# mechanical draft appliance deffinition



## 907plumber (Mar 13, 2010)

What is the difference between a mechanical draft aplliance and a direct vent? Just that direct vent has a sealed intake pipe?


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## trick1 (Sep 18, 2008)

907plumber said:


> What is the difference between a mechanical draft aplliance and a direct vent? Just that direct vent has a sealed intake pipe?


Direct vent means that all air for combustion is taken from the outdoors and all flue gasses are conveyed to the outdoors.

Mechanical vent is simply "A venting system designed to remove flue or vent gasses by mechanical means, that consists of an induced-draft portion under non-positive static pressure or a forced draft portion under positive static pressure"

(From the International Mechanical Code)


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## 907plumber (Mar 13, 2010)

Lets take this a step further. WHat is non positive pressure and what is positive pressure?
Thanks!


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## OldSchool (Jan 30, 2010)

I am pretty sure it all relevant to the location of the venting motor. For either positive or negative Either it is at the equipment or it is at the termination



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