Zone damper system
A bypass damper bypasses air from the plenum comming out of your unit going back into the return air system or dumped off in an uncontroled area. Its usally a manual damper with a weight on for adjustment, that when the majority of the zones start closeing off the pressure builds up in the ducts so it releves the pressure.
Think of it this way. Your blower it pushing enough air to feed the whole house, then you change the zone so only one room or one zone (smaller then the whole house) is calling for air, all the dampners close except one zone which is alot smaller the air in the system builds up and slowes down so a bypass damper (with a wieght on it) starts to open to release the air either back into the return air plentum or return air line going to the plentum or something along those lines (can be dumped in a hallway or closet too), that way the air just makes a loop and passes back threw the unit again.
Last edited by integlikewhoa; 12-24-2008 at 01:30 AM.