I have a customer that calls me every season to service the unit (5 ton common central unit)
The unit is doing a good job but the metal duct is 11" wide by 4" deep and to me I think thats to small.
She has no air upstairs to speak of and Shes blocking off all the vents to try to force more air up stares.
I checked all the duct work and everything is all metal and just about no leaks to be concerned about but I did tape the seams anyway.
The biggest problem is She doesn't want a fan installed because the noise travels into the room and keeps her awake.'
Last year She paid me to install a fan in the duct and I also installed a sail switch but to much noise for her.
So now i'm thinking of installing a fan over the vent and have it PULL air rather then have a fan in the duct force air.
Also the vent closest to the unit does not impressed me with the flow so at this time I like to increase the efficiency and then see what happens.
Home is a large split level with 3 rooms above and the main bed room above the garage.
Right now i'm lost on this one.