# New A/C unit won't cool in hot temps



## harleyrider (Feb 20, 2007)

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


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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## bigMikeB (May 31, 2007)

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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## joee (Aug 14, 2007)

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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## jogr (Jul 24, 2007)

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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## rjordan392 (Apr 28, 2005)

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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## rjordan392 (Apr 28, 2005)

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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## BigJimmy (Jun 30, 2006)

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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## joee (Aug 14, 2007)

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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## Newhome1 (Jun 26, 2012)

*Hi my BRAND NEW home just started doing that!!!! a/c guys say there is no problem!!!*

:furious:


wishiknewmore said:


> 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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## Newhome1 (Jun 26, 2012)

My BRAND NEW home is doing the same thing!!!!!! What is the problem????


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## Doc Holliday (Mar 12, 2011)

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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## Newhome1 (Jun 26, 2012)

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!!!!:furious:


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## Doc Holliday (Mar 12, 2011)

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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## JJboy (Oct 12, 2010)

Newhome1 said:


> 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!!!!:furious:


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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## Newhome1 (Jun 26, 2012)

They are comming tmrw to look at A/C..I will get out my iPad and show them all of this so maybe they will have a clue where to start.. :sweatdrop::no::furious:


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## biggles (Jan 1, 2008)

go out and grab the LL raw copper line out on the condenser warm to hot? what the ambient days temp is,and is the condenser blowing heat into your face.if the unit cools anytime during the day and makes the setpoint it's the charge that isn't right..need a split on the the air handler not the registers.then are all your supply and return ducts sealed with mastic or duck tape...straight runs or flex duct all looped around...pix if possible


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## Newhome1 (Jun 26, 2012)

Ok so I called my husband and he told me to go see if the unit is running outside! It's not!!! He said to turn it off inside!! It's been running all day just the fan I guess??? What could be the problem?? Ac burnt out??


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## hvac5646 (May 1, 2011)

Newhome1 said:


> Ok so I called my husband and he told me to go see if the unit is running outside! It's not!!! He said to turn it off inside!! It's been running all day just the fan I guess??? What could be the problem?? Ac burnt out??


blown fuse


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## hvac5646 (May 1, 2011)

To the OP...with out subcooling and superheat readings we can only guess...

but I'm betting you have a partial restriction.


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## Doc Holliday (Mar 12, 2011)

hvac5646 said:


> blown fuse


 
If it were a blown fuse than there'd be no controlling the inside and that is working via the stat in cooling mode or at least that's what I'm led to believe. Stat is on cool, inside is on but not the condenser. 

It's going to be a pressure switch, compressor thermal overload, breaker, float switch, something specific to the condenser.


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## Newhome1 (Jun 26, 2012)

Ok so, heat and air guy is here, pressure switch when off, he claims when he put freon in the unit he got air in it and that's why it had not been properly cooling.. He is draining and putting more freon in now.. ??? He said that will fix the problem..


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## Newhome1 (Jun 26, 2012)

a/c guy was here earlier and left, he said all problems was because of the issue I said before.. He fixed it, so I put my a/c on 69 left for 6 hours and it won't get cooler than 75 in here.. Some say that's normal, I've never lived somewhere that you put the thermostat on something and it stays 5-7 degrees hotter! No matter where I lived..


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## wkearney99 (Apr 8, 2009)

Just how hot/humid is it in your area? An AC unit can move the temp only so far based on outside temperature.


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## Newhome1 (Jun 26, 2012)

107 Oklahoma.. Very humid..


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## tima2381 (Feb 24, 2007)

Is maintaining 75 inside when it's 107 and humid outside an improvement over the performance pre-service? In any case, it doesn't sound so bad to me...


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## Newhome1 (Jun 26, 2012)

It's not bad I just lived in cooler/more comfortable places in same town, kind of disappointing since this is my first brand new home and I get hot when I get ready! But you are right it isn't so bad..


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## tima2381 (Feb 24, 2007)

Others things to consider are shade tree coverage, insulation differences, etc. If there are any comparable houses around you, ask your neighbors how they're doing, but to get a meaningful answer, you'll probably have to measure temps yourself and wait until you know the system's been running an hour or two.


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## Newhome1 (Jun 26, 2012)

The houses right next to us just built as well, no problem with theirs, and it matches what they set it on.. Shade trees are a good idea..


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## tima2381 (Feb 24, 2007)

What do they set it on?


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## Newhome1 (Jun 26, 2012)

72 & 68 were most of them..


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## wkearney99 (Apr 8, 2009)

Also consider that using too low a setback during the day can be a problem. AC units can only do so much, and not always as quickly as people might like.


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## Newhome1 (Jun 26, 2012)

Ok thank you!!! I just got home and it's 70 in here and that's what it's set on Whaaahoooo!!!!! 106 out side!!! I was testing it!! I won't hurt it I will keep it on 72 thanks everyone for your help!! I'm going to talk to my husband about building some sort of shade for it!


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## Newhome1 (Jun 26, 2012)

:thumbsup::thumbup::whistling2:


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## wkearney99 (Apr 8, 2009)

72? Why so low? You're just wasting tremendous amounts of energy making the system work that hard. Put it at 76-78 and you'll be fine.


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## Newhome1 (Jun 26, 2012)

Well we like it cool... 75 is kind of stuffy...


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## picflight (Aug 25, 2011)

I keep mine at 79.


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## Newhome1 (Jun 26, 2012)

We know several who keep it higher and even low as 68.. 72 is pretty sufficient for us..


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## gregzoll (Dec 25, 2006)

I keep mine at 72 during the day, during the peak of the Summer, and 69 at night. Of course, I do not have a high gain, since I placed UV film on my windows.

My house has no insulation in the walls, but insulated in the attic with good venting, along with air leaks sealed.

The temp does not get to 73.5, until around 2-2:30 in the afternoon. It stays around 71, until around 11, then starts creeping up towards 73 by 3 or so.

So in reality, I am spending no more, but actually les, if I had it set higher. Plus I like to keep my electronics cool, along with our dog.


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## Newhome1 (Jun 26, 2012)

That's what we do as well!! Sounds like our house has some things in common  
And Ohhh how it feels good right now!! Thanks you guys for all of your help!!! :whistling2:


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