A Complete Guide to Heating Systems

We typically don’t think much about how our heating system works, as long as it provides warmth and comfort. However, when a furnace breaks down on a bone-chilling day, it’s a stark reminder of the importance of understanding how heating systems operate. Having basic knowledge about your system – such as recognizing signs that it needs repair and understanding the benefits of regular maintenance – can help keep it running smoothly for years to come.

HVAC.com’s comprehensive guide to heating systems explains the different types of heaters, how they work, and their major components. You’ll also learn how to choose a system that fits your home and budget, and why maintenance is crucial for efficiency and longevity.

How Do Heating Systems Work?

Heating systems provide warmth by using a fuel source like natural gas, electricity, oil, or renewable energy. The most common type is a forced-air system, where a furnace heats air and blows it through ducts and vents to warm the home. The furnace either burns fuel or uses electricity to heat the air, and when the thermostat senses the room has reached the desired temperature, it signals the furnace to stop.

In a gas or oil furnace, the heat exchanger plays a key role: it transfers heat from the burning fuel to the air without allowing combustion gases to mix with the heated air. In electric furnaces, the heat exchanger still helps to efficiently distribute warm air, but without combustion. Whether fueled by gas, oil, or electricity, the heat exchanger ensures that heat is transferred safely and efficiently, helping to maintain optimal indoor comfort.

Hydronic heating, another popular type of heating system, uses a boiler to heat water, which is circulated through pipes to radiators or underfloor systems. These systems release heat into the air to maintain comfort. Meanwhile, heat pumps, which transfer heat from the outside air or ground into the home, are energy-efficient systems that can also cool your space. They are growing more popular due to available HVAC tax credits that are aimed at reducing carbon emissions.

Thermostats regulate the temperature by sending signals to the heating system to turn on or off as needed. Regardless of the type of heating system, they all are designed to distribute heat evenly and efficiently to ensure comfort while minimizing energy use.

The Different Types of Heating Systems

In all heating systems, the primary heating appliance is usually located in the basement, attic, garage, or mechanical room. Heat pumps are located outside and are paired with an indoor air handler.

• Furnaces: Most U.S. homes use a furnace to heat air, which is then circulated through ducts. Furnaces can be electric, gas-fired (using natural gas or propane), or oil-fired. Electric systems use electric coils to generate heat, which is then circulated through the home.
• Heat Pumps: Heat pumps run on electricity and transfer heat between the inside and outside of the home. They can be air source or geothermal:
  • Air-to-Air Heat Pumps: These are the most common, transferring heat between the home and the outside air. Modern models work efficiently even in cold climates. Heat pumps have a reversing valve that switches the direction of refrigerant flow depending on whether the system is in heating or cooling mode.
  • Geothermal Heat Pumps: Geothermal systems use the stable temperature of the earth or a water source to heat and cool the home, making them highly energy efficient. Geothermal heat pumps are one of the most expensive HVAC systems to buy and install because they require digging deep trenches and burying underground loops of pipes, making it a complex and labor-intensive project.
• Boilers: Boilers use combustion to heat water, which is then distributed through pipes to radiators or underfloor heating systems. Steam and hot water boilers are the two main types, with hot water boilers generally being more efficient.
• Hybrid Systems: Hybrid systems (sometimes referred to as dual fuel systems) use both a heat pump and a furnace, switching between the two for optimal efficiency. Although some modern heat pumps can operate in temperatures below zero, older systems lose efficiency once the temperature dips below freezing, making a furnace a more efficient option during extreme weather.
• Radiant Heating: Radiant heating systems provide heat through the floors, walls, or ceilings, directly warming objects and people in the room without relying on air circulation. Radiant systems can be powered by electricity, water, or air.

Heating System Trouble Signs

Knowing when your heating system needs to be inspected by a professional can help reduce the chance of a significant and costly repair. Here are some common signs your heating system may need attention:

• Age: If your system is over 15 years old, it’s time for an inspection. Gas furnaces typically have a lifespan of about 15-20 years, while electric units can last about 20-30 years. Meanwhile, heat pumps and boilers have a lifespan of about 15 and 15-20 years, respectively.
• Lack of Hot Air: If the furnace isn’t producing enough heat, there could be several issues at play, including incorrect thermostat settings, issues with the gas supply, a pilot light that is out, leaking ducts, and a cracked heat exchanger. However, the issue could be as simple as a clogged air filter that needs to be replaced, so start by checking the filter before calling an HVAC technician.
• Strange Noises: Persistent or unusual sounds like squealing, rattling, or grinding may signal a mechanical issue – such as a worn-out blower motor or loose components – that requires professional attention.
• Rising Energy Bills: A sudden increase in heating costs could mean your system is struggling to maintain your desired temperature. Common causes of high heating bills include an aging system that is struggling to keep up with your home’s heating demands, air leaks, a clogged air filter, or a lack of maintenance.
• Short Cycling: Furnace short cycling occurs when the system frequently turns on and off in short bursts, preventing it from reaching the set temperature. This can be caused by issues such as a clogged air filter, a malfunctioning thermostat, or an oversized furnace, all of which can disrupt the normal heating cycle and reduce efficiency.

Preventing Heat Loss and Improving Efficiency

Simple steps can prevent heat loss and improve your heating system’s efficiency:

• Schedule an annual inspection with an HVAC professional.
• Change furnace filters regularly (typically every 2-3 months).
• Ensure vents are unobstructed and windows and doors are sealed properly.
• Inspect for air duct leaks. Leaky air ducts can lose as much as 20% of conditioned air.
• Insulate your home to reduce heat loss and improve energy efficiency.
• Use weatherstripping to seal gaps around windows and doors to prevent drafts.

Heating System Maintenance

Regular maintenance is key to ensuring your heating system performs optimally and efficiently during the winter. A heating tune-up once a year – typically in the fall before you turn the system on for the first time – can ensure everything is operating properly. A technician can also identify any minor issues and recommend the needed repairs.

An HVAC company will typically perform the following steps during a furnace tune-up:

• Inspect the furnace: Look for signs of wear and tear or damage, focusing on key components such as the heat exchanger, burners, and ignition system.
• Check Thermostat Settings: A technician will inspect and calibrate the thermostat as part of regular maintenance and ensure it’s set correctly.
• Inspect Electrical Connections: Tighten any loose electrical connections to prevent safety hazards.
• Lubricate Moving Parts: Keep motors running smoothly by lubricating them to prevent excessive wear and tear.
• Clean Critical Components: 
• Check Gas Connections: Look for any gas leaks or other hazards that need to be addressed immediately.
• Replace Air Filter: Dirty filters can reduce efficiency and damage your system. A technician can inspect the filter and replace it with a new one, if necessary.

Does My Heating System Need to Be Replaced?

You should consider replacing your heating system if it is older than 15 years, although some systems such as gas furnaces and boilers may last as long as 20 years. Aside from the age, your system may need to be replaced if it needs frequent repairs and your energy bills have steadily increased.

Although replacing an HVAC system may seem like a significant financial investment, most companies offer financing options to make the payments more affordable. Utility rebates and tax credits may also be available if you’re considering a high-efficiency system.

If you’re looking to replace your heating system, contact HVAC.com. Our friendly advisors can walk you through the process, provide a quote, and connect you with a reputable dealer in your area.