Heating System Components

Knowing how your heating system works not only helps when talking with a technician, but also helps you understand the importance of having your HVAC system inspected and maintained each year to keep it running efficiently.


What is a furnace? Simply put, a furnace draws air in from the living space, heats it up and returns it to warm the home. Most furnaces use gas—either natural gas or propane—ignited by the pilot to warm the air. Electric furnaces use heating elements, or strips, instead. Both types of fuel options result in the warm air being blown into the living space through ductwork.

There are a few types of furnaces, depending on your home and where you live.

Upflow furnace

An upflow furnace takes cool air in from the bottom and discharges it from the top. These are generally placed in the home’s basement. Because hot air naturally rises and cold air sinks, upflow furnaces have to perform less work and tend to have longer life spans than the other configurations. However, if you have no basement or crawlspace, an upflow furnace is not an option.

A gravity furnace is a type of upflow furnace that does not use a blower motor, but instead uses physics—the heated air rises through ducts and cooled air sinks through return vents.

Horizontal flow (or cross-flow) furnace

A horizontal furnace lies on its side, pulling cool air from one side and pushing warm air out of the other. Horizontal furnaces are often used in locations where there is limited space and may be found in a crawl space or a closet.

Downflow furnace

In this configuration, the furnace takes cool air from the top and discharges warm air from the bottom. Downflow furnaces are generally found in homes with no basement and are usually placed in an attic.

No matter what type of furnace you have, be sure to have regular maintenance performed to help extend the life of your furnace. Air filtration is critical to effective heating, so change your filters often and have your furnace professionally serviced before every heating season.

Call 866-399-2885 to set up an appointment with your local ARS®/Rescue Rooter® heating specialist if you have questions about your system.

Boilers and Radiators

Some of the most common heating systems in newer homes are hot water heat and steam heat, two types of “sealed water-circulating systems” that circulate water heated by a boiler through pipes to radiators.

With regular use, it's only natural that these systems will need maintenance to run smoothly. Here are a few maintenance tips that may reduce the amount and severity of boiler and/or radiator repairs. Most of these should be performed by a professional.

Bleed your hot-water system

At the start of each heating season, you will need to bleed your system of unwanted air. While the system is running, go from radiator to radiator and open each bleed valve slightly, then close it when water starts to escape. For multi-level homes, start at the top floor and work your way down.

Zoned heating systems

Save energy by retrofitting separate controls for different zones in large homes, such as areas that are not used often or are on a different schedule than the rest of the home.

Insulate pipes

In steam and hot water systems, insulating pipes is cost effective because it avoids dissipating heat in unwanted areas. Install fiberglass pipe insulation that can withstand the high temperatures of these delivery pipes.

Steam heating system

Steam radiators also need regular maintenance. A clogged air vent will keep a steam radiator from heating up, and usually needs to be replaced. If you notice one of your radiators is not heating up, you should contact a heating specialist to check the air vent.

Banging radiators

Steam radiators can warp floors and dig ruts, causing the radiator to tilt and creating banging noises when the radiator heats up. Shims should be inserted under radiators to pitch them slightly toward the pipe in a one-pipe system or toward the steam trap in a two-pipe system.

Reflect heat for efficiency

Installing heat reflectors behind radiators on exterior walls helps prevent heat loss and lowers energy costs. Simply make your own reflector from foil-covered cardboard or by mounting foil onto a foam board. The foil should face away from the wall and be the same size as the radiator.

Contact your local ARS®/Rescue Rooter® heating specialist at 866-399-2885 to learn more about radiator and boiler repairs and maintenance.

Air Handlers

An air handler is the indoor unit that provides conditioned air circulation through your home.

An air-handling unit includes a blower, heating and/or cooling elements, filter racks or chambers, and dampers. Air handlers usually connect to ductwork that distributes the conditioned air through the building and returns it to the air handler.

If you have a forced air furnace, the air handler is the part that blows the hot air out. It probably also circulates cooled air from your air conditioner.
If you don’t have a furnace, you may have a stand-alone air handler to blow cool air from your air conditioner and/or hot air from your heat pump through your home’s ductwork.

Changing your filters regularly is the key maintenance for your air handler, whether it's part of your furnace or a stand-alone unit. You should also have your entire HVAC system inspected and maintained by a professional each year to make sure that any potential problems are caught before they become big.

Call 866-399-2885 to set up an appointment with your local ARS®/Rescue Rooter® heating specialist if you have questions about your heating system.


The thermostat is the remote control for your home's heating and cooling systems. It works to control your system and deliver the exact room temperature you desire. There are two basic types: electro-mechanical thermostats and digital thermostats.

Electro-mechanical thermostats

Electro-mechanical thermostats are the older types with little metal coils and a mercury tube inside. As the temperature in a room shifts, the coils either contract or expand, pushing the mercury to one end of its tube or the other which signals the HVAC system to either turn on or off.

Digital thermostats

Digital thermostats are much more accurate at keeping your home comfortable. Most models today are programmable thermostats, which means you can set times for your system to run or shut down. Because you have much more control, you can possibly save on your energy costs by reducing your heat and cooling when you don't need as much.

Call 866-399-2885 to set up an appointment with your local ARS®/Rescue Rooter® heating specialist if you have questions about your heating system.

Air Ducts

What most people don’t realize is that their equipment is only part of the solution. To fully feel the benefits of your heating system, your ductwork must be as well thought out—and maintained—as your HVAC unit.

Some new homes these days are being built with ductwork running through the conditioned living space. By constructing an insulated zone between the ceiling joists and a dropped ceiling, or between the walls mainly in the corners of a room, ducts can exist in a area where any lost air would contribute to the overall comfort of the home.

Of course you don’t have to build a new house to improve the efficiency of your ductwork. One thing you can look at is your duct’s configuration. A radial design, where air supplies and returns have direct connections to the unit, or a trunk and branch design, where supplies and returns branch off from a long “trunk” directly connected to the unit, are best for most houses.

Poorly planned or sloppily installed ducts can negate energy savings. Joints that aren’t sealed properly can allow a lot of that precious heated or cooled air escape—as can old ductwork that may not be up to par with today’s new standards. Even newer ducts, when placed in areas where temperatures can be extreme (like attics), release a not-too-insignificant percentage of that comfy air.

Call 866-399-2885 to set up an appointment with your local ARS®/Rescue Rooter® heating specialist if you have questions about your heating system and air ducts.