So my house has three zones.

First floor

second floor

master bedroom

I also have several returns throughout the house I believe on the first floor I have two floor mounted ones.

And on the second floor I have four or five I think.

Master bedroom has one.

But I'm curious about is when master bedroom is on there is a huge pressure differential from the door and it feels to me like it's pulling return air from all of the returns in the house rather than the return in the master bedroom and I'm not sure if that is correct or not.

Pressure differential is so great that it will end up slamming the master bedroom door quite hard when it kicks on which as you can imagine is not really exciting in the middle of the night

I noticed that most in the master bedroom just because the master bedroom has a lot of supplies and only one return.

But this also happens with all other zone in that every zone supply get this air from every return.