Return Air at top of 15 ft vaulted ceiling ok? (how much, AC, heater)

[5x10]

I just added a 2nd unit to my 3000sq ft house
I had a 5 ton, but it wasnt cooling one side of the house very well(even after adding an additional duck to cool that side of the house)
Now, the once warm side is now the cool side(its cooled by a 2 ton unit)

When I leave the cool side, I walk into my living room(25x17, 15 ft vaulted ceilings,cooled by 5 ton) and I can feel a substaintial temp difference(warmer).

It is a good idea to move our largest return air(for the 5 ton) out of the back hallway and up to the top of our 15 ft ceilings in the living room, with the intention of pulling the hot air out and cooling it?
Any cons to this?
Or would it be a better idea to add another duct and a couple of more outlets to this room(only 2 currently)
Or both?
Im not worried about losing warm air as I am located in TX and rarely use my heater

All advice is appreciated

[CptnRn]

It would be better to draw the return air in near the level that you are trying to cool, and for the thermostat to be located near there also. Otherwise you will be returning the hottest air in the house to the AC unit and trying to cool it down to your comfort level. Hot air is always going to rise and stratify, so the air near the ceiling will be hotter then the area you occupy, that is OK who cares what temperature it is up there, as long as you are comfortable down closer to the floor.

Its not clear from your post how the return and supply air ducts are laid out, it would be desirable to keep the two systems isolated as much as possible. Two supply registers sounds a little low depending on how much air is being delivered to each one.

Any competent HVAC contractor should be able to help you adjust with the design and correct installation of the two systems you have in your house, but since this does not appear to have been done properly previously, perhaps you should hire an Mechanical Engineer to help you evaluate your systems and layout.

[BigJon3475]

Can you describe your house more? Size? Size of returns? basic setup? If you have pictures that would be wonderful. And you have 7 tons of cooling capacity?

[5x10]

Originally Posted by CptnRn

It would be better to draw the return air in near the level that you are trying to cool, and for the thermostat to be located near there also. Otherwise you will be returning the hottest air in the house to the AC unit and trying to cool it down to your comfort level. Hot air is always going to rise and stratify, so the air near the ceiling will be hotter then the area you occupy, that is OK who cares what temperature it is up there, as long as you are comfortable down closer to the floor.

Its not clear from your post how the return and supply air ducts are laid out, it would be desirable to keep the two systems isolated as much as possible. Two supply registers sounds a little low depending on how much air is being delivered to each one.

Any competent HVAC contractor should be able to help you adjust with the design and correct installation of the two systems you have in your house, but since this does not appear to have been done properly previously, perhaps you should hire an Mechanical Engineer to help you evaluate your systems and layout.

i hear what your saying, but doesnt the hot air at the top get pushed down when i turn my fan on?

Originally Posted by BigJon3475

Can you describe your house more? Size? Size of returns? basic setup? If you have pictures that would be wonderful. And you have 7 tons of cooling capacity?

aprox 2800 sq ft house, all have at least 12 ft ceilings
5 ton on the north side of house, cools aprox 2000 sq ft, has 2 return airs now, one 20x25 with a 14' duct(in the hall next to master), one 16x20(in the kitchen, near the top of the vaulted ceiling)

yes, combined 7 tons of cooling capacity

the living room(the hottest room) is the furthest from the 5 ton, the 3 rooms that branch on the south side of the house is cooled by the 2 ton

Im thinking of adding a duct from the 2 ton or the 5 ton into the living room since its so large
not sure which ac to do it from

when they added the 2 ton, they took away 2 12' ducts from the cool air outflow unit of the 5 ton

might just need another duct from the 5 ton

thanks!

[BigJon3475]

and what kind of filters do you use? Those returns for the 5 ton unit are a little on the small side. If you're using more restrictive "effcient" filters it will compound the problem. If you have flex duct it may also be compounding the problem. What is the duct work flex or rigid?

[5x10]

Originally Posted by BigJon3475

and what kind of filters do you use? Those returns for the 5 ton unit are a little on the small side. If you're using more restrictive "effcient" filters it will compound the problem. If you have flex duct it may also be compounding the problem. What is the duct work flex or rigid?

flex ducts, looks like foil on the outside of them

theres one main large filter thats attached on the unit itself
no filters on the return air grates themselves