First Furnace Install - Need Some Help Getting Started
A plenum is usualy the first piece of metal on the outlet of the furnace, the trunkline is any ductwork that follows.
If you are using a horizontal built up air handler, you may not need a plenum, the main trunk screws directly on the air handler discharge opening.
Establishing a consistent pressure and smooth, uniform flow is what needs to be focused on, plenums are sized for and used to establish both, so that distribution of the air can be predictable.
Last edited by 8 Ball; 10-05-2008 at 10:57 AM.