Source of Fuel
In these type heating systems, the source of fuel is oil. This oil is sometimes replaced with a blend that includes biodiesel. This use of biodiesel decreases dependency upon oil reserves and increases fuel consumption efficiency. This heating method is often found in the northeast sections of the United States as they may be limited in natural gas reserves.
In oil fired forced air heating systems there is an oil burner that throws a flame into a firepot or a combustion chamber. A thermostat controls the burner which will activate a pumping action related to the oil. This action gets the oil into the burner nozzle. When the thermostat calls for heat, it operates a relay. The circuit is then closed to the burner motor. A high voltage transformer is connected into the circuit. Sparks are then created that ark across a gap between two electrodes. Fuel is then sprayed from the burner nozzle. The spark causes an ignition of the fuel make a flame in the firepot.
There is a thermostat located in the exhaust stack of this heating system. If ignition does not take place, the thermostat will stop the pump. When the top or bonnet area of the system reaches the called for temperature, a blower is started. This blower is in the cold air duct.
A temperature control limit switch is located in the bonnet. It opens the electrical circuit and stops the burner if the temperature exceeds the called for temperature from the thermostat.
Retrofits and Efficiency
Common complaints related to oil fired heating systems centralize around the inefficient use of fuel in the combustion chamber. Essentially, too much fuel is used to keep the chamber warm enough for the cirulation of heat. Another loss of energy appears at the chimney where too much heat is lost through exhaust.
One retrofit that addresses a loss of usable heat is the replacing of the nozzle that directs combustion. This is called down-firing. Down firing involves the placement of a lower gallon per hour rated nozzle so that less fuel is used during each firing cycle. The combustion chamber might have to be resized and the fuel pump pressure may have to be adjusted.
In addition, the whole burner may need to be replaced with another flame retention burner. This burner will seal or block the airflow going into the chimney when firing is not taking place.
Forced Air Maintenance
When using a forced air system, it is important to know what maintenance or HVAC technicians will be concerned about when they are assessing your system. A thorough check will require they check for cracks in the combustion chamber. They will also evaluate and monitor the air for levels of carbon monoxide and provide a solution should one be needed. They will search to know if the blower requires adjustment. An assessment of the supply air temperature will be needed. They will remove dirt, grime, soot or any corrosion. The levels of fuel use must be determined to see whether or not the unit is efficiently using fuel sources. The burner and the size and duration of the flame must be evaluated and adjusted if needed. All seals between the combustion area and the ducts must be checked to ensure no leaks are present.