Is it Time For a New Furnace?

is-it-time-for-a-new-furnaceWhen it comes time to replace that old furnace, you may have tons of questions and probably a few concerns. You can speak to as many contractors as you wish and get as much advice as possible, the choice to replace it will ultimately be yours to make. Knowing the key things that go into you making an informed choice is most important. Most people don’t know much more about their furnace other than how to turn it on and/or where the filter is located. Below are answers to key questions that should be answered prior to replacement.


Key Terms

Ductwork/Ducts –
A system of tubes in rectangular and circular shapes that carry heated or cooled air throughout your home. Supply ducts move the heated or cooled air into the room, while return ducts help the internal air from rooms return to the furnace.

Heat Exchanger – This is a device in your furnace that keeps the exhaust from the fire in the furnace separate from the air that blows it out of the supply ducts and into the rooms of your home. The flames heat the inside of the heat exchanger, and the exhaust flows through it directly to the exterior of your home through the exhaust vent. The air coming into the furnace from the return duct then passes over the outside of the hot heat exchanger; heating the air which then blows out of the supply ducts into the rooms of your home

Blower – This is a fan that moves the air through the furnace. It sucks air into the furnace through the return ducts and blows it out of the furnace into the supply ducts.

Inducer/Draft Inducer fan – The fan that moves the combustion products (exhaust) through a mid or high efficiency furnace and out through the exhaust vent. Standard efficiency furnaces do not have this feature.

Thermostat – A device that senses the temperature of the room and uses the information to turn the furnace off or on as needed.

How does a furnace work?
A forced air furnace burns fuel and distributes warm air throughout your home. Gas is burned below the heat exchanger. The heat that has been produced flows up through the heat exchanger and then out through the exhaust vent. Depending on your furnace, the exhaust vent maybe be a metal vent that goes into a chimney or through the roof, or it may be a plastic vent that exhausts directly to the exterior of your house.Anytime the thermostat senses that the temperature is too low in the home it sends a signal that turns on the furnace. Combustion occurs and warms the heat exchanger. After a short period of time the blower turns on and circulates the heated air.

The furnace circulates the warm air through your home using the supply ducts, and the cool air is sucked in through the return ducts and goes back to the furnace to be heated again.

Types of Forced Air Furnaces

Standard Efficiency Furnace – A furnace that has an efficiency of about 60%. These types of furnaces are used to heat homes built in 1970 or earlier. They must be vented using either a masonry or metal chimney. It uses a simple system with no draft inducer fan, but it wastes energy and heat.

Mid-Efficiency Furnace – A furnace that has an efficiency of about 80%. It has a better heat exchanger that utilizes more of the heat created from the combustion to heat your home. Condensation is mostly prevented inside the furnace but is possible in the chimney. This condensation is acidic and puts wear on chimneys.

High-Efficiency Furnace – A furnace that has an efficiency of about 90%. It uses a second heat exchanger to remove even more of the heat from the exhaust before venting, making it even more efficient. Because the exhaust is cooler, the furnace can be vented with a plastic pipe instead of metal. There are also furnaces that can go beyond the 90% efficiency.


Which Efficiency Should I Choose?
When deciding between a mid or high efficiency furnace, there are several things that should be considered beyond just cost and energy savings.

Water heaters, like furnaces, can have different types of exhaust vent pipes or none at all. Electric water heaters do not have exhaust since there is no flame inside heating the water. Direct vent water heaters use a fan to blow the exhaust outside through a plastic pipe. Most water heaters use a metal exhaust vent which they often share a chimney from a standard or mid efficiency furnace.

If you update to a high efficiency furnace that doesn’t use the chimney, the chimney flue is too large for just the water heater. This can result in damage to the chimney and exhaust back drafting into the house. A metal chimney liner must be installed to prevent this. As a result, many times the cost of either installing a chimney liner or updating the water heater must be considered as part of the process of picking a furnace.

One of the potential benefits of installing a high efficiency furnace and either electric or direct vent water heater is that a chimney is no longer needed and can be removed. The space can then be opened up or used to add extra storage shelving. Another great use in older homes with two stories or finished attics is to run additional return ductwork up through the space where the chimney was since often these areas weren’t built with sufficient, if any, return ducts to allow a central air conditioner to cool the air.

Does the Size Matter?
The “size” of a furnace is based upon the input BTU per hour. A residential furnace can be as small as 40,000 BTU or larger than 200,000 BTU. Furnaces installed more than 20 years ago are often oversized and can be switched out for a smaller one. Your contractor will help choose the correct size of your furnace size by performing a heat loss calculation and taking into account other factors (e.g. square footage, home type, number of stories, number of windows, insulation, orientation and sun exposure.)

Do I Need a Contractor?
Furnaces and air conditioners should be maintained every year by a qualified contractor. It is vital that you find contractor that you are able to trust. He or she is responsible for helping you choose the right type of furnace as well as maintaining it. When asking others for a reputable contractor be sure to check their online ratings and customer references. A good contractor is the key to a safe and comfortable home.

Do you have a question regarding your existing or future home?
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