House too big for one A/C Unit?

Here's the deal


We live in Arizona, single story home aboout 2200 SQ foot(5 bedrooms, great room, family room, kitchen and 2 baths).


One A/C unit.





We moved in last summer before it got too hot. We found that the east side of the house is 8-10 degrees warmer than the west side. We had a A/C company come out to check it, running fine. No leaks or ventilation issues. We were told the builder should have put two units in for this size house.





1)Is this ture? Do we really need two units? WOuld one bigger one work better?





2)If we added a second unit about how much could we expect to spend





3)Are there any other alternatives we could try? We've already closed off hte vent in one spare room and keep that door shut, shut the vent in the master bath and master closet. Anything else?





Fortuantely the Master BR is cool, it's the other side of the house where th other bedrooms are that is HOT!! THanks!

House too big for one A/C Unit?
at 2200 sq ft depending on the heat cool analysis of your home your unit should be either a 4 or 5 ton unit depending on what the analysis tells the hvac tech you would need to cool your home on a 100 degree or hotter day...if it is smaller say 3 ton considering the area you live in and how well your home is insulated and whether you have double pane windows..that would be to small...you could possibly get by with just upgrading your unit and ductwork to a bigger unit....you shouldn't need two units...if you do add a second unit it will cost somewhere between 1500 to 2500 dollars per ton to install....install an attic fan that works with a thermostat that will keep the attic of your home cooler..this will allow your ac unit to keep your home cooler...
Reply:!.Some homes of that size do use two a/cs Example my in laws have a 4ton for the common ares LR, DR, kitchen, 1/2 bath, study and laundry... and a 3ton for the MBR, hallway 2BR and Full bath


2. A second unit add would be expensive, you're looking at a second breaker box, Additional ducting, new wiring..etc Between 6,000-9,000 min.


3. use your ceiling fans or install one. Another return in that part of the house. plant trees on the hot side of the house, Have a Heat load calculation done to see if a single larger unit would help (there is a charge due to the time that goes into it.)


Do not close any registers! You are reducing the air flow and compounding the problem.
Reply:Where is your unit located? Look to see how your duct work is running. The vents towards the end of the duct run will be receiving less air than those towards the begining (closest to unit). You said one side of your house is more comfortable then the other and i am thinking that is because it is closer to the unit. Check and see if your round pipes have dampers in them. if they do, I suggest adjusting your dampers towards the begining of you duct run to force more air towards the end.
Reply:call an HVAC contractor to size the house. I'm sure they will do this for free. many things factor into the size of an AC unit, such as windows, insulation, etc.
Reply:you cannot go by 2200 sf....they use a formula with takes into consideration the total volume of your home,ceiling heights are taken into consideration.also too geographic location.It get hot in AZ so you may need more tonage then someone in the north east.try going into your basement and or attic and adjusting the dampers .open them up (put the lever in the duct line in line with the duct where its warm in your house,and where its a little too cool close it down to 3/4).this will divert more air flow to the places where its needed.also too on the air handler there are usually high medium and low speeds.try going up one speed from what it is set at .that is if its not on high already.if this doent work you best solution is to get a bigger condensor.
Reply:Sounds like our FL house is similar to yours. We did/do all the same things! Being engineers, my hubby and I did a huge amount of research and calculations before buying a new a/c. So, I know that one unit is all that is needed for that size house. But we still have the same problems you do.





Last year, we added the newer tints on the south windows (hot side of our house) and wooden blinds (no holes) inside.





We found if we could keep the rooms from heating-up during 8am-11a, then the whole house stayed cool the rest of the day. Depending on the time of year, our hot-side switches from the south to the north....





There is also the chance that your attic is just too hot and radiating into the house. Or your clothes dryer could be sucking the cold air out of the house.





You don't need another a/c, just some investigating on the source of the problem.
Reply:Two units is the way to go - mostly because they will be run by two different thermostats in two different areas of the house. If you get a bigger unit, you will find that some areas of the house are going to get cooler than where your thermostat is located, and some will be hotter.





If you get the solar screens on the windows, it should help dramatically. Closing the vents near the thermostat will slow the cold air getting to the thermostat and keep the A/C running longer, which should help cool off those rooms.





Your A/C is probably working just fine, but you only have one thermostat, and when the temperature in the area that the thermostat reads in 'fine' (i.e. what it is set at), it will shut off regardless of what the temperature is in the rest of the house. (I shut down the vents to the nice and cool rooms which forces pressure to the warmer rooms, and reverse it for the heater in the winter).