Post above [ #26 ] does not seem consistent with 1st sentence in post #22.
Originally Posted by rk05
If the room temperature is better with the doors open the return is not optimum.
Some of your other observations hint at less than desired Supply Air.
Can your manometer measure 0.01".?
IF Not, you may not really know whether the areas are actually close to the same pressure.
Velocity pressure = 0.01" is created by 400 F.P.M. = (400/4005)^2
It's sounding like the Supply Air delivery is a problem.
Yes, the room temps get closer to the tstat temp when they are left open. The two outer bedrooms are still usually just a degree off from what the tstat reads when the doors are fully open but thats better than 5 degrees (during heating).
Mine is one of the liquid filled models, I'm not sure if it can go down that far but will look at it tomorrow.
My last contractor did a room by room manual J and D and from looking at it I have enough duct supply to all the bedrooms. I'm hopefully going to talk to him tomorrow and have him go over it with me.