I just moved into a house built in 2002 (just under 2400 sq ft, 1-story, vaulted ceilings on one side, one A/C unit) and noticed that the A/C unit is not keeping the house at the programmed temperature. We live in Florida so it is very hot right now but I've never had a problem with a relatively new A/C unit keeping the house cool before. On a good day the temperature in the coolest area of the house (where the control panel and intake vent are) is 3 or 4 degrees higher than the programmed temperature by mid afternoon. Today is a very hot day and it is now 7 degrees higher than the programmed temperature. The rooms on the side of the house with the vaulted ceilings (kitchen and family room) feel pretty warm by late afternoon. We've programmed the unit for 70 degrees around the clock so that it gets pretty cold at night when it finally gets back down to 70 degrees, but then at least it's not unbearable by late afternoon. Someone from the company that installed the unit in 2002 came out last week and said there wasn't a problem and that the unit is big enough for the house, but he did add about 1 pound of freon which hasn't helped. Does anyone have any ideas about what the problem might be? I'd like some information to be armed with before I contact the service company again. Your help would be greatly appreciated.

Could simply be the thermostat.

Thermostats are not perfect devices and can actually be off by many degrees.

If you notice your temperatures off by 5 degrees or so, simply set your thermostat setting lower by 5 degrees.

You could also check your ducts in the attic (if they run through it) to make sure they are insulated and that the attic itself has adequate insulation and ventilation.

If the attic does not have enough ventilation or insulation, it will keep your rooms below naturally hotter and therefore more difficult to cool and heat, and you will be losing more cooling to the attic because of lack of insulated ductwork and/or lack of vproper attic ventilation.

In my business (home inspection) we use a rule of thumb for A/C sizing. Start with about 700 finished square feet per ton of A/C. You might have to add some for high ceilings, southern exposure, alot of windows. It seems a 3 1/2 ton would be about the right size. Oversizing can be bad becuase the unit will short-cycle (cool quickly and not run enough to take out humidity). It should cool the air about 20 degrees. Also, check to see if a supply air register is blowing on the thermostat, that could satisfy the t-stat and shut off the A/C. If it runs all the time and the indoor temp does not drop, or rises, I bet it's undersized or inadequate insulation in the house.

I have a similar problem of all places in West Virginia. The vaulted ceiling areas need ceiling fans as a starter. I have some so my problem is not as extreme as yours. My biggest problem is in the largest area of vaulted ceiling there is no high level return duct. I think that when I fix that I will have a more even temperature. Assuming that you have adequate insulation, particularly in the vaulted ceiling, get a real accurate thermometer and check the readings at the thermostat and in each of your rooms. Here in WV we set a 24/7 at 78 and open the windows at night when the temperature drops to 76 or lower. If your HVAC system is reasonably hitech an increase of fan speed might also help. I also run my fan in the "on" position all the time vice the "auto" position.

Alot of our customers have this problem this time of year and they always forget to check their filter. Dirty filters will restrict the air flow. Your filter is located in the heater closet (if you have one) or in the return air grill in the ceiling. Good luck!

As one of the previous replies said, the air conditioning system should cool the air by at least 20 degrees. However, since in Florida the temperature has consistently been over 95 degrees you may simply be asking too much of your unit. I'd also try the idea of lowering the thermostat to 65 and seeing if it makes any difference. If the temp. doesn't go any lower than it has before then you know it isn't that the thermostat is inaccurate. Another way to determine this it to put an outside thermometer next to your thermostat and double check the actual temperature in that area.

I too am a home inspector but am also HVAC certified. First thing I noticed is the technician that came out said there was nothing wrong with the unit yet he had to put a whole pound of Freon in it. There had to be a leak somewhere in the system so that is a contridiction. A pound of Freon is a considerable amount. Typically if there is a small leak the system may only require a couple of ounces. This is a fairly common practice, of putting in more Freon when it isn't really needed. If he did an "overcharged" system will also do exactly what you are saying this one is doing. Chances are extremely good that what you have is Heat pump system. They typically perform very well particularly in Florida climate. You might want to consider getting another company to really check out the system rather than call back the same one. Hope this helps.

I do heating and AC here in NY it's my bussiness.
I would check the condencer outside the house to see it is clean of dust and dirt. Next this is the dirty job check the filter and the DX coil to make sure they are clean. The filter and DX if dirty can cause an air blockage. Put a ditital thermometer on the thermostat to make sure the temp. is right. These are good starting points. GOOD LUCK

First, find a new HVAC contractor. Builders usually go for the low bidder when it comes to heating and cooling. GENERALLY speaking, they lack training and expertise. Forget the yellow pages and ask around. Also,be patient. When you find the right contractor you may have to wait a day or to for him/her to get to you. Next, check your air filter. This is the answer to most cooling complaints. You can never change your air filter to often. DO NOT use the pleated white filters unless your unit is equipped with an oversize filter housing. These filters are very restrictive, reducing air flow...and have to be changed frequently! The filters work well....often to well.If you have to use them change the filter when it turns grey on the furnace side which won't take long. Third, the thermostat may be the problem. Make sure your outside unit cycles with a change in the indoor temperature setting. Fourth, check to make sure your insulation is adequate for your region and attic power vents are installed. Do you have kids? Are they leaving the doors open or windows cracked? If all these checks are satisfactory, in most cases your AC is undersized or has a mechanical problem such as a clogged dryer or bad compressor valves. A well trained technician will be able to identify and fix these type problems. If you must replace the outside unit and want to stay cool at any temperature, consider a two stage system that will carry the additional heat load in the hot summer months and run long enough to remove moisture from the air. Humidity control is very important.

I'm a heating & air conditioning contractor and I must agree with CB and a few other points made. Do check your air filters, big air flow restrictor. Next find a reputable contractor word of mouth usual get's a good one not the yellow pages. A good technician will be able to diagnoise the problem not tell you nothing is wrong, if nothing was wrong how come your thermostat is off? Something is wrong if only it is just the thermostat. As far as the size of the unit going by a rule of thumb doesn't work in most cases, the only true way is to have a load calculation done because there are far to many variables to consider. Good luck.

I am having a similar problem but only in one room of the house. I moved in about 5 months ago. The whole house was very cool I had to turn the heater on in March and part of April. Then I had this company to come in and clean my airducts and they also treated for mold. Now that room has been extremely hot. There is air cold air coming from the vent but there is no pressure or power behind it like the other rooms. I also notice that den the area right before the master bedroom is extremely cold. Would anyone know what the problem is or how to remedy this problem?

I just moved into a new home in Feb in the state of Texas. All my rooms were not being cooled and the living area and kitchen was Cold.When the sub concter who put it in came, some of the duct runs were to small and had kink's in them.
He strighten them out and added flow vents, my house now stay's even in temp, I hop this will help.

We had a similar prolem earlier this year - and it modified when we changed our filters. There are only two of us in our house, so no in and out traffic and the temperature was going from our daytime 72 to 78 or 79 during the day and dropping back down to our 69 at night. It was repaired within a degree or to by changing the filters. We sometimes get an inside high temp of 73 or 74 but it has not risen higher

I had the same problem one time. One of the return air ducts was disconnected where multiple returns connected to the plenum, and thus 120 degree attic air was being sucked into the system. This created a huge load for the AC to overcome. After reconnecting the return air duct, the AC worked perfectly. Be sure the HVAC companies check the entire system including ductwork, not just the compressor unit, coil, and filters.

Reading all the responses had me inspect my house. It looks like its a combination of many things. Our insulation is gone under the trailer. The full length of the house runs the south face. Our windows are not, well they are trailer windows from the 80's. And the thermostat is off. Taking all this into consideration, I'm moving into a house. Thanks for all of your replys.

Is it possible that someone at your house is always adjusting your programmable thermostat? I find that programming my thermostat and leaving it alone is the best way for me to be at a comfortable temperature. Even adjusting it up or down a few degrees seems to affect it.

If you've tried the other suggestions and it hasn't helped, try programming the thermostat to suit you, then leave it alone and see if it helps.

I am a homeowner with a year+ heat pump for heating and cooling.

Marilynne

Check to see if the damper [a flat piece of sheet metal inside the duct to that room, that will be accessible by a handle right near the main duct that feeds it] is open. The prior occupant may have wnated to close off that room for some reason. You will probably have to use a tool (wrench or screwdriver depending on the fitting) to loosen it before turning. NORMALLY the handle is in the direction of the damper, so that if the handle is parallel to the duct segment, it is open, perpendicualr, it is closed.

quote:

Originally posted by newhomeowner:
I am having a similar problem but only in one room of the house. I moved in about 5 months ago. The whole house was very cool I had to turn the heater on in March and part of April. Then I had this company to come in and clean my airducts and they also treated for mold. Now that room has been extremely hot. There is air cold air coming from the vent but there is no pressure or power behind it like the other rooms. I also notice that den the area right before the master bedroom is extremely cold. Would anyone know what the problem is or how to remedy this problem?

Hi! I own a house built in 1978, and the a/c is original. I check the filters monthly, and before I start the a/c at the beginning of the year; I shut off the power to it; and take the sides & top off the outside unit. I then clean it with the jet spray on my waterhose. If you have a friend who does a/c work they have a cleaning fluid they soap it with first; then just rinse it out. By doing this myself each year, it saves me about $100.00. Hope this helps you. T.

You do not need an expert to figure this one out. If you can not get up into your attic to see for yourself ( and I think everyone should be familiar with all of their home), then have a friend or pay someone to look and see if there is a kink, or a hole in the supply tube to your duct. The other option is that it may not be connected tightly to the vent. All easy stuff every home owner should be able to check out. Think of all the money you can save by being "house smart"?? Good luck.