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Jeni14 · Jul 22, 2010, 12:22 PM

I had my a/c unit replaced 2 months ago and it is running without stopping at all for over 8 hours. Yesterday it was 87 degrees outside, with a humidity of 63%. My house was set to 74 and the temp inside was 77. It ran all day and did not ever reach 74. I have had 3 companies, for a total of 9 times come to my house and they keep telling me it's normal for it to run for 8 hours. My house is 1200 square feet, a/c is 2.5 tons. 2 weeks ago they discovered the coil and the a/c unit were incompatible, and replaced that. 2 days ago they found a leak in the line, and repaired that, but it's still running non-stop and not reaching the temp of 74.

Last weekend the house was set on 74, but was 76 inside. I raised the temp setting to 76 to just get it to shut off. THe house temp rose to 78. I then raised the setting to 78 and the house rose to 80. And the a/c never stopped running the whole time.

Please help! I have never lived anywhere where the a/c didn't shut off the entire day... and I'm now being told that's normal. :(

hvac1000 · Jul 22, 2010, 03:04 PM

Originally Posted by Jeni14

I had my a/c unit replaced 2 months ago and it is running without stopping at all for over 8 hours. Yesterday it was 87 degrees outside, with a humidity of 63%. My house was set to 74 and the temp inside was 77. It ran all day and did not ever reach 74. I have had 3 companies, for a total of 9 times come to my house and they keep telling me it's normal for it to run for 8 hours. My house is 1200 square feet, a/c is 2.5 tons. 2 weeks ago they discovered the coil and the a/c unit were incompatible, and replaced that. 2 days ago they found a leak in the line, and repaired that, but it's still running non-stop and not reaching the temp of 74.

Last weekend the house was set on 74, but was 76 inside. I raised the temp setting to 76 to just get it to shut off. THe house temp rose to 78. I then raised the the setting to 78 and the house rose to 80. And the a/c never stopped running the whole time.

Please help! I have never lived anywhere where the a/c didn't shut off the entire day...and I'm now being told that's normal. :(

With the weather we have had around here this year so far mine runs almost 24 hours per day. That is because the unit was sized for 95 degrees outside temperature. A/C units are designed to run long times but I do understand your concern. Not knowing what the design temperature of your system is OR if they did a manual J on your home makes it just about impossible for me to help in your situation.

With 3 companys and 9 trips you would think they would have discovered all the problems by now. With a 87 degree outside and a 77 degree inside only makes it out to be 10 degrees split. I would figure your A/C system should do better than that but that would only be known if a manual J was performed. Sorry but that is all I have on this situation without further info.

Jeni14 · Jul 22, 2010, 03:11 PM

Originally Posted by hvac1000

With the weather we have had around here this year so far mine runs almost 24 hours per day. That is because the unit was sized for 95 degrees outside temperature. A/C units are designed to run long times but I do understand your concern. Not knowing what the design temperature of your system is OR if they did a manual J on your home makes it just about impossible for me to help in your situation.

With 3 companys and 9 trips you would think they would have discovered all the problems by now. With a 87 degree outside and a 77 degree inside only makes it out to be 10 degrees split. I would figure your A/C system should do better than that but that would only be known if a manual J was performed. Sorry but that is all I have on this situation without further info.

What does Manual J mean?

Also, just an FYI, the 7th visit the 3rd company found out that the coil was not compatible and it was replaced. The humidity inside the house was 86% at that point. After it was replaced it worked wonderfully for 5 days! It was 74 in there and I was freezing! Last night it got down to 73 and felt warmer than when it was 74. I'm thinking the humidity might be up again. I have someone coming tomorrow. I am going to ask them to check the intake temp, the vent temp, the humidity level. I may ask them what a Manual J is and if they can do that too.

hvac1000 · Jul 23, 2010, 03:06 AM

What does Manual J mean?

Manual J is a tool used in the HVAC industry to figure the proper size of equipment based on many different calculations. See Google for a more info.

KISS · Jul 23, 2010, 04:12 AM

This HVAC Software, HVAC-Calc for Heat Loss, Heat Load Calculations is essentially a software program that does a Manual J calculation.

Jeni14 · Aug 11, 2010, 06:44 AM

I am still having trouble. I had a technician come over about 2 weeks ago and said he could find nothing wrong with my system. However, I can't accept that nothing is wrong. I've never had an a/c unit operate like this and can give you at least 10 examples of people who's systems operate often, but do shut off during the day even when it's 100 degrees and maintain a certain temperature.

Here's what's happened:
Outside unit was replaced w 2.5 ton Fedders unit
Circuit breaker in circuit box was replaced with 240 volt breaker
Coil was replaced (about 6 weeks after outside unit was replaced)
A leak was found in the welding of the coil, and that was fixed.

I have been told to check my insulation in my attic, I have 6" of insulation up there.

If I set my house to 72 degrees, the house will maintain 75, if I set it to 77, the house could be as high as 81. This morning the outside temperature was 78, I had the a/c set on 75, it was running non-stop from 6:30am until I left at 7:45 and was maintaining 75. I will literally run from 6am until 1am without ever turning off and will be at least 2 to 3 degrees hotter in the house than what I have it set on.

Hopefully the company can run a Manual J today, I'm not sure if that's an additional fee or not.

I'm going to have them check the TXV valve. And I wonder if my 2.5 ton unit is just too small for my house which is 1200 square feet on the main level (basement & garage are below main level 1/2 underground). Any other suggestions?

ma0641 · Aug 11, 2010, 12:37 PM

6" of insulation is very inadequate either for cold or hot climates. You need at least an R-38 rating to get good temperature separation. 16" would be a great benefit winter and summer and pay for itself quickly, particularly with energy credits. I bet the ceiling is hot! Is there a powered attic vent fan or ridge vent? Your AC is trying very hard to cool the ceiling.

Jeni14 · Aug 11, 2010, 12:51 PM

Yes there is an attic fan... however I don't run it right now.

I will check the ceiling to see if it is hot. And look into more insulation.

Jeni14 · Aug 11, 2010, 01:12 PM

Would this be causing the problem that when my a/c is set to 72 the house is 75, but when it's set to 77, the house is 80? This is when the temp is 87-89 outside.

ma0641 · Aug 11, 2010, 02:38 PM

It's quite possible; if the differential is during the day and not at night it most certainly is. By attic fan are you talking about a central house fan or an attic ventilator? Where are you located? If you have a good handyman, blown in insulation is fairly easy and inexpensive. If you buy so many bags at HD or Lowe's, the machine is free. Dusty to do and best done early AM before it gets too hot.

Jeni14 · Aug 11, 2010, 02:43 PM

Yes this temp differential is during the day, usually around 2-7pm when the highest difference in set temp to house temp. I'm in Kansas City, Missouri.
I have an attic fan that you would turn on an open the windows... I'm not sure about an attic ventilator... my guess is no.

I'll look into putting more insulation in.

Thanks!

harlen · Jun 1, 2013, 02:18 PM

My ancient package unit would run a little while and shut off on hot days . Low electric bills. But got a cracked heat exchanger. Bought a new package unit same brand same size now ac never stops running and electric bill tripled temp in house always 3-4 degrees warmer than set temp . Called installer back 6 times .replaced thermastate 3 times , got lower efficiant filter . Called 2 other companies to check unit nothing wrong they say . My house has 2 units so I still have the twin to the old unit on the other side of the house runs a little and shuts off set it to lowest setting that side of the house got so cold I had to turn it off . My vents are ice cold on the new machines side but air flow is low the room farthest from the unit needs a heater in the winter. Now . And is hot in the summer . All I can think is the airflow output is too low the blower has burned out twice so far it has a high or low wiring and is wired for high so the repairman say . Can the blower motor be replaced with a higher air output? Blower motor goodman brand?? Maybe this is our answer?