newly installed central ac Options

Hi everyone, I got my central ac installed recently. i have nearly 2K sqf 2 story house and contractor said that trane 2 1/2 ton should be enough to cool it at summer time. They also said that they guarantee 20F difference after ac is on. Well, i run it now and can't get even 5F difference in the house.. i'm just wondering what is the normal expectation from 2.5 ton unit should be? can it perform to cool down temperature till 70F when outside temperature is 80-85F? there is no icing on the pipes coming out from compressor i don't know there should be any ice at all... i'm kinda disappointed with it especially remembering that i paid $4k to install it.... Thanks D
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Djavdet writes:

"Difference" between what?
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I did not ask them specifically but assumed that it is before unit is on and after.... anyway the contract explicetely says : design tenperature: 70F on a 90F day for cooling.
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Twenty degree drop is about normal and that size AC is common on houses your size.. If you are getting only 5 degrees, something is wrong. Call the installer and he'll come back and fix it.
There should be no icing on pipes. The coil should be getting cold though.
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Djavdet wrote:

Do you have good air flow? What is blower size(in Hp)? My house is R2000 spec 2.4K sqf 2 story. 3 ton unit is just doing fine.
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It looks like i got 1/2 Hp blower. It's 12 years old but heats the house ok, i did not complain. How fast can you get 10F drop in your house? D
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What was the temp outside today? What was it in your house at the same time, after the AC had been on for at least 4** hours.
**I don't know how long it should take, and I don't even know how big my ac is, although it's written down here somewhere.
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ac was on all day..outside temperature was 95F and inside is about 89F it really started go down when outside temperature lowered.. so it all looked to me that the ac thing only can cool down the house when the outside temperature is low enough... that's i started questioning the whole installation... D
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Djavdet wrote:

You give no indication where you are, or what the humidity is.
The "20F difference" of which they speak is probably between the inlet and outlet of the unit. If they've guaranteed it, and it's not happening, then call them up and make them get it right.
All that said, I think you probably should be able to cool a well insulated 2K ft^2 house effectively with that size unit in most parts of the country. On really hot days it might run constantly, but that's when it is most efficient.
As a point of reference, I have a somewhat larger house in Texas, and my 4 ton unit is probably over-sized, judging by how little it runs.
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have good insulation in the house. This time of year it is maybe 85 to 90 deg in the hotter areas. You should be able to get to 70 deg without any problem.
My house is slightly under 2000 sqft and I have a Trane 2.5 ton heatpump and it has no problem getting to 74 deg on the 95 deg days of summer, and I keep it on 70 to72 deg in the winter with no problem or having the heat strips kick in.
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BTW, the people here all agree in prior threads that it is not good to put in too big an AC either. So it sounds from the others like you have about the right size, so if that is so, don't be thinking I could have just gotten a bigger one and that would have solved it. Too big has its own problems.

Sorry you did say what the outside temp was. And I was wrong to count on that so much, as CJT explained.

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A simple test you can do is to measure the temp at the return air intake and at some of the outlets. You should see a temp diff in the ballpark of about 16deg F. If it's way off from that, you have a problem.
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