R22 contamination or cap tube issue?

Old 06-26-15, 03:37 PM
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R22 contamination or cap tube issue?

Hi, I bought a foreclosed house, and the first day we moved in the upstairs AC was not working at all. It was blowing hot air, so I called an HVac tech that my wife knew and recommended. The guy came, he charged some freon in and the AC started to cool to about 70 degree (at the register). He said there was no leak, just a bit at the charge valve which he had fixed.

Now that we are in peak summer season, the air that's blowing out is about 70 in early morning, and 71-75 at all registers from noon to the evening. The system upstairs could not keep up with the heat; if I set it to 74, it would climb to as high as 81-82 in a hot day. In short, I asked the technician to come again to look at it, he and I agreed that the AC only cools the air by 5-8 degrees. He than told me that my AC is located in the attic which is 135F, and it is because of that, the AC isn't cooling well. I then argued that why is my downstairs unit (exact size/model/shape...), is blowing air out at 16-22 degrees cooler --- and he said that's b/c the unit downstairs in located in the basement, therefore, it would work better.

I really need to fix my AC since it is not blowing cool air. It has proper freon, and pressure (72psi on low, and about 270 on the high side). I have already accessed the evaporator coil and found the temperature of air at the coil to be 68F, and that it does not use a TXV valve, but instead capillary tubes. The tubes are small and long and I am suspecting the system is having one of these problems:

1. Capillary tube is bad (restricting a proper flow of freon to the evaporator coil) -- The cap-tube is about 20 inches long. Could it be the builder installed it wrong, since it could be alot shorter?

2. Capillary tube is clogged with oil or water vapor since the system does not have an inline filter before the tube.

3. R22 Contamination - At 72psi, the saturated temperature at the e-Coil should be about 45-54F, but when I measured it with a fairfield contact thermometer, it was more like 64F (right at the junction of the CAP tube & coil). I believe the freon in my system is contaminated with other gases (nitrogen/water vapor etc...), and hence the temperature isn't at the saturated temperature at the coil.

I am out of ideas; would someone please give me a feedback with what to do? Is it possible for capillary tubes to go bad (restricts the flow of freon)? Do you think I have R22 contamination? Thank you!
Old 06-26-15, 04:41 PM
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We don't discus pressures here. When you say cap tub with a "S" makes me think it's not a cap tub,which is mainly found in something like a window unit. Can you post a picture? Maybe your looking at the something different? Could wrap the body in a hot wet rag. If it's wax or moisture it will melt and clear up for a time. Good luck.
Old 06-26-15, 08:21 PM
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Sound like there is a problem with the duct work in the attic. Plenty of working systems with duct work in the attic. The tech you have appears useless.
Old 06-27-15, 03:57 AM
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Is the filter OK ?

Any problem with the air flow for the return air ? Is it sucking in Hot attic air ?

Any problem with the air flow of the supply air ? Any noticeable leaks ?

Id you do not have a thermostatic expansion valve , my guess is you have a fixed orifice / piston metering device ?

As has been said , photos may help .

Measure the outside air temp , the temp of the hot air coming out of the condenser unit , the temperature of the large copper refrigeration line leaving the coil in the air handler and the temperature of the small line leaving the condenser unit .

As you have discussed , re-measure the return air temperature and the supply air temperature at the first supply grill .

God bless

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