A furnace is an enclosed structure where heat is produced to warm the air of a home or building. Various heating systems exist to achieve this, the most common being gas furnaces, electric heat pumps or electric furnaces, and oil furnaces.
The Basic Process Furnaces Use to Heat Your Home:
STEP 1: The furnace is heated using its primary fuel source being ether heat, gas, electricity, or a combination of these.
STEP 2: The heat energy produced by the fuel source is then used to heat the furnace heat exchanger. Any excess heat exhaust created in this step is released through the furnace's flue.
STEP 3: Your furnace then operates to pump out the cold dense air from your home through the ductwork into the looped tubes of the heat exchanger to warm the air.
STEP 4: The air is now heated and ready for the furnace blower to redistribute the air back to the rooms in your home.
Types Of Furnaces Systems
Gas Furnace
Gas-powered central air systems are the most common type of furnace. Natural gas is often the fuel that is used for this type of HVAC heating. These systems are made up of a gas valve, burners, a blower, a heat exchanger, a control system consisting of the thermostat and electrical controls, a ventilation system, and ductwork. They operate by using gas to heat the heat exchange in the furnace to heat the air of your home. Gas furnaces come in three varieties, single-stage furnaces, two-stage furnaces, and modulating furnaces.
Single Stage Gas Furnace
A single stage furnace is the most common type of gas heating system. Single stage furnaces have only one high gas flow setting when the gas valve is open. This makes these systems less energy efficient with an annual fuel utilization efficiency (AFUE) rating of about 80%. These systems are a better choice if you have a home located in an area with more mild temperatures.
Two Stage Gas Furnace
Two-stage furnaces are capable of fluctuating between high power and half power or low and high gas flow. These systems work closely with your thermostat to determine the amount of gas needed to sufficiently heat your home, which makes them more energy efficient than single stage furnaces with a general AFUE rating of 90%.
Modulating Gas Furnace
The most energy efficient type of gas heating system are modulating gas furnaces. These systems have an exceptional ability to determine needed gas usage with great precision by regulating output by one percent intervals. Modulating gas furnaces evaluate and adjust energy output by the minute, ensuring the output of gas energy is limited to the minimal amount needed to provide your home with optimal warming comfort. A modulating gas furnace can achieve an astounding AFUE rating of up to 98% efficiency!
Hot Water Boiler Heating
A boiler also works to heat your home with gas, only it does so through the use of radiators placed throughout your home which have gas heated water flowing through them. Boilers work by releasing gas through a gas valve into a sealed combustion chamber in the boiler through small jets. With an electrical ignition, the gas is combusted to create heat. This heat is absorbed by a connected pipe carrying cold water. The water is heated to about 60°C (140°F) and transferred to the radiators through your home to maintain the heated indoor climate you desire.
Oil Furnace
Oil furnaces are fueled by heating oil, a low viscosity, liquid petroleum product. In oil heating systems, the process begins in the combustion chamber where oil is electrically ignited to heat the furnace heat exchanger. The heat is then transferred to the gas or boiler water that your oil HVAC heating system uses to heat the air that will be distributed through your home.
Electric Furnace/Heatpump
Heat pumps are electric-powered machines that warm your home by pulling in cold air and sending the air through the refrigeration cycle. The air is heated and then redistributed throughout the rooms of your home.
Electric furnaces, or heat pumps, consist of the following indoor and outdoor parts:
Heat Pump Out-Door Parts:
- A condenser that heats or cools the air, depending on which way the refrigerant flows.
- A defrost control board with a sensor that automatically runs a defrost cycle when it detects frost and ice. If steam is rising from the outdoor unit, that likely means it is defrosting.
- A compressor that pressurizes and moves the refrigerant fluid through the system.
- An electric heat strip for auxiliary heat.
- Refrigerant lines that connect the outdoor unit to the indoor unit.
- A fan that pulls in air.
Heat Pump In-Door Parts:
- Thermostat control.
- Ducts and vents that distribute air through the home.
- An air handler made up of a blower motor, evaporator coils, and a fan that moves warm air into the ductwork.
- A condenser that heats or cools the air, depending on which way the refrigerant flows.