AC Not Enough Cooling

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Old 07-22-06, 10:48 AM
S
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Question AC Not Enough Cooling

I am a new AC guy. I met with an AC problem, and any advice is greatly appreciated.
The condensing Unit is a 2 ton Concord, model: 2AC13B24-1A, newly changed because the old unit’s (Ruud UAKA-24JAZ) compressor refused to start. The indoor A coil is the system’s original ADP cased A coil. The liquid line is ¼ inch and suction line 5/8 inch.
The problem is not enough cooling, the A coil never gets really cold, and the supply air temperature is never cold enough (only about 67 degrees) to cool the house.
The owner’s father who is learning AC noticed some pressure fluctuations and suggested some non-condensable air in the system. So I agreed, and we evacuated the system, flushed it with dry nitrogen, pulled vacuum, charged dry nitrogen to about 30 psi, pulled vacuum again for almost two hours. We recharged the system using weigh-in method. Then I noticed the suction line pressure was above 90, and liquid line pressure about 250 psi. These pressures are much higher than other systems I have serviced. The ambient temp was above 95 degrees (in Atlanta, Georgia), and indoor wet bulb about 71-72. The suction line temperature near the condenser is 61 degrees. I checked the evaporator coil (at attic); the coil is clean but not cold enough as expected, and the suction line at case outlet is about 56 degrees. I guess the problem is caused by the orifice or the capillary tubes are partially blocked, so not enough Freon is passing through and evaporating in the coil. So I suggested to check the check flow piston at the A coil and open the clog if any. Or we'd better change a new coil. But the owner’s father thinks the liquid line filter causes the problem since the original system did not have one and worked fine. So we should remove it. Also he suggested the ¼ liquid lines is too small and should be changed to 3/8 size, and I agree with that.
Since he is half step in HVAC field, and I have just stepped in this field, we cannot convince each other. We are seeking some more professional opinion to decide what to do next. Also is there a way to open the clogged capillary tubes. Any suggestion will be greatly welcomed and appreciated.
 
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Old 07-22-06, 11:39 AM
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Sorry, we do not offer the type of advice you are seeking.

sickac,

You need to be aware if you don't already know that you must be qualified and EPA certified to work on refrigeration sealed systems.

If you are new to the industry you must have had some formal training.
If you refer to the basics you learned in this training the answer will be obvious.
 
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Old 07-22-06, 11:53 AM
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Wink

My books show for a 2 ton 5/16" liquid and 5/8 "suc for up to 35 ft only. Yes there is a tool to clean out clogged capillary tubes. Some times if that are clogged it will get a ice build up on the tube where the block is, That high suc 90psi could be from the burn off when you just turned on the AC and the home is hot. keep the drier on the liquid line there. But you should know all this if your ESP

ED
 
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