can't keep a/c in the room...

[PoolGate]

2 years ago I had my 17 year old A/C systems (2) replaced from builder's junk (Bryant) to top of the line Lennox. Last year was no issue. This year it seems the room won't stay very cold. I usually set it at 68 at night and once we are up it goes to 76. I have it crank back down to 68 for sleeping at night. It was not getting to 68 so I changed the schedule so it would only go to a high of 73. All day yesterday it ran from morning until night slowly increasing temperature in the room. By bedtime it was around 79. Then it slowly started going down again by the time morning came around it was finally at 68. I measured the temp coming out of the vents and it is not bad at 65 (outside temp is 90ish). Air flow seems normal. Filters are replaced regularly. This is an attic unit the attic gets hot but this has never been an issue before. It is under full warranty for 10 years so I called and they are coming tomorrow to take a look. Any ideas? I can not stand to sleep when the room is sweltering hot I am dying over here! The main floor A/C has no issues it works like always.

 

[Tamlibtoim]

Compare the temperature of the air going into your return where the filter is, to the air coming out of the nearest register. It should be a 15 to 20° drop. Based on what you were describing it sounds like you might be low on refrigerant with a 65° temperature at the registers even though the room is 68°. That’s only a temperature drop of about 3°. Of course there could be a number of other things wrong, but that would be my first guess. Second guess would be return air leak, sucking hot air in from the attic somewhere.

 

[Texas Splash]

Recently one of my units would run almost non-stop. When it finally stopped, it only did so for about 5 minutes, then it would run for a long time as if it couldn't maintain the desired temp. In my case it was my TXV valve (Thermo-Expansion valve). It's brazed-in the lines up where your evap cooler is in the attic and regulates, the flow of Freon - kind of like a car T-stat. They can stick or go bad. When it does, Freon isn't flowing quite as well as it should (or too much) throwing-off the temp-split readings (hi & low side) that effect efficient cooling. Odd that a unit only 2 years old would have that problem, or any other for that reason, but things happen. At least you're with a top name and should have a good warranty to cover whatever it is.

 

[PoolGate]

Compare the temperature of the air going into your return where the filter is, to the air coming out of the nearest register. It should be a 15 to 20° drop. Based on what you were describing it sounds like you might be low on refrigerant with a 65° temperature at the registers even though the room is 68°. That’s only a temperature drop of about 3°. Of course there could be a number of other things wrong, but that would be my first guess. Second guess would be return air leak, sucking hot air in from the attic somewhere.

The return is in the same room. The room temp is like 77 and the air coming from the registers is 65. It seems like it should be fine but the room barely cools at all.

 

[Tamlibtoim]

Sounds like you’re getting a 12° split, that is still not enough to cool efficiently. Hopefully you have a parts and labor warranty. Even if it’s under a part warranty you may still have to pay for labor.

 

[ajw22]

We have had hotter temps in the Northeast this year then the last 2 years. It sounds like your AC unit may be undersized and can’t keep up with the daytime heat. An attic may require more BTUs for its room size than a downstairs room.

Is your AC unit cycling during the day as the room temp rises? I suspect not. Yes, you do need to check if the unit is running at optimal efficiency. If it is then it means the cooling BTUs the unit is putting out is kess than the attic heat load in very hot weather.

Are your in and out registers at opposite ends of the room?

 

[Arizonarob]

PG, you have a great brand and a great warranty, don’t sweat it! ( See what I did there )
I’m getting my system changed out next week with a Lennox as well. The current Lennox system is 20 years old, and it’s getting tired. You can only really ask an a/c system to cool 25-30 degrees cooler then outdoor temperatures. It’s not a refrigerator.
This may sound stupid, but is a window cracked open somewhere? Check top AND bottom windows. I can’t tell you how many times my wife would open a window, and then not secure the top portion of the window when locking it. Just a little crack was enough to drive up temps!

 

[PoolGate]

Just to be clear the unit is in the attic but it cools the top level which is bedrooms. There are 2 returns one in the room and one outside in the hallway. Both 24x24. First thing I checked is for a window cracked.

Warranty is 10 years parts and labor.

No cycling at all it's just on continuously.

 

[ajw22]

Upstair bedrooms with air handler above in attic. Got it now. Is the compressor outside at ground level?

What temp is the lower level when you are trying to get the upper level to 68 or 73?

Heat rises and cold air falls.

In very hot weather I need to keep my lower level about the same temp as i want the upper level. Otherwise the warmer lower level heat rises to the upper level and cold air in the upper level falls. In effect the upper level AC is being asked to cool both levels, which it is not sized to do.

 

[PoolGate]

Compressor is outside ground level. Downstairs is set at 75 since the ductwork was not sized properly when the house was built. All upstairs rooms are fed by the upstairs system. We keep all upstairs doors closed in the summer and opened in the winter.

 

[ajw22]

I use an infrared thermometer to check on the output temp of my AC. My 2nd floor unit is putting out 56 degrees tonight. Anything above 61 degrees output on my unit indicates a problem. Usually low refrigerent.

 

[PoolGate]

I use an infrared thermometer to check on the output temp of my AC. My 2nd floor unit is putting out 56 degrees tonight. Anything above 61 degrees output on my unit indicates a problem. Usually low refrigerent.

Yep same thing an infrared style thermometer. The company is coming today to take a look but the solution may be simpler than I though. When I went up last night the thermostat was dark. I jiggled it around and it came back on and booted up. That wasn't the first time that happened. It is one of those fancy Honeywell computer controlled WiFi systems. When it goes down of course everything shuts off. When it comes back up it takes around 10 minutes for everything to work again. Hopefully that is it. I'll have him check refrigerant levels also.

 

[PoolGate]

The repairman just left and added about 2 lbs of refrigerant and fixed the issue with the thermostat cycling. He had thought when it was originally installed they may have not charged it all the way. I have a very long run from the attic to where the outside unit goes. His thermometer doesn't lie though when he was done the temps were around 7-8 degrees cooler coming out of the vents. So looks like I wasn't crazy after all!

 

[kairus00]

The repairman just left and added about 2 lbs of refrigerant and fixed the issue with the thermostat cycling. He had thought when it was originally installed they may have not charged it all the way. I have a very long run from the attic to where the outside unit goes. His thermometer doesn't lie though when he was done the temps were around 7-8 degrees cooler coming out of the vents. So looks like I wasn't crazy after all!

He added more refrigerant, but didn't fix any leak? Your A/C won't lose refrigerant if there's not a leak, it should have the same amount of refrigerant it had 2 years ago. If it cooled properly for the last 2 years, then it sounds like you have a leak!

 

[PoolGate]

He added more refrigerant, but didn't fix any leak? Your A/C won't lose refrigerant if there's not a leak, so it sounds like that was just a temporary fix.

No as I said it is a relatively new system and it was his belief that they did not charge it enough to begin with. He said if the issue comes up again, he will look for a leak.

 

[Texas Splash]

He said if the issue comes up again, he will look for a leak.

Hopefully you don't have a leak. But in the slim chance he does have to come back, mention the TXV valve. It throws some techs off target because of the symptoms. I know because the first tech who came to my place added Freon thinking the same thing (low), until his boss came back and educated him about the TXV influence on split temps and meter readings. Good luck and have a great weekend.

 

[Tamlibtoim]

If it’s cooling after he added refrigerant it will not be the TXV. If it were, it would still not be cooling. You definitely have a leak, should not have to add refrigerant especially if it was cooling fine before. Most likely leaking in the evaporator coil, almost all manufacturers have issues with the evaporator coil failing.