Difference Between a Heater, Furnace, and Boiler

In the middle of this frigid winter, you may wonder what device is causing your living room to maintain that comfortable 72 degree temperature. Most homes are equipped with a central heating system, though the parts that make up that heating system can be a bit confusing. What is my heating system, and how does it function?

Hauser Air will take you along for a look at the definitions of heaters, furnaces, and boilers, and how they actually work.

1) Heaters: The Basics

Carrier Heater

Defining the term heater is quite tricky. A heater is really just a catch all term for a device that heats up an environment. Central heating as we know it today got its start in the Roman Empire. The Romans would have an underground source of combustion which would be distributed by holes in the ground and pipes along the walls. After the fall of their civilization, western heating technologies reverted to more primitive fireplaces for nearly a thousand years.

Central heating units tend to have a location for the heating device, be it in a machine room or attic or basement, where the heat is created and distributed throughout the building. These are quite common in most houses, apartment complexes, and commercial buildings. Modern central heating systems are efficient enough that they typically won’t require additional energy-wasting localized or space heaters.

A central heating system uses some form of energy combustion or release, be it from a furnace or furnace and boiler combination. What are furnaces and boilers? Essentially, a furnace or boiler is the mechanism that produces the heat that your central heating system will then distribute to keep your home warm. A central heating system without a furnace and/or boiler wouldn’t be much of a heating system at all.

2) Furnaces: Giant Boxes of Fire

Ion 96 Variable speed gas furnace N95ESN

Furnaces get their name from the Greek word “fornax,” which means oven. The first furnaces were stone or clay structures that used coal and/or wood to create intense heat. These furnaces were primarily used for ceramic work, such as with kilns, and smelting ore to create metal objects, tools, and materials. They are still the primary appliance in industrial metal production.

Industrial furnaces are, simply put, cages for raging fires that are hot enough to melt stone, and sometimes, like the image above, look like something built to haunt small children.

Eventually the furnace, with its heavily concentrated combustion in a box, would be applied to the home as a more efficient form of heating versus stuffing open fire underneath flooring.

Modern day home furnaces tend to run off gas or electricity or induction (a reaction of electricity and metal to create heat). They are much safer and contained than their older counterparts, and are the cornerstone for most modern central heating units, producing high amounts of heat that feed into a ventilation system and flow throughout all of the connected rooms.

Small furnaces, usually electrical, are often attached to boilers and water heaters to apply the necessary energy in order to give us hot showers and scalding sink faucets, or even to circulate heat from the boiler to heat our home.

Speaking of boilers…

3) Boilers: Using Water for Warmth

Technician servicing a boiler unit

A boiler’s job is to turn water into steam, which is denser than air and lighter than water. Air doesn’t hold heat as well, and water is difficult to move, so steam is a good medium for transferring heat to where it’s needed. In most instances, a small furnace or heating device is attached and provides the heat to get the water steaming. Boilers, like furnaces, are not just used for home application.

Boilers date back to the 1700s, emerging from the early days of steam experimentation. They were, and in some instances still are, used for transportation and machine power. Steam locomotives, steamboats, and steam industrial manufacturing machines all ran off the use of boilers. The boilers produce steam with the help of wood or coal furnaces and the steam is fed through a series of pistons and tubes to create movement, making wheels turn and tools hammer and assembly lines move.

After the discovery of electricity, boilers and steam-generated electricity became the common source for electrical power. Even today most power plants use boilers and steam generators in conjunction with coal, natural gas, and nuclear fission to provide the energy for the device you are reading this on.

In home use, boilers can act as a kind of go-between with a furnace and your heating set up. Often a smaller gas or electric furnace is attached to the boiler, heats the water, and once the water has hit its boiling point, the heat is distributed through a series of pipes and ducts that make up your central heating system. This process is also applied to your water heater providing the warm water you need for washing clothes and dishes. Using a boiler can eliminate the need to have a separate traditional central heating system and hot water heater, and are highly efficient due to the fact that the steam is in a closed loop that recycles steam back into water to be boiled again.

Heaters, Furnaces, and Boilers are all connected

If a heater is a broad term for the mechanism applied to heat a home or business, then a furnace and boiler are the specific appliances installed to accomplish that goal. Most homes have a boiler and a furnace to some degree. The furnace is the primary source of central heat, pumping hot air into every room and kicking the cold to the wayside. The boiler is supplying the hot water for morning wake-up showers and scrubbing pots clean. They function on different processes but require each other to provide the comforts we have all become accustomed to. The question of if a furnace or boiler is better for heating really comes down to the age of the building and personal preference. In the end, all that matters is that we’re able to be comfortable in whatever building we’re in and not freezing, and thanks to the evolution of the heating industry.