The Effects of Draft on Your Burner

To operate as intended, oil burners need steady draft. In the heating industry, the term “draft” is used to describe a current of air in an enclosed space created by a pressure disparity. In other words, it’s a force that pulls or sucks exhaust gases out of the heating unit and into the chimney.


Draft variations can alter the amount of combustion air entering the burner, which affects how the burner operates. Low draft results in less air for combustion, and can cause smoke. High draft can cause too much air to enter the combustion zone, reducing system efficiency.


There are two types of draft: thermal and currential. Thermal draft is created when the air in the chimney is hotter, and thus less dense, than the outside air. Currential draft results from suction created by high winds or air currents passing across the top of a chimney.


Factors that can influence draft include:


  • The height of the chimney – the higher it is, the greater the draft
  • How hot the combustion products are – the hotter they get, the greater the draft
  • The outside air temperature – the colder it is, the greater the draft


In short, draft matters because it impacts the functionality of the oil burner. That’s why it’s important to regulate, and you can do so using a barometric draft regulator or damper. With newer heating appliances you won’t need to, as they’re designed to operate without one.


Older units are more susceptible to draft problems. Be sure to speak with your trusted Fsi Oil and Propane technician to have your heating equipment and draft regulating system evaluated.