AC will not cool below 82 during the day

[Arizona_Mike]

I'm having a problem with my ac not cooling down below 82 degrees during the day. Evenings after the sun goes down, it will then cool below 82. I am getting only about 13-14 degree differentional between the return and the vents. I live in the Phoenix area.

The ac unit is a Trane XE1000, 3ton, 10 seer and is 13 years old. 1300 square feet single level house. Split unit with the air handler in the attic. New return air filter. Called service and they came out and checked the pressures. Said it was a pound low. Added the pound, checked the electronics and cleaned the condenser coil and said everything checked out. Same problem.

2nd service call, they checked the pressures again and said they were in the norm. Checked the air handler, blower is clean as is the expansion coil. Checked the ducts and no leakages. Same problem.

3rd service call, different tech, again checked the pressures and they were in the norm. Spent about 3 hours checking other things and couldn't find the problem. Wanted to remove all the freon and add new. Scheduled another service call.

4th service call, they removed all the freon and added new. Same problem.

So I guess my question is, what now? I am going to call a different company and have them check the system out and see if they can find anything. Is there anything I can suggest to them to check out?

Any help would be greatly appreciated.

Mike

[ckone180]

Sorry about the problems. You should really get another eyeball on it. Truthfully, a pound of refrigerant will not do that much for your system, unless it was teetering on the brink, and was not needed. Too many times I hear of "it was a pound low."

[Chuck Harwell]

After a good life a compressor is going to pump what it can and thats it.Pressures can be in the norm and still have a dying unit.

[Senior Tech]

that a reputable, qualified company with good technicians could easily find the problem...where's Payson when you need him...:confused:

First thing that pops out to me though is what is the return air temp at the grill verses the actual return air temp at the unit?

[coreymac304]

Your Drop Should Be Closer To 18 Degrees Not 14. Speed Up The Blower Speed.

[dan sw fl]

. I live in the Phoenix area.

The ac unit is a Trane XE1000, 3ton, 10 seer and is 13 years old. 1300 square feet single level house.

I am going to call a different company and have them check the system out and see if they can find anything.

Is there anything I can suggest to them to check out?

I would have them review Your check book initially.

[hvacrmedic]

Pressures don't actaully have a "norm". There is a "normal range", but that range is large enough to let the tech think that the pressure is ok when it isn't. For instance, if suction pressure is 75, he might think that it's ok. But depending upon the system match up the correct<sic> pressure might be 65 or even 85. Pressures alone cannot be used to evaluate system capacity or condition, unless they are obviously outside of the normal range. If the system has an expansion valve metering device on the indoor coil, then the system can be undercharged and still show pressures in the normal range, while capacity can be reduced significantly. If the techs aren't checking liquid line subcooling, then this could even be the actual problem. Superheat is also an important measurment. Ask the next tech what values he measured for these. If he looks at you like you're crazy, then you can refer him to this thread.

[Shophound]

Your Drop Should Be Closer To 18 Degrees Not 14. Speed Up The Blower Speed.

Speeding up the blower would have opposite effect on temperature difference across coil...decreasing instead of increasing. Lower airflow = wider split. Higher airflow = lower split.

I don't think this is the initial tack I'd take with the OP's system with the symptoms given. If the system always worked correctly until now with everything set as is then whatever has changed needs to be found and remedied.

[AcDOCnTRAINING]

The HVAC MEDIC is right pressures are not a standard for troubleshooting. Pressures are affected by temp.!
I noticed two things in what you wrote. First, nothing about checking the evaporator coil & second the tech added a pound of freon! If he did not perform a superheat (10 seer most likely have a piston metering device). The refrigerant levels could of been fine, howerver if he guided him self by pressures if your coils are dirty and not enough air is coming across the evap coil. This would cause your suction pressure to drop, making him think your low on refrigerant when your really not. Your delta temp. would also be low since the heat is not being removed properly out of the air. I would first call the company back, ask them if they inspected the evaporator coils i bet my money they did not! I don't care how bad your problem is, it should not take 4 service calls to figure it out!:eek:

If by any crazy miracle you do have a TXV in your unit then he should perform a subcooling not a superheat. A TXV will maintain a constant superheat! Hope you get it fix quick I hear the sun is two feet away from your head out there!

[AcDOCnTRAINING]

After a good life a compressor is going to pump what it can and thats it.Pressures can be in the norm and still have a dying unit.

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:confused: I would like for someone to explian this too me please!!! :eek:
If a compressor is runing with good comp.ratio & good pressures its doing its job period! Anything going wrong in the unit will reflect on the compressor!

[beenthere]

Evap coil may not be as clean as they think or say.

Some techs will say a coil is clean when its not, if they don't feel like working in the attic that day.

[vibration]

I dont know what's the norm pressure they got. When the room temp is high like 82, I think the pressure, especially the suction pressure, should be higher than norm. The TD you got between return and supply vent around 13, and the room could not be cooled down any more. I think restricted air flow or too much load may cause the problem.

[AcDOCnTRAINING]

I dont know what's the norm pressure they got. When the room temp is high like 82, I think the pressure, especially the suction pressure, should be higher than norm. The TD you got between return and supply vent around 13, and the room could not be cooled down any more. I think restricted air flow or too much load may cause the problem.

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Why would that be the case if the units has ran fine for 13 years? Yes, if the room is hot you would normaly get a higher suction pressure(unless you had a TXV), but the tech did'nt.He had such a low suction he added refrigerant. If the coils are dirty which they probably are he would have a low suction cause of poor air across the coil! The heat transer is being interupted thats why he is getting a low TD. Unless the insulation in the house has been compressed or removed or he added something with a great heat load to the house I very much dought that the load has increased.

[vibration]

His TD was 13~14, between return and vents. We need 15~20 TD at evaporator. It's pretty close. The H.O could not cool the house down below 82 with that TD during the day but could during night. That's why I doubt there may be not enough CFM or too much load.

[davo]

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Why would that be the case if the units has ran fine for 13 years? Yes, if the room is hot you would normaly get a higher suction pressure(unless you had a TXV), but the tech did'nt.He had such a low suction he added refrigerant. If the coils are dirty which they probably are he would have a low suction cause of poor air across the coil! The heat transer is being interupted thats why he is getting a low TD. Unless the insulation in the house has been compressed or removed or he added something with a great heat load to the house I very much dought that the load has increased.


Even with a txv, a high sensible load will cause a "higher" suction pressure.

The fact is, proper measurments have not been recorded.
They need to measure at least the Holy Trinity of HVAC. Superheat, sub-cooling, and TD at the air handler/coil. They also need to find out what type of metering device there is. Terms like normal, high and low, are all rather ambiguous.

I would guess a txv is starting to go bad, or a possible restriction. With out proper measurements, this is only an educated guess. All the sysmptoms are there. Some-one adds refrigerant to "get the pressures up", without knowing why, and the system still does not work.

A good tech will have no trouble finding your problem.

[frank slusher]

you should check the t-d at the coil not the vent, a lot of heat gain and loss can happen in a 150 deg attic. have seen quite a few broken compressors that still pump but don't cool very well, the last 3 had a little charge added shortly before the crash. 2 of them had twice the factory charge.

when you don't know where you are going stop and ask directions.