Classifying Furnace Based On Different Parameters

A comfortable house is warm and inviting. One of the things that ensure this is heating system of the house. It is the heating system that will make you cosy and warm on chilling winter nights. Consequently you should have a good a furnace system in your premises. Furnaces are of various types. We select them on the basis of our need, budget, location etc. Let’s take a look at the types of furnaces -

Central Warm-Air Furnace: In this type of configuration there is a central unit which may be combustion-based or working on a resistance heater. The unit may run on gas, oil or electricity. The central system produce hot air which is circulated throughout the house through a forced-air system or gravity based mechanism. In forced-air system a blower fan is used to propel the air through the ducts. It goes out in the rooms through registers that are fitted at the end of the ducts. Once the temperature of the air falls in the room, the air comes out through the return ducts to the central heating system to get heated again.

The gravity furnace works on the principle that warm air rises and cool air falls. These do not depend on blowers to circulate the air through ducts and vents. The air produced by combustion chamber rises through ducts and the cold air falls through ducts that return it to the furnace to be reheated, thus completing the circulation cycle. This is a very old design of furnace and also called the octopus furnace.

Steam or Hot-Water System: In this the central furnace system instead of producing hot air produces steam or hot water. The hot water or steam is conveyed thorough conventional radiators, baseboard radiators, convectors, or heating coils or pipes embedded in the walls or ceilings, or are inlaid in a concrete slab floor

Heat Pump: Heat pumps draw heat from the exterior environment and move it into the house to cool the rooms. The pump can heat the house both through forced air system as well as hydronic hating. There is refrigerant circulating in the coil of its outdoor unit that absorbs the heat from exterior environment. The refrigerant is compressed at a high temperature and pressure and condensed at the coils of the indoor unit. The heat that is given out is used to warm the rooms. The pump can also reverse its cycle to cool the house.

Pipe-less Furnaces: The furnace that we discussed of are all dependent on ducts to provide heat. Furnaces can be pipe-less as well. In these a combustion or resistance unit kept in an enclosed chamber. They burn the fuel or generate heat through a resistance heater. They can be located below the floor to heat the room immediately above. They can also be located in walls. Sometimes these are installed in a basement and delivers heated air through a large register in the upper floor of the room.

Furnaces can also be classified based on the fuel they use. In this regards they are classified as electric furnace, gas furnace or oil furnace. We will do a comparative study of the furnaces.

Installation Costs

The installation charges of electric furnaces are the least. This is because you do not need to have fuel lines or exhaust system for these. The oil or gas furnace would need fuel line for the fuel to come and get com busted in your furnace. You will also need to have proper chimney or a vent system to give out the exhaust air and prevent back drafting. The gas and oil furnaces also need big storage spaces as well as some electrical wiring.

These all add up to greater initial installation expenses for propane and fuel oil.

Operation Costs

This will depend on the cost of fuel and electricity that varies from place to place. In some areas electricity is cheaper than fuels, in other areas the case may be just the reverse. So know the fuel as well as power prices in your locality to determine which fuel source is the best buy.


In terms of efficiency it is the electric furnaces that win. They nearly use 100 percent of the electricity to convert it into heat. In combustion furnaces there is always loss of energy when gas or oil is being converted into heat. This loss can range from 5 percent to 30 percent. When buying a furnace always check out its efficiency ratio. This is found on the furnace la belling.


The gas furnace or oil furnace always produces some emissions. The electric furnaces are without any harmful emissions. However the plants that produce power give out toxic emissions. So choose a furnace based on how electricity is generated in your area. If you can avail green electricity then using electric furnace is fine.

Besides this furnaces can also be classified as single-stage, double-stage and multi-stage furnaces. The single stage furnaces are also known as single speed furnaces. They have one stage of heat output, which is high. They give out maximum heat that they are capacitance for in all weather conditions. The double stage furnaces have two speed limits. At most weather conditions, it works at 65% of its efficiency. When the outside temperature drops down way low, it increases its speed and works at its full efficiency. In variable speed furnaces, the fan motor can move at different speeds to control the amount of heated air dispersed throughout your home. It controls the humidity better and allows a better airflow.



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