Air Conditioning Question

[PCGumshoe]

I live in Florida, so it is very humid and between 80-94 degrees daily during the summer.

When I first moved into my home, I would set the AC to 72, then 74. I noticed it kept running and running never getting cool enough. I called my home warranty company and they sent out an A/C tech and he said it was all working fine and the size was appropriate for the house. He said it was less than 5 years old.

Now, I keep the A/C at 80 during the day and 78 when I sleep. I've installed a ceiling fan in the bedroom and I seem to be able to sleep better at this temperature. However, I notice now when it is 80 degrees outside (at night) and I have the temperature set at 80 or 78, it seems like the A/C is working all the time.

Is there something else I can do to improve the efficiency of my A/C? I seem to have to change the Air Filters (that claim to be 30-90 days) in less than 30 days.

I know I need to get rid of my windows and put in new ones, but I've tried to insulate my doors and windows better for now. but I can't understand the attempt to lower the temperature 1 to 3 degrees and it taking so long.

[sophiesdad]

When we first purchased our house we asked a similar question about the A/C - in our apartment, we usually ran the thermostat up to 80 and down to 74 when returning home (it was a very old apartment). Doing the same thing in the new house caused the A/C unit to run for almost

12 hours continuously to cool the space down. The A/C people told us that with the newer, high-efficiency units, they are designed to run longer and they are smaller in capacity than the old units. Their recommendation was to leave the thermostat set at a constant temperature and not monkey around with it. According to them, this is more efficient and keeps the energy bills to a minimum since high EER takes longer to take down temps rather than maintain a constant. Hope this is helpful.

JS

[Moe Jones]

You might want to spend the extra money and hire another A/C company to go out to your home and have them double check your system. Tell them you have had the system check and they found nothing wrong. This way the service tech. knows that someone has already checked the most common parts of the system. Heck it could be loose or disconnected duct work in the attic, your attic is not vented properly to relief the build up heat or could be a number of things.

To have them check your system should take a hour to two hours to complete an inspection.

Now one thing you can do is take the temperature at the return air opening, the filter grill, and then take the temperature at the closest supply air opening and see if the temperature difference is around 20 degrees.

[nicksanspam]

No. No. No.

Nick

[Jeff]

A home airconditioner should drop the air temperature about 20 degrees. Hold a thermometer in front of an air inlet and air outlet and check the temperature drop. If the temperature drop is significantly different then something is wrong. In a place like Florida with high humidity be carefully of dropping the temperature of your house below the outside dew point which often can be in the 70's. This can cause condensation in your walls which will encourage mold growth.

[udarrell]

In response to prior posts' a 2 or 3-Ton system is relatively the same BTUH rating & if installed properly "in dry climates'" should cool at approximately the same rate as the old condensing unit.

In high humidity climates the new higher EER & SEER condensers have a smaller BTUH compressor as compared to the two over sized coils. Therefore, they operate somewhat differently in high humidity climates where there is excessive moist air infiltration.

If there is high humidity content air infiltrating into our home the evaporator will use most of its capacity to condense that moisture from the air & very little to lower the sensible or actual temperature that you read on a thermometer or room TH!

First, go over your home with someone that knows how to seal it against excessive humidity infiltration into your home.

Next, go over every thing concerning the entire system that could be reducing the optimal transfer of latent heat (i.e., humidity condensation) plus total heat absorption & transfer to the condenser outside. Check the temp split of the condenser's discharge air against the outdoor temp & post it, that may provide us an indication of the amount of latent heat of condensation being removed, "or if there is an outside source Return Air leak." If the degree of Split is too low or too high, there could be a problem that needs correcting.

It could be overcharged or have numerous other problems needing attention.

Check out other of my pages so the tech will recognize that you have some knowledge of the system. Man, it should pull the temp down well below 78 at night & cycle off; IMO there are things with the home &/or the system that may need correcting. The indoor temp split varies with the % of Relative Humidity; buy a humidity gauge & tell us the readings.

- udarrell

[JimR]

[snip]>

[snip]

Also -- check your ductwork to see if there are air leaks into your attic or crawl space. These leaks will decrease the amount of cold air you get into your living area. It's not uncommon, especially with an older system, for leaks to have developed that will divert a significant amount of cold air.

[Edwin Pawlowski]

And your recommendation for efficiency is??????????????

[Stormin Mormon]

Sounds like your unit desperately needs service. There are several things that could cause this. A good AC service company can save you a pile of energy money.

[mm]

I don't want to be too cynical, but since this company would have to do the repair for free, iiuc, they have an incentive to lie. (Of course if they were going to charge, one could say they had an incentive to lie in the other direction. And at least once in a while, something works or doesn't work.)

Jeff said what I was going to say. Did the tech do this? Regardless, you should do it, so you'll know directly.

Is the fan on On, not Auto, and is it only the indoor fan running, or the outdoor compressor and fan too? Probably not, but you must eliminate this possibility, turn the fan to Auto, to go any further.

This sounds to me like nonsense. It may take an unappealingly long time to cool off your house when you come home, but if you put the house at 80 when you are not home, your AC won't run as much during that time, your house won't absorb as much heat during that time (because it will be closer to the outdoor temp) and you will save money. If you have a schedule, you can buy a setback thermostat that will turn your ac to the cooler temp before you get home so it will be waiting for you. But my AC can bring the house from 87 to 72 in about

4 hours iirc. Your 6 degrees is 40 percent of my 15 degrees.

[PCGumshoe]

I'm a bit confused...

I've taken temperatures at the two intakes: I have one that is 1'x2' and another that is 1'x1'

The intake temperatures were not far off... they registered 71.6 and

72.5. The temperature coming out of the A/C vent is 14 degrees.

Now, where I'm confused is that my wall mount controller reads higher than the room temps. In my office, the temperature reads about 80 degrees when I have my main PC on (It is a good heat source). I've gotten to the point of turning it off to keep from burning electricity AND heating up the house.

I think I need to check the digital temperature gauge that controls the system, and a few other recommendations here.

The only thermometer I had was a cooking thermometer. I also have a clock in the office that has a thermometer and that's how I gauge the room.

I'll review the above and report back more.

[mm]

Are you sure? 14 seems pretty low.

Is this like a thermostat?

:-) But I'm really not positive.

I think computers put out more heat than the lights do. I've only had the AC on for 4 days so far this summer, and I kept turning my pc off when I wasn't using it.

That's not going to be very accurate, I think. It's accuracy is centered around the temps of the food it is designed for, like melting candy or medium roasts.

When you live where it gets cold during the winter, you tend to have a thermometer outside so you can see if you have to put on warm clothes before you go out. When you don't, you just open the door to find out.

[Stormin Mormon]

With 14 degree air, you could almost keep ice cream in front of the vent. Good job! That's one seriously cold AC.