Furnace Replacement Basics: When It’s Needed and How to Choose Your Next System

Published on: April 16, 2014
Man repairing a furnace | AC Southeast®

A residential furnace can be expected to give you 15 to 20 years of reliable performance in heating your home. However, even the sturdiest and best-maintained furnace will eventually start to lose efficiency and performance. When it reaches a point where it costs more to run or repair the system than it’s worth, or when the furnace just breaks down entirely, it’s time to consider furnace replacement.

At the outset, this may seem like a complicated and expensive process. In reality, furnace replacement can be relatively easy with some basic knowledge and insight into your options. Here’s a brief guide to furnace replacement that can help you with the information you need to make a wise and economical choice of heating equipment.

Telltale Signs Indicating Furnace Replacement

Most homeowners will want to get all they can out of a furnace before replacing it. Regular preventive maintenance, filter changes, and prompt repairs will keep the system working at its best for as long as possible. Keep in mind that the age of a furnace should be a consideration when making the decision to replace it, but should not be the only criteria used. A 20-year-old furnace in good condition should still give you a few more seasons’ worth of heating. Whatever its age, when the equipment starts showing some of the following signs, a furnace replacement may be a better option than another repair.

  • Decreased reliability: You expect your furnace to work when you need it, but if the system is breaking down often or not producing enough heat, it could mean a replacement is due soon. Furnaces will typically break down more often during the last two years of their functional lifespan. Multiple repairs over the last couple of seasons means a replacement may be needed.
  • Loss of efficiency: A sudden sharp increase in your heating bills could indicate the furnace is losing efficiency, using more fuel or electricity to keep up with indoor temperature demands. An inefficiently operating furnace is more likely to fail during the stresses of peak seasonal use.
  • Inconsistent or uneven heating: A furnace should produce enough heat to keep all areas of your home at a relatively consistent temperature. Uneven heating, rooms that are hotter or colder than expected, or lack of heating in some areas can indicate a furnace that needs replacement.
  • Loud or unusual noises: Furnaces will usually produce some minor noise when operating, particularly sounds of fans blowing, air moving through the ductwork, or burners igniting. When the system produces loud noises or sounds you’ve never heard before, the system may be on the verge of failure.
  • Change in burner flame color: Gas and propane furnaces will have a burner that ignites fuel to produce heat. Normal burner flames should be blue. If the burner flames change to yellow, it could indicate the presence of carbon monoxide, which is a dangerous exhaust gas produced as a byproduct of combustion. Have this checked immediately; carbon monoxide is deadly and, if it leaks into your home’s living areas, could be a threat to life and health. If the problem is caused by a cracked heat exchanger, it is often less expensive to completely replace the furnace than to fix the broken part.

Types of Furnaces

You have several options when choosing appropriate equipment for furnace replacement. It’s very likely that you’ll want to replace your furnace with one that’s similar to and uses the same fuel as the one you already own. However, if you want to switch to a different type of fuel source, you can easily find a new system that meets your requirements.

  • Gas: Gas furnaces are very common and readily available. They use natural gas as their fuel source. The gas is usually provided by local utility companies that provide pipelines and permanent connections to an ongoing source of fuel. You can find newer gas furnaces that are highly efficient and economical to operate.
  • Oil, propane and other fuels: There are several types of furnaces that burn oil, propane, and other types of combustible fuel to produce home heating. Fuel for these types of furnaces does not typically come through a local utility company. Instead, it is kept in a large storage tank installed inside or near your home. A local supplier will refill the tank as needed. Keep in mind that tank refills can be a significant expense; if you’re used to making monthly utility payments, this could require a change in budgeting.
  • Electricity: Electric furnaces are powered by electricity. They can be extremely efficient and effective sources of home heating. Since most homes already have connections to an electricity supply, these types of furnaces are appropriate for almost all situations.
  • Heat pumps: Heat pumps work by capturing heat and moving it from place to place. Air-source models pull heat from the air, while geothermal systems collect heat from the ground. The heat is then moved from the outdoor source and into your home. In the summer, heat pumps provide cooling by absorbing heat from inside your home and dispersing it outdoors. Heat pumps tend to be more expensive than furnaces, but their high efficiency and reliability mean they cost much less to operate.

Considerations Affecting Furnace Replacement

  • Sizing: A furnace must be properly sized to provide the amount of heating that you require. Size, in this case, refers to functional capacity, not physical dimensions. If the furnace is too small, it won’t produce enough heat and will wear out sooner from overwork. If it’s too large, it will generate too much heat and waste energy and money. Before investing in furnace replacement, have your HVAC contractor conduct a heating load calculation on your home. This analysis will assess physical and thermal characteristics of your residence and, with the aid of sophisticated computer software, will tell your HVAC expert the structure’s heating requirements. From there, a properly sized furnace can be identified. Make sure that load calculations are conducted using industry standards such as Manual J, “Residential Load Calculation,” published by the Air Conditioning Contractors of America (ACCA).
  • Efficiency: Efficiency ratings indicate how effective the furnace is at converting fuel into heat. This will have a significant impact on how much you spend on residential heating each month. Higher efficiency furnaces will produce excellent levels of heating at a relatively low cost. The efficiency of a furnace is indicated by the unit’s Annual Fuel Utilization Efficiency (AFUE) rating. The AFUE number denotes the percentage of the energy in the fuel used by the furnace that gets converted to usable heat. An AFUE 90 gas furnace, for example, turns 90 percent of the energy in the gas to heat, while the other 10 percent is lost through heat dissipation or exhaust. Higher AFUE ratings mean higher efficiency levels. Heat pumps and some electric furnaces can achieve AFUE numbers in the mid-90s.
  • Government efficiency standards: You can also look for indicators of compliance with government efficiency standards. The most common of these is the Energy Star label. The Energy Star program is an education and conservation initiative of the U.S. Department of Energy and Environmental Protection agency. When a furnace displays the Energy Star label, it means the unit has been tested and certified to be as energy efficient as possible.
  • Efficiency boosters: You can choose to include several types of additional components that will boost the efficiency and performance of your furnace even further. Variable-speed blowers operate at different levels depending on heating demands, which means they will work most often at a lower money-saving speed. Dual heat exchangers provide an additional heat exchanger that extracts additional heat from the system’s exhaust gases, recovering this heat before it is lost to exhaust process. Programmable thermostats give you options for precise control of the furnace’s operation, letting you automatically reduce operation when less heating is needed.
  • Air filters: The air filters in your furnace capture and hold particulates in the air circulating through the system. They are important components of furnace operation and indoor air quality. Make sure you use a filter with an appropriate MERV (Minimum Efficiency Reporting Value) rating, which indicates furnace efficiency. MERV numbers range from 1 to 16, with filters in the middle of that range providing the best combination of effectiveness and economy.
  • Installation: Expert installation by a licensed and certified HVAC professional is essential for safe and effective operation of your home heating system. Professional installation is especially important for furnaces that burn combustible fuel. If not installed properly, these systems could cause fires or explosions, or be responsible for carbon monoxide leaks that could harm or even kill occupants of your home. Check contractors’ licensing and certification status with your state’s licensing board and ask to see credentials before hiring.

Replacing your older, inefficient furnace with a newer, more efficient model will pay off with better indoor comfort and reduced energy bills. Contact us today for help finding a contractor who can advise you on furnace replacement and can sell, install, and service your new furnace.