I have a 3 ton R410A A/C unit that is 8 years old and is using copper lines that are too small. Does this cause leaks, diaphragm failure, and compressor failure?

The air was not blowing cold, so I had the refrigerant refilled. It works better but only blows about 12 degrees fahrenheit cololer than the intake.

I had a reputable company come out to diagnose. When the new A/C was put in 8 years ago, they used the existing lines in the wall and just attached the new lines (in the attic at the condenser unit and outside at the compressor unit) to the exiting lines. The existing lines were smaller than the lines that go into the machine.

New line on left, existing on right New line on left, existing line on right.

The tech told me that this causes the pressure to rise above what the machine can handle, which is causing several problems: creating leaks in the evaporator, blowing out the diaphragm, and over working the compressor. He said my compressor is working too hard and can die any moment.

He suggests getting a new unit as soon as possible (and is estimating 7,500 - 10,000 for install in my 1600 sq ft 1 story house). He said they would not repair this because of he condition. He tested my compressor, said it is over worked. He leaked some refrigerant and said it smells contaminated. He listened to the compressor and said he can tell it is working too hard. And they supposedly did an electronic test to confirm it was leaking inside the evaporator coil box.

Does this diagnosis sound correct? How long can I milk this A/C unit machine? Am I destroying the compressor by running it with the smaller copper lines?

1 Answer 1


If the lines are two small it will change the efficiency and work the compressor harder. It is tough to fully clean the old mineral oil out that was used in older units. If the R410 smells acidic this could be an indication that the old oil was still in the system and mineral oil and ester oil don't mix. If there is old oil in the system this can cause early compressor failure. I am guessing what he called a diaphragm is the throttle valve or TXV that regulates the flow into the evaporator this could be damaged and part of the reason your system is not cooling. There are many electronic testers that can detect R410 at very small levels if a leak could be located a bubble solution can pinpoint it and there epoxies that may be able to slow or stop the leak but silver solder is the best way (not on a charged unit though) . The possible acid in the oil has caused damage already and compressors are not reparable. I would run the unit until it fails with a full charge it may last the season and shop around for a new system (get several quotes for the complete replacement). I am sure they did not want to put there name on a system that is damaged and have you upset with them as well as the first company for trying to save a few bucks that cost more in the long run.

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