Gas and Oil Home Heating Furnaces - proper size for AC

We recently bought an older home which was renovated and has had the garage closed in. There is approx. 1700 sq ft of heated living space. The house has (2) 2 ton each ac units. One in the hallway closet to cool the bedrooms and living room. The other is at the oposite end of the house cooling the garage/bedroom and kitchen areas. Both of these never seem to turn off. The house is always hot. An energy survey by our power company will upgrade the attic insulation. I would like to run new ductwork from the garage side unit which has it's air handler in the attic, near center of the house, to create new runs feeding the rest of the house. Is this a good idea? Is a 2 ton unit enough?? How much distance from the handler box to each drop? Then I'll just centrally relocate the thermostat and hopefully have a much more comfortable home!

Read the current post "York "a" coils " and check it out.

I doubt that the units are too small. Another possibility is major duct leakage which imposes an unseen load on the equipment that us pure WASTE.

Thx for the info about the A coil. After finding the filter to be beyond belief I spent some time cleaning the unit and replacing w/ a new filter. Helped a little. The big problem is that the house had an addition done wherein they added a trussed roof over a flat gravel roof. In order to AC the added on master BR and bath they dropped the ceiling running a single section of rigid duct work within the dropped ceiling. This one leg has 3 registers directly cut into the duct, thus feeding three rooms in line as you walk down the hall. No wonder the last room, the master BR doesn't get any air! That's also where my wife has her office space, let's just that momma's not happy.
Here's my idea.. the house has 2 - 2 ton units which attempt to cool this place- about 1700 sq ft living. One at each end. The second was added to cool a garage which was finished out to a bedroom. I can access the air handler in the hallway via an area where the old roof has been cut away. I'd like to close off the dropped trunk and bring the main feed up into the attic then run individual ductwork to feed the master BR and bath area as well as feed the garage and kitchen thus having one unit cool the whole house. Again a total of about 1700 sq ft. Will the one unit be enough for that amount of living space? My plan is to extend the rigid feed from the top of the air handler up into the attic area then use flexible duct work. The longest run will be to get to the garage area-about 50'. Is there a better way to do this? I just shudder every time I hear 2 AC units running. Thanks. Regarding cleaning the indoor coils, I want to clarify, are you supposed to pull out this coil unit to clean it or not? Simple green ok? Lastly the return for this air handler pulls from the bottom of the unit, which is in a hall closet so it's pretty much open at the bottom. Any way to improve the flow to the return? The closet door is vented. Whew!

Go to the website http://mrhvac.com/
Look for the calculator section and the "Manual J heat load".
Use this tool to see if 1 unit will do the whole house.

The next issue is getting the correct amount of air into every room. This is no easy thing to do even when the house is under construction. The design is not easy. The contractor who installed your present systems failed to make it work with 2 units.

You need a room-by-room heat calculation to allot the air to each room. Then you must design the duct system to do that. The twists and turns of the airstream make the design complicated. I'd say that you need a pro to go on from there.
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Cleaning the indoor coil...did you read the thread that I sent to you? The dirt collects on the side of the coil where the air enters the coil. Sometimes the lineset may allow you to slide it out some. Otherwise you have to remove the triangular side plate to expose the dirty coil-face. Good Luck.