FLAME Blog

Forced-Air Furnaces

Let’s face it, heating and cooling almost has its own language with all the babble about efficiency, stages, ducts (ducks?), SEER etc…  Sometimes it is just easier to smile and nod when somebody speaks of furnaces or air conditioners instead of trying to understand.  So the Flame blog is here to help you.  Here are some basic facts about forced-air furnaces.

 Forced-air systems can heat every room in your home from one central unit.  Because of this they are the most popular systems in North America.  There are three main categories of a forced air furnace.  These are:

Single Stage: As the name suggests, this furnace only has one “stage.”  It was basically designed and set up for one situation.  Whenever you have your furnace on, it will its use its full heating output.  It was set up to heat your home on the coldest day of the year, which means when it is not around 0 degrees, it is actually too big for your home. 

Two-Stage:  This furnace has two stages- low fire or high fire.  Low fire is when the furnace is operating at only 66% of its full heating capacity and it’s also only using 2/3 of the gas.  This furnace will only operate on high fire (or 100% capacity) when it is really really cold.

Two-Stage with Variable Speed Blower:  This furnace is basically the two-stage with the added bonus of a Direct Current Blower System.  This blower system will deliver great airflow to everywhere in your duct system.  Also, since it is direct current and not the usual alternating current electricity that can save up to 75-80% off of your electric bill!

On top of these 3 categories there are 2 other options for a forced-air furnace.  These are either Plus 80% efficiency or Plus 90% efficiency.  A furnace is either one or the other and it fits into the above categories.  For example-you could have a Plus 80% Single Stage furnace or a Plus 90% Two-Stage.

These percentages deal with efficiency and money.  Plus 80% means that for every dollar spent on gas, 80 cents go toward heating your home while 18-20 cents go out the window (literally). The 18-20 cents are vented outdoors.  With a Plus 90% furnace 90 cents of every dollar go toward heating your home while 5 to 10 cents of heat are vented outdoors.

There are other differences between Plus 80% and Plus 90% such as that Plus 90%’s are vented out through a PVC pipe on the side of the house whereas a Plus 80% is vented out through the chimney which means your chimney requires a liner.

As a re-cap:  you can get either a Single Stage, Two-Stage, or Two-Stage with Variable Speed Blower and all three of these categories come with the option of either a Plus 90% or Plus 80% furnace.

Forced Air Furnace

Though this information probably will not make you fluent in the language of HVAC (heating, ventilating and air conditioning), it should at least make you conversational.  As an added fun fact that you can impress people with-furnace comes from the Latin word, fornax meaning oven.

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