Oil Fired Boilers

How they work:

Its better to think of your boiler as three parts Heat Exchanger Control Burner

The burner fires flames at the water filled radiator and the water gets hot. When the water is hot, the control switches off the burner.

Heat Exchanger The bulk of your oil fired (kerosene / 28sec) boiler is a steel box so they are very heavy. The box is know as a heat exchanger because it passes heat from the burning oil to the water passing through the jacket. After the heat passes the water filled jacket it exit to the flu (chimney).

Control The most basic boilers will just have two thermostats. One thermostat to control the power to the burner (control stat) and one to stop everything if the boiler overheats (safety stat). If your boiler is a combi type then it will also have a flow switch to control the position of a priority valve. The priority vale takes warm water in from the boiler heat exchanger and feeds it out to the radiators. If a hot water tap is used then the flow switch allows electic to the valve and it changed postion. The water from the heat exchanger is now flowing through the hot water heat exchanger and heating the tap water. Some boilers may have built-in timers or programmable clocks to set the boilers on and off times. The burner unit often operate with its own sub-control system that operates independantly to the boiler.

Burner When the burner receives power from the boiler it will start to operate. The normal control flow for the burner is: Main motor starts to rotate driving the fuel pump and blowing air into the boiler heat exchanger. Next the spark plug (electrodes) are powered with 10.000 volts and begin to spark The fuel control valve is opened electrically via a solenoid and fuel at around 100 psi flows to the burner nozzle The burner nozzle atomises the fuel and sprays a cone of misted fuel close to the spark. The spark ignites the fuel and a clean combustion occurs thanks to the air being forced into the burner chamber. An optical electronic device tries to sense the bright burning flames and allow the burner to continue running if light is detected. If the burner fails to ignite the burner will stop and a reset button will illuminate.