Yesterday's high was 106.0F, low of 79.2F, full sun all day. AC set at 78F, indoor temperature reached about 85F. Today's high was 105.4F, low of 81.1F, full sun all day, now about 102 at 7pm. AC set at 78F all day, temperature climbed steadily through the day, and is now 89F. Is it reasonable to expect an AC unit to maintain 78F in this weather? A properly functioning and properly sized central air conditioning unit should be able to maintain the temperature of your house at any reasonable temperature you select. The amount of cooling available is related to the size of the system, insulation in the house, and finally outside air temperature. From your description I would guess either you don't have a big enough compressor, or you don't have enough airflow through the house. It's also possible the cooling element in the system has become dirty and no longer transfers enough heat from the air into the element. The first thing to check is the return air filters.

If they're dirty, your system won't be able to keep up. Also, if the coils are dirty or the refrigerant is low, you will not get efficient cooling. You can clean your condenser coils (the outside unit) yourself using a jet of water from a hose. Contact a service company to clean your evaporator coils, do a system check, replace refrigerant and do repairs. The amount of in and out traffic you have, shade trees, insulation, type of windows, etc., all play a part in how well your system works. It's been about 100 degrees F here the last couple of days and the thermostat is set at 78 and has had no problem maintaining that. We had the same problem in our house, and we've simply lived with it - having had HVAC companies come out and inspect or evaluate it. They all said the system was in good working order, and was appropriately sized for our house. This year we replaced 3 windows and a doorwall in the first floor of the house, and suddenly we can not only maintain a temperature, but go lower if we want.

The air conditioning is doing fine, even though we've still got three old aluminum frame windows upstairs. replace a central air conditioning unitIt was about 80 square feet of window surface that was cheap double glazed aluminum frame, and is now cheap composite framed, double glazed with low-e coating. ac vs heat pump cost So if you've checked the interior coils, the exterior coils, and the system performance and it is still not cooling your house to your satisfaction, it is likely that you need a bigger air conditioner, or you need to better insulate your house - windows might be a big part of that loss.ac unit weather cover As others have said, if the unit is properly sized for the house, and the insulation is good enough to keep the heat out, and there is enough airflow in the house, the A/C should be able to handle almost any temperature you set it to.

There is a point where it gets so hot outside that air conditioners simply can't do anything to get rid of the heat (the outdoor coil temp equals the outdoor air temp). This is extreme though, >110 deg F. You're getting pretty hot, but shouldn't be at that point yet. (Most A/C units will have specs on this. You can try looking up some specs for it online.) You indicated the system is turning on and off, so I don't think it's your thermostat. How cold is the air coming out of your vents? If the system is working properly, it should be as cold as your fridge. If it isn't cold (not cool, cold), you have a problem. Look at the lines on the outdoor unit. Are they frosting up at all? Is there excessive dripping from your indoor air handler? If your lines are freezing up, turn the system off and call a service company. That means you are probably low on coolant, and running the system without will burn up the compressor. Other problems that would prevent cold air would be crud on the coil, or the fan on the outdoor unit not working properly.

If the airflow is weak, then you have an airflow problem. Check the air filters in the system. Make sure your ducts aren't plugged somehow. Check for closed dampers or closed vents. Make sure a duct didn't pop loose somewhere (blowing air into the attic instead of out the vents). Make sure your air handler is blowing air. To get a measure of your air condition performance , try to get a temperature reading, just in front of the inside unit. If it is below 10 Celsius - 50 Fahrenheit then it's probably working good and you have to consider the sizing issues of the unit (btu , size of room vs size of compressor etc). All this from my personal experience. Hope to offer some help. Top 14 Things You Should Know About Your Air Conditioning System two easiest and most important We accept cash, check, and all major credit cardsDEAR TIM: The air conditioning in my home has never seemed to work that well. My recent promotion and transfer have me moving into a new home that is in the very early stages of construction.

What can I do to ensure the new home has a central air conditioning system that keeps all rooms comfortable no matter the outdoor temperature? Is it possible to have all rooms nearly the same temperature, as my existing home's second floor feels like an oven? Julie F., Comstock Park, MI DEAR JULIE: Congratulations on your promotion! It is too bad you have been uncomfortable in your existing home for so long. I can think of many reasons why the central air conditioning in your existing home does not cool properly. Many of the problems might have been corrected with a simple service call from a professional who is an expert at air-conditioning troubleshooting. But it is entirely possible you have serious chronic air-conditioning system design flaws that would cost thousands of dollars to correct. The central air-conditioning system in a home, as well as the heating system, is one of the most important parts of a home outside of a sound roof and indoor plumbing. The heating and air conditioning systems create an artificial climate inside a home.

It is a very realistic expectation that this climate can be the same in each room. In my own home, each room, no matter the outdoor temperature or time of day (this is very important), can be within one or two degrees of any other room in my home. That keeps my family and me very comfortable. It is unrealistic for you to expect your home to be a certain temperature no matter what the outdoor temperature is. In other words, if the outdoor temperature rises to 115 F, I would not expect you to be able to cool your home to a chilly 72 F temperature without considerable discomfort on days when the temperature was say 85 F. Central air conditioning systems are designed to operate within a given range of temperatures. For example, the design temperatures in your part of the country may be only 20 degrees. This means that your air conditioner can only produce a 20-degree difference in temperature from the actual outdoor temperature to the lowest possible temperature the system can maintain indoors.

It is possible to create a wider temperature spread, but oversizing an air conditioning system can result in short cycling when the air conditioner has little work to do. If an oversized air-conditioning system short cycles or only has to drop the temperature a few degrees, it simply does not run long enough to remove humidity from the air. When this happens, the temperature inside your home gets to the desired level, but you feel cold and clammy. Properly designed central air-conditioning systems will run for ten or fifteen minutes at a time which allows them to extract humidity as the air flows across the cooling coils inside the air handler. The key to getting an air conditioning system to work properly is to have a real professional size the equipment properly and install a ducting system that delivers the right quantity of air to each room of the house. Each room must also have a return-air duct inlet that vacuums hot air from the ceiling and returns this air to the central system to be cooled once more.

A professional air conditioning person will take your new-home plans and analyze them using sophisticated computer software. This process will determine both the BTU (British Thermal Units) heat gain and heat loss for EACH room of your new home. This same exercise can be done on existing homes. With this data, the professional can ensure the proper sized equipment is purchased, and the ductwork that provides air to each room is sized correctly. This is of the utmost importance. Heat gain is the measurement of heat your house gains each hour during the summer months. This number can range from 20,000 in a smaller home to more than 90,000 in larger homes. There are many variables including but not limited to: amount of wall and ceiling insulation, number and size of windows facing west and south, amount of air infiltration, compass direction each wall of your home faces, number of people living in the home, etc. Heat loss is the amount of energy your home loses each hour when it is cold outside and you are trying to heat it.