Natural Gas Furnace | Gas Furnaces
Gas Furnaces are one of the most common and efficient ways to heat a home and found in several types of Central HVAC split systems. The most common type matches three main components of the furnace, evaporator coil (in systems with central air conditioning) and outdoor AC condensing unit. Gas furnaces are also an integral part of the newest Hybrid heating systems! When your home reaches the temperature set on the thermostat, it makes a call for heat. That signal is sent to the gas furnace which begins the process of the furnace starting up and warming up the heat exchanger element inside. When the heat exchanger reaches a factory set point, the blower inside the system starts and begins to distribute the warm air throughout your duct system and to the home.
Types of Gas Furnaces
When you read about the different types of gas furnaces available, the one thing you want to pay the most attention to is the Gas Furnace Efficiency Rating, measured as AFUE. (Annual Fuel Utilization Efficiency) In the past, finding a furnace with 60-80% AFUE was very common. In recent years however, furnace efficiency has reached into the range of 96% AFUE on some of the better units! A good way to understand the efficiency rating, would be to equate it to a single dollar. For example an 80% AFUE furnace is designed to deliver .80 cents worth of heat, for every dollar of natural gas it burns. The remaining amount is wasted and exits through your flue, or chimney pipe. If you live in an area like the Northeast, where you use heat for 6-8 months out of the year, you should buy the highest efficiency unit you can reasonably afford. it may cost a bit more in initial cost, but will pay for itself within just a few years, if not sooner! A typical 2000 sf home in Vermont could save more than $400 in annual operating costs just by choosing a 95% unit, over an 80% unit! (Source: HVAC Op Cost)
Another main difference in the higher efficiency furnaces (+90%) is that are condensing furnaces. Since the gases get burned off twice, the main byproduct is water, versus smoke! This means they can be vented through regular PVC pipe, versus running metal flue pipe out of a chimney or dedicated flue.
Other common features found on Gas Furnaces
- Variable Speed Fan Blowers
- Multi-Stage Burners
- Humidification Control
- Advanced Electronic Monitoring
Gas Furnace Sizing
There are far too many factors for us to list on this page in reference to sizing a furnace for a home. Before a furnace is replaced, it is best to have a Manual J heating and cooling load calculation done on your home! This process takes into account hundreds of factors that will ultimately determine the right size equipment for you. From the number of windows and ceiling heights, all the way to the number of trees providing shade on your home during peak times of the day, everything is factored into the results.
The size of your gas furnace is actually a two factor calculation. You need the proper amount of heating BTU’s to keep the home warm in the cold months, but you also need to size the blower according to the amount of air conditioning you may need during the cooling season! The exact same home in Florida and Michigan, will use two completely different furnaces, so going by square footage is not an accurate measure as well. A home in Florida may only need 60k btu of heat, but 5-tons of cooling… whereas the same size home in Michigan would need 135k btu’s of heat, and only 3 tons of cooling!In many cases, when you are replacing a existing system, you are safe to replace it with the exact size you are removing. you should NEVER change to a larger size without first consulting an HVAC Contractor to make sure your duct and the rest of the HVAC system was designed to handle the size.
Here at webhvac we try to write reviews of the entire line of products by all the manufacturers. Please see the latest reviews we have completed below.
Latest Gas Furnace reviews in 2011:
- Bryant Preferred Series 123A Central Air Conditioner Review
- Dave Lennox Signature Collection XP25 Heat Pump Review
- Armstrong 4SCU13LB Central Air Conditioner Review
- Trane XB300 Air Conditioner Review
- Carrier Infinity 17 Model 24ANB7 Air Conditioner Review