costs
- Typical payback periods 1 – 4 years
- Reduced carbon emissions
 Burner Systems
- 25-40% reduction in fuel costs
- Typical payback periods 2 – 4 years
- Reduced carbon emissions Sequencers
- 12-15% reduction in fuel costs
- Typical payback periods 2 – 4 years
- Reduced carbon emissions
Metering
- 2 – 5% reduction in fuel costs, higher when used in conjunction with other technologies
- Typical payback periods 1 – 4 years
- Reduced carbon emissions
