Duct from supply to return

Specific Inspection Topics Inspecting HVAC Systems
1

Hey guys I was looking at the 90 day warranty video from Nathan. The furnace has this duct that goes from supply to the return. Why is that there?

2

Barometric bypass damper for zoned systems.

3

Thanks David. At least I have something to google now

4

It will have a barometric bypass damper which needs to be properly oriented and adjusted too.

6

I’ve never seen it before. Thanks for the video