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3 Things to Know About Condensing Furnaces

Admin • Feb 20, 2019

Natural gas remains one of the most popular fuel sources for home furnaces. While gas furnace technology has mostly remained the same over the last several decades, manufacturers continue to experiment with ways to improve overall performance. As more homeowners express concern about rising energy costs, furnace efficiency has become a hot topic.


For optimal energy efficiency, no furnace can rival the performance of a condensing furnace. Unfortunately, many people remain unaware of the unique attributes of condensing furnaces. As a result, they overlook the benefits of upgrading to this technology. This article seeks to improve your knowledge of today's HVAC world by discussing three key things to know about condensing furnaces.



1. Condensing Furnaces Have the Best AFUE Ratings

In an effort to quantify performance attributes, all furnaces receive a rating known as annual fuel utilization efficiency, or AFUE for short. An AFUE rating, expressed as a percentage, tells you how much of your fuel's potential heat a furnace can capture and deliver to your home's air.


In this regard, AFUE differs from more technical ratings such as thermal efficiency, which only tells you how much energy a furnace can convert when operating at peak efficiency. AFUE provides more beneficial information for homeowners, since it paints an average picture of how well your furnace works over the course of a heating season.


Standard efficiency gas furnaces tend to have AFUE ratings between 78 and 84 percent . Most condensing furnaces, by contrast, have AFUE ratings between 90 and 97 percent . This improvement means that, for a given quantity of fuel, your furnace delivers 12 to 13 percent more heat to your home, thus lowering overall fuel consumption.


2. Condensing Furnaces Contain Two Heat Exchangers

All gas furnaces contain a component known as the heat exchanger, whose job involves passing heat to your home while keeping toxic exhaust gases safely isolated. As a mixture of natural gas and air ignite in your burner chamber, the hot gases produced flow into the heat exchanger, which consists of a snaking metal tube.


Meanwhile, air from your home moves around the outside of the heat exchanger, absorbing heat through the metal walls. Once the exhaust gases have reached the far end of the heat exchanger, they rise upward out of your home through the flue pipe, safely dispersing into the open air.


Standard furnaces often struggle to capture all of the heat produced in the combustion chamber. Instead, a percentage of that heat passes up out of your house along with the unwanted exhaust gases. This unintended heat loss explains the lower AFUE rating of a standard gas furnace.


A condensing furnace solves this problem by incorporating not one but two heat exchangers: the primary and the secondary heat exchangers. The secondary heat exchanger simply gives the system a little bit longer to harness all of the available heat. In the process, the exhaust gases often cool down to the point that any vapor present condenses into water.


3. Two Types of Venting Systems Exist

A condensing furnace may contain one of two types of venting systems: a direct vent system or a non-direct vent system. Direct vent systems contain two vent pipes - one to conduct exhaust gases out of your home and one to guide fresh air down into your combustion chamber. The two pipes usually penetrate down from your roof directly next to one another.


Non-direct systems contain only a single pipe, used to vent the gases produced by your furnace. Instead of drawing fresh air in through a secondary pipe, the furnace simply gathers input air from its immediate vicinity. If you plan to locate your furnace in a garage, basement, or crawlspace, a non-direct system may work for you. Otherwise, you'll need to have a direct vent system installed.


For more information on how a condensing furnace can improve the efficiency of your home's heating, please contact the HVAC professionals at R & B Inc.


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