Parallel controls use separate motors to regulate fuel flow and airflow, enabling each motor to be tuned throughout the boiler ignition range. During installation, to points are usually drawn to create a curve of airflow corresponding to the fuel flow. The air-fuel ratio can be varied along the ignition range to prepare the optimal ratio in different ignition conditions. Also with the use of electronic dampers, this method of control is very reproducible.

Engine room boilers have capabilities that have made them the main and common part of buildings. Boilers have a long life, and boiler efficiencies can achieve efficiencies of % and above, provide effective methods for heating buildings, and require very little or zero pumping energy in steam systems. But fuel can be significant, and regular maintenance is required by the facility engineer, and if it is delayed, the cost of repairing the engine room can be high.

If a building has multiple boilers, you may be able to use the boilers in sequence to prevent repeated cycles. If you use boilers that do not adjust, it is better to use the next boiler when the capacity of one boiler is full, instead of disconnecting and connecting several boilers that are loaded. On the other hand, in regulating boilers, the efficiency of the boiler increases in the load-sharing situation. Therefore, using several boilers at the same time in load sharing mode is more beneficial than using one boiler with % efficiency. Figure shows the relationship between ignition rate and efficiency in boilers with adjustable air and fuel flow utilization.

Figure shows the combustion efficiency chart for natural gas fuel with electricity, which shows the relationship between excess air and flue gas temperature with combustion efficiency. For example, by following the Step line in the diagram, the amount of oxygen at % in the flue gas (as shown in the diagram equals approximately % of the excess air) and ° F as the flue gas temperature rises, the corresponding combustion efficiency is about . % is observed. At the same increase in the flue gas temperature by degrees Fahrenheit, the Step line shows that reducing the oxygen in the flue gas to % increases the combustion efficiency to about .%. The lower the percentage of oxygen in the flue gas, the less heat is transferred to the excess oxygen, resulting in increased fuel efficiency. The higher the efficiency, the more heat will be transferred to the inlet water instead of to the flue gas, thus reducing the flue gas temperature.

This type of pot or boiler is made up of connecting cast iron pieces called fins. Due to the ability to assemble and disassemble the cast iron boiler, it can be used in spaces where it is not possible to use a steel and integrated boiler. In fact, cast iron boilers are assembled and installed in the engine room. types of sections are used in the construction of each capacity of cast iron boilers, which are as follows.