Today I went to check what was makign an obnoxiously loud rattling noise coming from my central air unit's outside compressor. Upon silencing the loose, noisy gate that protects the fins by sticking a piece of wood in it, I noticed that the pipe that runs from the unit to the wall of my apartment was half exposed, half the insulation was gone.

I live in south Florida and it is very hot (in the 90s) now, and expected to get in the 100's by mid summer. Lately I have noticed that inside my house on the second floor, the indoor unit does not cool the house very fast. It takes about 2 hours for the thermostat to go from 78 to 77, and so on. Inside the rooms (our venting system is designed to cool the rooms more than the living room and hallway), it is cooler, but never gets really cool.

I was wondering if the exposed pipe outside was the reason why the air unit is not cooling the house quickly. Cold air (the thermometer measures 52 degrees F) is coming out of the vents at a good amount, but the house just doesn't seem to get cool. It's like there's a small heater running that slows the cooling down.

I did an experiment where I turned the tstat down to 74 whlie I was at school and when I came home 7 hours later it was at 75. The unit was still running, and I think it only got to 74 after 8 hours of running. Something tells me this is too long.

I will upload pictures for you to see.

The pipe
http://i3.tinypic.com/xonlgx.jpg

The HEIL compressor
http://i2.tinypic.com/xonkt0.jpg

I add that sometimes, the temperature will just go up. It's like it's not cooling the house when we are in it!

The exposed pipe on the outside of the house has no effect on the cooling of your house. The small line is the freon going into the coil inside and it should be very warm to the touch outside, the large line is the vapor returning to the compressor to be condenced again. The freon in this pipe has already done its job. The large pipe should be very cool, and on a humid day it should have some moisture on it. That is actually what the insulation is for is to keep the moisture from forming on the pipe and dripping on a space that could be damaged by moisture.

The cooling problem is something else, most likely the unit could be low on freon or the filter could be dirty or the evap coil could be dirty, several divverent things could cause it not to cool. One test that you can make to see if the unit is doing about what it is suppose to do. You will need a theomomoter that will read from about 40 degrees F to 8o degrees F. Now you will have to have access to the air entering the return air section of your furnace or air handler, Take the temp there. Then you need to check the register closest to the evap coil, or better would be in the plenum just about the coil, thake that temp. There should be about an 18 degree drop in the temp in the air coming out of the coil. A range of 16 to 20 is OK. This will give you a hint as to whether the unit is doing what it was meant to do.

Well, I think it hasn't been freon checked in a while. I will get it cleaned over the summer (but tell me if it needs it sooner).

The air coming into the handler is 76-78 and the air coming out of the vent is 52.

You missed the 18 to 20 degree total differention by 4 to 6 degrees. Your outside coil probably needs to be cleaned for proper heat transferr. Also have the service man check the pressures/superheat or subcooling while he is there.

Okay thanks. But I thought 76 - 52 = 24? Isn't that okay?

I'm a little confused. The return vent is the one on the inside air handler, and the evaporator coils are the thin medal fins behind the filter, right? The outside coils have probably never been cleaned, and the inside ones over 2 years ago.

Please tell me, based on what I know, where to measuere what. I am a noob here.

18 to 20 degrees is the usual standard for temp drop from return air to the discharge after the coil. When a pro does this he will also need to know the wet bulb temp at the intake of the return air. You are looking for a 18 to 20 degree total diferental.

Oh I see, you mean the air coming into the filter is the return air vent, and the air on the other side of the fins is what I need to measuere as the discharged air? How do you suppose I get behind the coils without taking the unit apart?

I do not know what you have? Upflow/downflow/horozontal/etc furnace or air handler. Let the pro show you when he arrives. He might have to put a hole in the area for taking the temp. You may also try to get the temp off the closest supply register but the temp there will not be as accurate.

Ill take pictures of the unit when I get home tomorrow so I can clear things up on what is what.

Thanks hvac1000, for taking over some times it is hard for me to get across what I am trying to tell someone on here. Normally you walk into a house and you do all the checks that you automaticaly do and it is hard to explain that to a person standing and watching you much less some one by typing messages to them, But one thing you should not say more about is the wet bulb issue or you will be here for a week... you gave good advice.

Here are more pictures that might help.

Air handler
http://i1.tinypic.com/zl92s4.jpg

Red T Coil label
http://i3.tinypic.com/zl94ps.jpg

Condenser coils
http://i3.tinypic.com/zl95r5.jpg

Buildup on the coils
http://i3.tinypic.com/zl9m5i.jpg

I think they are dirty... how should I clean them?

The coil need to be professionally cleaned. Have the HVAC service tech check your other items.

Sounds like you very likely have dirty filters--------these can keep the unit from cooling and are responsible for many unnecessary service calls---Rule of thumb---change your filters every time you receive an electric bill--you should have no problem with filters getting too dirty if you do this---best thing is to have an expert check system just to make sure all is ok--
After looking at the pictures your coil needs cleaning also---filters and a dirty coil can affect cooling tremendously

I replace the filter every month because it gets pretty dirty. That one is only 2 weeks old so it will be replaced at the start of next month. The camera makes it look dirtier than it really is.

I can conlude myself that the coils are really dirty. I will plan on getting them cleaned soon. Also, my outside unit probably needs cleaning.