# A/C Not Cooling the House Well



## fcabanski (May 3, 2012)

I have had two A/C companies check the system. They claim all is well.

Wednesday it was 86. I turned on the A/C for the first time this season at about 6PM. It ran constantly, and the temp was only down to 81 in the house by 10:30PM.

At 10:30 I set the thermostat to 80. The A/C runs about 30 minutes to get the temp down from 83 to 80. It then shuts off for about 10 minutes, the temp returns to 83, the A/C runs another 30 minutes.

I had the same problem last year and the A/C companies (two last year) said all was fine. They said don't expect the house below 80 when it's in the high 90's or over 100.

But it's only 75 outside now, and the A/C is running 50 minutes out of every hour to get the inside temp to 80.

Why have an A/C if it can never get the temp below 80?


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## beenthere (Oct 11, 2008)

Check to see if the indoor coil is dirty.


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## bill01 (Apr 12, 2012)

The house below 80 when its in the high 90's comment is related to how any AC works. They can only produce a certain difference in temperature. But this does not mean it can only produce 80 degree air. It means that it can drop the temperature say 15 degrees... so it depends what you start with.

If we assume the AC guys are correct and the unit is running correctly then I would be looking for ducting that is disconnected and dumping your cool air or taking in hot air. 

You can measure the temp difference yourself to see if the AC guys are correct. You should be able to use those instant read thermometers that they sell for kitchen use. You can generally find or make a tiny hole right before it enters the air handler and directly after it... of course you don't want to be anywhere near the moving parts. 

Last time I went searching for a vent issue I bought one of these. 
http://www.harborfreight.com/non-contact-laser-thermometer-96451.html

It let me see if cold air was coming out a register or not without getting a ladder.


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## av-geek (Jan 15, 2012)

A few things to check: Measure the air inlet temperature at the return, and the air outlet temperature at a supply closest to the air handler. There should be about a 15 degree difference or more between in and out (example, it's getting 80 degree air in the return and giving you 65 degree air at the supply vent). If there is, the AC unit is working properly. Also, you can check the refrigerant lines at the outdoor unit. The large line (low pressure gas) should be about as cool as a chilled drink, and if it's humid, it should be sweating. The small line, the high-pressure liquid line, should be about the same temp as the outside temp (IE 90 degrees outside air temp, and the line should be about 90 degrees).

If the large line is not cold, but only slightly cool, your system could be low on refrigerant. If it is frosty/icy, the evaporator coil inside your house could be dirty and not dissipating enough heat into the refrigerant. If the small, high pressure line is very warm, your condenser coil outside of the house could be clogged with debris.

What I think you may be dealing with is an issue of thermal mass. If this is a larger older home made out of brick and filled with a lot of "stuff", it is going to take a long time for the AC unit to cool all that mass down. Cooling the house down involves more than just simply cooling the air. You are also cooling all the materials and objects in the house, and these can hold much more heat energy than simply the air itself. You turned on the AC unit during the peak heat of the day when the house has absorbed the most heat energy from the outside. The AC unit is fighting a struggling battle trying to cool all the materials in the house...if it's cooler outside than it is inside with the AC running, You may be better off economically simply opening up all the windows and letting the cool outside air cool the house down, instead of the air conditioning system, then waiting until early in the morning before starting it back up. (after that, leave it on 24 / 7)

....either that, or get a larger air conditioner, but if you live in a humid climate, a larger air conditioner will not give you as good of performance in reducing humidity because it will run less once the house is cooled off.


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## fcabanski (May 3, 2012)

Another A/C company checked the system today. I asked the guy about all the suggestions here. He said they check all those things, and it's all fine. The A/C is the right size, there are no holes in the ducts...the system is fine.

He said when it's very hot outside the A/C won't cool below 80.

It's 87 outside, the A/C has been running non stop all day, and it's 84 in the house.

Surely an A/C can cool more than 3 degrees.


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## Marty S. (Oct 31, 2009)

Any chance of getting some info from one of those 5 service tickets? Return air dry bulb temp,return wet bulb temp, outdoor temp, air flow in cfm, model number, metering device, supply air dry bulb temp, supply air wet bulb temp. 

With that info we can tell you if the system is delivering its rated cooling capacity. Refrigerant pressures,superheat and subcool would be a nice bonus to help figure out what's wrong. Is there insulation in the attic and if so how much?


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## gregzoll (Dec 25, 2006)

If you leave the system off all day, then turn it on when you get home, yes it will take hours to cool the home. How much direct sunlight do you let into the Home? Are the windows & doors well sealed, is there is enough insulation in the attic, is it properly vented?

If it is 87 outside, and we do not have our A/C on, it could take up to four hours to cool down to 74, from being around 78. Then again, we have a two ton unit to cool a house that has total square footage of 1642, which is both the main floor and basement area, and have the unit on all the time, unless it is cool enough outside, that the house stays in the low 70's, high 60's. Normally our house gets no warmer than 73 before we get home and bump the thermostat down to around 71. We have no insulation in our walls, but the house is air tight, and has insulation up in the attic, and stays decent.

I would get the readings as stated in post #6 and post that info back, along with the info I asked about, including how big is the home, how old, are the windows also single pane or double pane, what is the model numbers of both the a/c & furnace, and the age of the units.


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## plummen (Jan 10, 2010)

Set the thermostat to a temp and leave it there,expecting an a/c to cool a 90 degree house off in an hour after all that dead air has been sitting for hours is the most rediculous(spell check :laughing complaint I still get from homeowners after all these years.
The first thing your system has to do when you fire it up is to start pulling all that dead air across your A-coil so it can start removing the humidity from the air before youll notice any kind of temp drop,this can a long time depending on how big your house is/location/size-location of returns/relative humidity...........
Once that takes place,then youll start to notice the temp drop.
If you want your house to be 70 degrees set it at 70 and leave it ,the a/c will work a lot less keeping a consistant temp then it will trying to make up from a 20 plus degree rise and a house full of dead humid air late in the afternoon.
If you do decide to raise the temp when youre not home,just raise it 5 degrees and leave the a/c turned on that way it doesnt have to work so hard.
Also close the curtains/blinds on whichever side the sun is shining on to keep heat out of house.
You can also keep a dehumidifier plugged in to pull misture out of the air ,which makes a major differance on how much a/c needs to run.


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## fcabanski (May 3, 2012)

"If you leave the system off all day, then turn it on when you get home, yes it will take hours to cool the home. How much direct sunlight do you let into the Home? Are the windows & doors well sealed, is there is enough insulation in the attic, is it properly vented?

If it is 87 outside, and we do not have our A/C on, it could take up to four hours to cool down to 74, from being around 78."

I turned the A/C on yesterday at 6PM. It ran constantly until 10:30PM and never cooled the house to less than 80.

After 10:30PM it cooled the house to 80, but no cooler. It ran at least until 4AM about 50 minutes every hour to keep the house at 80.

Thurs. it ran from about 9AM - 7PM non-stop. All the windows are closed, all the shades drawn. Two years ago it could cool the house to 75 and below. Last year, all summer, it was like this. The A/C people who checked it said that's the best it could do when it's high 90's.

It's not high 90's now. It was 87 Thursday, but the house was 83 all day. About 6PM it was 83 outside, the A/C was running non stop, and it was 84 inside the house.

I've called another company who set up an appointment for Tuesday. I will try to get the readings from them. If they claim nothing is wrong, I will post those readings.

Plummen: how long should it take to cool the house from 81 (that was the inside temp when I turned on the A/C Wednesday at about 6PM) to 78? After 4 1/2 hours the inside temp was still around 81, although it was less humid inside than outside.

I don't ask for much from the A/C. 78 is the lowest I set it.


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## Doc Holliday (Mar 12, 2011)

What's the supply air temperature and what's the return air temperature?


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## biggles (Jan 1, 2008)

we need to know the discharge air and return air at the air handler if you can cool at 75F outside air forget the higher temps with summer coming.how is the discharge air itself coming out of the register is it strong clean filter fan squirrels round clean coil clean...did they log freon pressures on the invoices?


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## plummen (Jan 10, 2010)

fcabanski said:


> "If you leave the system off all day, then turn it on when you get home, yes it will take hours to cool the home. How much direct sunlight do you let into the Home? Are the windows & doors well sealed, is there is enough insulation in the attic, is it properly vented?
> 
> If it is 87 outside, and we do not have our A/C on, it could take up to four hours to cool down to 74, from being around 78."
> 
> ...


 Send me a plane ticket,ive got a pretty flexable schedule these days! :laughing:
Can you post a picture of the inside/outside equipment and a picture of front of your house?


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## ben's plumbing (Oct 6, 2011)

just a thougth...before you start all kinds of checks....set your a/c to the temp you want and leave it there.....my guess your house is building humidity all day long..then you come home at 6 pm and start to cool...not good idea...so set it and forget it after a couple day you will know if its working:yes:


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## plummen (Jan 10, 2010)

ben's plumbing said:


> just a thougth...before you start all kinds of checks....set your a/c to the temp you want and leave it there.....my guess your house is building humidity all day long..then you come home at 6 pm and start to cool...not good idea...so set it and forget it after a couple day you will know if its working:yes:


 A man after my own heart! :laughing:


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## ben's plumbing (Oct 6, 2011)

plummen said:


> A man after my own heart! :laughing:


 looks like were on the same page on this one....:laughing:


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## plummen (Jan 10, 2010)

ben's plumbing said:


> looks like were on the same page on this one....:laughing:


 Youre gonna make somebody a fine Plumbing/Hvac guy! :laughing:


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## beenthere (Oct 11, 2008)

My A/C can keep my place at 72 when its 98 outside.


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## Marty S. (Oct 31, 2009)

Yep. Mine doesn't have any problem keeping the house 30 degrees cooler than outside when the hottest summer days come. Something is wrong if it runs most of the day and struggles to maintain 80 degrees inside on a 87 degree day. That's not normal.


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## clocert (Oct 14, 2010)

Call another A/C firm. there has to be a AC tech know what he is doing.


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