From time immemorial, from the day man invented the art of making fire by striking two flint-stones that can produce fire out of friction, fire has become the part of life; more so when he learned to tame the flame and started to use the fire to his advantages.
Furnace has been occupying an indispensable roll in domestic process heating system and household furnace has become an appliance installed to provide process heat.
Originally designed to heat the space inside the home, either by direct radiation from fireside or by heating fluids like air, water or steam and moving them through heat transferable conduit material, furnaces find their application invariable and indispensable in countries of cold climate.
Fuels that find place in domestic furnaces are LPG (liquefied petroleum gas), natural gas, fuel oil, coal, wood or other hydrocarbons that can give heat when burnt.
Where electricity is economical, electrical resistors are used to convert electrical energy to heat energy and the heat thus created is employed for process heat application.
Recent development is to use electromagnetic system to create electrical induced heat that is used in induction heaters.
When external combustion is employed, there should be a chimney to expel the hot gases and most portion of the heat thus generated resulting in fuel loss and heat loss.
But high tech high efficiency furnaces are designed to make use of this out going stack heat and radiated inside the room space of the house by some mechanical means.
Condensing and non-condensing furnaces are classified so on the basis of their efficiency, in the heat recovery from exhaust gases.
Condensing furnace is the one that utilizes the hot gases of the exhaust, which may contain water vapors and other toxic chemicals.
To prevent the corrosion due to these condensates, a condensate pump is employed to remove this condensate accumulation.
This normally claims back about 35% of heat that would have otherwise been wasted.
The furnace essentially consists of three major systems of operation as integral components.
They are: the heat generating system, controls and safety devices and the blower and hot air movement system.
A burner is involved in spraying the fuel and aiding the combustion of the air fuel mixture thereby aid in establishing the flame.
Flame that is established is heat itself in a form, is pushed to places to be heated, which is regulated by the control devices.
To prevent any mishap by over heating or by over pressure safety devices are there arrest the ongoing process.
The whole process could be made automatic by adequately providing automation switches.
There are various modern solutions are available to complement this.
Sequence controller is one such equipment which will control all the ongoing process by commanding operation switches like blower, fuel pump, burner related solenoid valve, spark plug and spark inducing transformer, photocell that senses the flame and co-ordinate their works.
The proceedings are controlled automatically with this miniature computer and the process heat production is modulated.
Thus, a furnace fulfills the need of domestic process heating safely and satisfactorily.