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Old 08-14-2007, 10:44 PM   #1
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New A/C unit won't cool in hot temps


I have the same type of problem with my A/C unit as a previous posting. I bought a brand new 13 Seer Trane unit for my 1500 sq. foot home about a year and a half ago. The system that I had before was an older 15 year, 10 seer York unit. The York cooled awesome even in 100 degree temps. It had freon leak problems all of the time, and then eventually it couldn't live on anymore. The new Trane unit was installed in March, and seemed to be cooling fine. As soon as June and the hotter months came, I would notice that the temperature would go up a few degrees than the temp. that I had it set at. For example: I had it set at 77 and then during the mid day it would go up to 78, 79, 80 and would stay at that temp, until the temps outside cooled down a little bit. I called the company that installed it, and they came out to check it. Ofcourse, that day was a little cooler, and the system appeared to be cooling properly. This would happen again and again throughout the entire summer, and the company would say nothing is wrong. I finally decided to give up, until this summer, when it happened again, but worse. I live in florida and it got to 85 degrees in my house!!! I decided to call another company since I am no longer under warranty for labor with the company who installed it. They came out and checked everything, the pressure, air handler, freon, leaks, compressor, thermostat, filter, and said that they couldn't find anything wrong either. They did notice that there were a couple of small leaks in the ducts, but told me that shouldn't make the temps that much warmer. The A/C did stay at the temp that I set it at too that morning, but right after he left, the temp went up 2 degrees higher. I called him back and told him to look again. He still couldn't find anything, but suggested it could be that the ducts are too small for the new system. I was desperate and said, lets do it. Today they just installed a 18" duct at the air handler and supply unit, and fixed the leaks in the ducts. Cost me $425, guess what? It still doesn't work right! It was at 80 degrees all night at my house. They are coming back out tomorrow, does anyone think it could be electrical?

Thanks!

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Old 08-16-2007, 04:56 PM   #2
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New A/C unit won't cool in hot temps


And they say its hard to stop a Trane...............


Need to check the sub cooling value as well as the delta T when the unit is acting up.

Also what are the pressures running at? Is the unit removing condensate?

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Old 08-16-2007, 05:46 PM   #3
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New A/C unit won't cool in hot temps


I can't see how anything electrical would be a problem for you. As harley said the performance needs to be checked. Maybe they don't have enough airflow through the system.
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Old 08-18-2007, 09:39 PM   #4
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New A/C unit won't cool in hot temps


Are _all_ the supply ducts insulated for their entire lengths from the furnace/blower to the supply vents in your rooms?

Can you get into the attic and see if there is a disconnect in some duct joint?

Think back to the installation of your new AC. Where did the contractor go? What did he do or change?

Could there be a damper in some duct that is cross-wise and blocking the flow?

Turn the fan to on (constant) and put your hand next to every supply vent in every room to see that there is flow to that vent.

Borrow a temperature sensor, or get an HVAC guy out there who has one, many of them commonly carry one, and point it at every supply vent when the AC is running to read the temperature coming out of that vent. They look kind of like a water pistol, roughly, and use a laser or IR beam to sense the temperature.
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Old 08-20-2007, 02:03 PM   #5
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New A/C unit won't cool in hot temps


Does the A/C shut off when the inside temp is above your thermostat setpoint or does it just keep pumping?

Is your new A/C the same size as your old one?
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Old 08-20-2007, 07:26 PM   #6
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New A/C unit won't cool in hot temps


My problem is simular to yours and I noticed that mine was not cooling like it used to; so I called the installer. Before he arrived, I determined that the 2 speed compressor was staying in low cool mode and would not go into high cool even when we had temperatures over 95 degrees with high humidity.
Now according to the manufacturers brochure, my unit which is a puron unit by "Bryant" runs in low cool 80% of the time and when temperatures demand it, it will run in high cool. The manufacturer does not state under what temperature will this unit go into high cool. So the installer did call the mfg. technical support and ask why my unit was hung up in low cool.
They stated that these new units can develop a history which is constantly read and it adjusts the history along with any settings you make.

So it appears to me that all this does is confuse the control boards as to what the homeowner desires in comfort if I were to believe the factory. This is certainly not a home owner issue but a factory glitch that they do not want to get involved with. The components all checked out ok.

So I thank the serviceman and told him I would give it some more time to see if it will perform like I think it should. I also believe that there is a miscommunication between technical support and the serviceman and I intend to call the manufacturer and ask for techical help direct.

BUT HERE IS A TIP THAT WORKS FOR ME:

Take a thermometer and read the output temperature of the closest discharge at the normal setting of your thermostat after the compressor has been running for 10 minutes. Now lower the thermostat 5 degrees below the normal setting. Wait about 10 minutes and take another reading. If you get a much cooler temperature, then this will take out excessive humidity and start to lower your house temperature. Now what you just did is called "forcing it into high cool". I am assuming your system works simular to mine.

Now once the humidity is removed to a comfort level, you will have to adjust the thermostat back to your desired setting or you will freeze yourself out. Now doing this will temporary give you some comfort because the next time there is a demand for cooling, I believe your system will start in low cool and not go back into high cool (when the demand is there) and you will have to force it into high cool again.

I know this is not a satisfactory solution but it is only meant to give you some comfort until you get the factory to cooperate more with the service technician.
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Old 08-20-2007, 07:45 PM   #7
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New A/C unit won't cool in hot temps


As a addedum, I would contact "Trane" factory direct and ask them for the best troubleshooter in your area and explain to them that your original installers cannot determine where the fault lies in your system. And never let anyone guess what they think is wrong. They are supposed to be professionals and know all about duct sizing. Do you still have the factory brochure describing how the compressor performs? See if it says 2 speed.
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Old 08-21-2007, 12:24 PM   #8
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New A/C unit won't cool in hot temps


I don't mean to point out the obvious, but did you check your filter and condensing unit heat exchanger, i.e. the fins? I had a friend who had a similar issue and I agreed to look at it. First I found a waaay dirty filter and replaced that which created some immediate improvement. Then I checked the condensing unit and noted that it had copious amounts of dirt in it. I cleaned the exchanger with my air compressor and then the system was blowing ice-cold air.

Just a simpleton thought!
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Old 08-21-2007, 12:25 PM   #9
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New A/C unit won't cool in hot temps


rjordan's information is very interesting and his suggestions are excellent, but be certain that you answer the questions that I and jogr gave you _before_ someone comes out. Not only might that tell you what the problem is, but even if it doesn't solve the problem, it should allow you to determine the skill level of the person who comes out by how he responds when you tell him what you have done and what you have tried.
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Old 06-26-2012, 06:30 PM   #10
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New A/C unit won't cool in hot temps


Quote:
Originally Posted by wishiknewmore View Post
I have the same type of problem with my A/C unit as a previous posting. I bought a brand new 13 Seer Trane unit for my 1500 sq. foot home about a year and a half ago. The system that I had before was an older 15 year, 10 seer York unit. The York cooled awesome even in 100 degree temps. It had freon leak problems all of the time, and then eventually it couldn't live on anymore. The new Trane unit was installed in March, and seemed to be cooling fine. As soon as June and the hotter months came, I would notice that the temperature would go up a few degrees than the temp. that I had it set at. For example: I had it set at 77 and then during the mid day it would go up to 78, 79, 80 and would stay at that temp, until the temps outside cooled down a little bit. I called the company that installed it, and they came out to check it. Ofcourse, that day was a little cooler, and the system appeared to be cooling properly. This would happen again and again throughout the entire summer, and the company would say nothing is wrong. I finally decided to give up, until this summer, when it happened again, but worse. I live in florida and it got to 85 degrees in my house!!! I decided to call another company since I am no longer under warranty for labor with the company who installed it. They came out and checked everything, the pressure, air handler, freon, leaks, compressor, thermostat, filter, and said that they couldn't find anything wrong either. They did notice that there were a couple of small leaks in the ducts, but told me that shouldn't make the temps that much warmer. The A/C did stay at the temp that I set it at too that morning, but right after he left, the temp went up 2 degrees higher. I called him back and told him to look again. He still couldn't find anything, but suggested it could be that the ducts are too small for the new system. I was desperate and said, lets do it. Today they just installed a 18" duct at the air handler and supply unit, and fixed the leaks in the ducts. Cost me $425, guess what? It still doesn't work right! It was at 80 degrees all night at my house. They are coming back out tomorrow, does anyone think it could be electrical?

Thanks!
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Old 06-26-2012, 06:31 PM   #11
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New A/C unit won't cool in hot temps


My BRAND NEW home is doing the same thing!!!!!! What is the problem????
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Old 06-26-2012, 06:42 PM   #12
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New A/C unit won't cool in hot temps


1.) Are these complete brand new systems or just the outside condenser?

2.) Fixed orifice (piston) or thermostatic expansion valve (txv) refrigerant metering device? If fixed orifice, did the installer at the very least check the old piston in the evaporator to see if it matched tonnage size of new condenser if these were only condenser change outs? New condensrs come with a new piston to be installed into the evaporator to make sure the tonnage matches BUT you have to have a compatible evaporator.

Here's some goOd information on txv's.
http://www.udarrell.com/txv_applications_subcooling_superheat.html
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Old 06-26-2012, 06:46 PM   #13
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New A/C unit won't cool in hot temps


It's a 6 month old home!!! Just started doing exact same thing as above!!! It's 104 out side now!!! My ac is on 70 it's 80 degrees!!! My dog is even hot!!!! A/C company has been out here numerous times!!!!
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Old 06-26-2012, 06:53 PM   #14
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I'm betting the install was crap, no vacuum was pulled but rather the lineset/system was purged thus leaving air in the lines with the refrigerant.

New homes do not mean quality install. Nor does hit mean a quality heat load calculation was performed to determine correct sized a/c system for the home if it was performed at all. Nor a manual D, duct work design and install.

How it works on new construction/new sales homes is put it in, sell it and then it's the new home owner's problem.
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Old 06-26-2012, 06:54 PM   #15
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New A/C unit won't cool in hot temps


Quote:
Originally Posted by Newhome1 View Post
It's a 6 month old home!!! Just started doing exact same thing as above!!! It's 104 out side now!!! My ac is on 70 it's 80 degrees!!! My dog is even hot!!!! A/C company has been out here numerous times!!!!
Ask the A/C company who installed the A/C and ducts that you need to see the Load calculation.....If they don't have it.... you ask how they get all the informations about the duct sizes, A/C size etc

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