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Old 09-04-2011, 08:40 PM   #1
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We just bought a house, the air works but it just dont cool as low as I like. It will get down to 73 but just won't get any colder. I noticed the larger line from the outside unit to the wall of the house ( about 3 or 4 feet ) is not insulated, the rest of the line in the attic is insulated. Will that small amount of line outside uninsulated cause the unit not to cool proper?

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Old 09-04-2011, 08:51 PM   #2
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We just bought a house, the air works but it just dont cool as low as I like. It will get down to 73 but just won't get any colder. I noticed the larger line from the outside unit to the wall of the house ( about 3 or 4 feet ) is not insulated, the rest of the line in the attic is insulated. Will that small amount of line outside uninsulated cause the unit not to cool proper?

There is an hvac forum down below in case you want this moved or care to repost this down there but yes and no, a few feet of exposed low pressure suctin line will not cause the "problem" you are having. I quote problem because many people would love for their a/c to get them down to 75 let alone 73 or below.

What is happening is after the liquid refrigerant is shot up into the evaporator and it boils over, becoming saturated and now extracting humidity and heat from the living space air while in the evaporator, it is sucked back down into the compressor which increases the pressure on that now vapor. While it is on it's way back down the refrigerant picks up heat, some heat known as superheat. This is something the hvac technicians controls via refrigerant charge.

Too much charge and you lose superheat and thus capacity, too little charge and the opposite. On that note the line being exposed to the sun/outside will raise the temp of that refrigerant outside of our control and can make the charge unreliable and make it harder or take longer for the refrigerant to lose the heat it has extracted which can cause your system to not cool as well, why I said yes and no previously. If the refrigerant can not let go of the heat than it wil not be able to pick up as much either. Now we're talking a few feet versus the entire lineset so all in all it should and needs to be insulated like the rest of that line but is most likely not the main "problem" as it stands.

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Old 09-04-2011, 11:30 PM   #3
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Also, the vapor refrigerant with the use of the condenser fan bringing a certain amount of air through the condensing coil, the once passed through the compressor high pressure high temperature vapor literally condenses back into a liquid as it is cooled down.

One thing you can do is rinse the condenser off. Not with a pressure washer as you don't want to damage the fins of the coil but with some pressure, like your thumb over the end of the hose kind of pressure or with a normal handle for a water hose.

Knock that dirt off (even if you can not see it it is there) and the condenser stands a much better chance of doing it's job, condensing the vapor into liquid while dissipating the heat extracted from the living space into a space where it doesn't matter, outside.
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Old 09-05-2011, 02:49 PM   #4
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I don't think AC was supposed to go below 73 anyways??
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Old 09-07-2011, 08:13 AM   #5
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I don't think AC was supposed to go below 73 anyways??
Why not? I routinely dial down to 70 or even lower in the summer. Proper system design, sizing and install (charge) it will not be an issue. Really, setpoint is not so much the issue as outdoor ambient temperature, at some point you do have to be careful about liquid refrigerant flooding back to the compressor but that is more like in the 50-60 degree range and even that can be overcome using low ambient accessories.
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Old 09-08-2011, 03:23 PM   #6
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Had a similar issue recently. AC wouldn't keep up in the hot days. Had it checked out and everything was fine aside from my AC unit being 30 years old.
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Old 09-13-2011, 11:04 PM   #7
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Well first take of filter on unit. Freon lines are iced up...it may need more freon added to the system, or condensation drip lines may be backed up.

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