Furnaces and their differences
Furnaces come in many shapes, sizes and brands. They also have different materials used to exhaust gases out of the home. Traditional, or conventional low to mid efficiency furnaces produce hot exhaust gases, and need metal vent pipes or chimneys to let these hot gases out. Modern, high efficiency furnaces produce much cooler temperature gases and can use plastic pipe materials such as PVC or ABS for the exhaust vents. Typically there will be a second plastic pipe as well that brings in fresh air.
These high efficiency furnaces have a 2 stage combustion in order to extract as much heat as possible, and this process results in condensate ( moisture ) from the heat exchanger. This condensate drains through a pipe down into the floor drain. It is typically a 1 inch wide rubber or plastic hose.
Types of Furnace Venting Systems
There are 2 types of furnace venting systems, 2 pipe or direct vent systems, and single pipe which have non direct venting.
Direct vent (2 pipe)
This 2 pipe system is typically the most common in today’s homes. They have a direct vent bringing air in from outside, and a direct vent to release all the gas outside as well. With this system you can see 2 pipes sticking out of your home.
Single Pipe (non-direct vent)
The single pipe, non direct vent system ( also called atmospheric) is used when there is no need for a separate air intake vent. These have a metal vent pipe for getting rid of the gasses, but they depend on air around the furnace for the combustion air. These vents are always connected to a brick or stainless steel chimney that comes out of the roof.
As a Home Inspector, I never know what I will find when doing an inspection of the HVAC system, I have definitely seen some different setups, but the two above mentioned types are the most common out there, and if you’ve taken the time to read this, I hope it has answered any questions you may have wondered about.
Lastly, it’s a very good idea to have a qualified HVAC technician clean and inspect whatever system you have annually, in order to keep your home safe and running efficiently.
Stay warm ! Winter is coming !!
Pegasus Home Inspections LTD.