![]() ![]() This article and video are strictly for informational and demonstration purposes. This is a very serious issue and a furnace MUST be installed by a licensed HVAC technician. (This is not something to try at home, the furnace exhaust contains dangerous carbon monoxide. What do you think will happen? Check it out! The air infiltration can be minimized by reducing or eliminating openings and areas of possible air leaks and by controlling pressure in the furnace. This air has to be heated to the flue gas temperature before it leaves the furnace through the stack, which wastes energy and reduces efficiency. We’ve put a plastic flue pipe onto a gas furnace and run 500 degrees into it – simulating the heat of a low-efficiency furnace. Figure 1 shows rates of air infiltration resulting from furnace draft. A barometric draft control will help eliminate this undesirable stack action and permit the unit to be pressurized. So, understandably, these flue types are NOT interchangeable.Ĭheck out the video where we run a test to show you the importance of matching your furnace exhaust pipe to your furnace type. Forced Draft Burners Forced Draft installed with a stack height in excess of 30 feet will probably develop excessive natural draft, reducing the amount of pressure within the furnace or boiler. Plastic pipe is only rated to about 212 – 250 degrees Fahrenheit.Ī 92% or higher furnace produces condensation as a by-product and would rust the metal pipe, creating holes and then letting the exhaust. A metal flue pipe is built to withstand that level of heat and won’t melt, but the plastic PVC pipe is not. This is important because an 80% furnace will put out exhaust at about 500 degrees Fahrenheit through the flue pipe. While a draft hood (diverter) is often used on gas units fired with an atmospheric burner, a double- acting barometric draft control should be used for furnaces. Within 5 to 7 seconds in most cases and the rest of the furnace starts up from there. The inducer motor creates this draft quickly. ![]() If you have a 92% or higher efficiency furnace than you should have a plastic flue pipe. If the inducer turns on and is working normally, the furnace pressure switch should activate. If you have an 80% efficiency furnace, then you need a metal flue pipe. For more on this see our video: What is AFUE? CHIMNEY VENTING The flue pipe should be as short as possible with horizontal pipes sloping upward toward the chimney at a rate of one-quarter inch to the foot. (Furnace efficiency is also known as AFUE. Furnace rooms under 65m³ (700 ft³) should automatically be treated as confined space. Standard Efficiency furnaces produce heat at 80% efficiency while high efficiency gas furnaces produce heat at 92% - 96% efficiency. Furnace exhaust is dangerous and so having the right furnace exhaust pipe is important.ĭifferent types of furnaces require different types of flues. ![]() It’s good to have an understanding of what they are and why they’re important … and how they match to your furnace efficiency.Ī furnace flue pipe (also known as a vent pipe or simply as a flue), vents the exhaust from your furnace to the outside of your home. When the application calls for a long horizontal vent runs, undersized flue pipes, short chimneys, or an outside exposed chimney.Furnace flue pipes may not be something you’ve thought about before, but they’re an important part of your gas furnace system. After the burners ignite, the draft inducer continues to run in order to provide the burners with a constant source of oxygen. Those gases are pushed into the system flue pipes and vented out of the home. When the furnace begins a heating cycle, the draft inducer turns on up 30 to 60 seconds before the burners are lit and continues to run throughout each heating cycle.īecause it turns on before the furnace ignites its burners, the draft inducer is able to clear out any combustion gases that might be lingering in the heat exchanger from the previous heating cycle. How Does a Draft Inducer Work?Ī draft inducer is a fan that is located inside of the furnace near the heat exchanger. For venting single or multiple appliances, use a control kit. Draft Inducers are designed for easy installation in a wide variety of applications, including oil or gas-fired furnaces, water heaters, and boilers. What is a Draft Inducer?įield Draft Inducers solve the drafting problems caused by short chimneys, undersized vent pipes and negative building pressures. Use the Field Controls Contractors Reference Guide to choose the correct draft inducer for your application. DI Paks are available for 24 volt and millivolt applications and include all controls necessary. ![]() ![]()
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