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Old 08-04-2011, 06:07 PM   #1
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Need some tips on getting my A/C colder


I have a 12 year old trane XR12 5 ton AC system, my home is 2400sqft. I live in Dallas Texas and temps here have been about 100 to 110 the past few weeks. I noticed my A/C will not get down below 80 so I checked the return air temp and it was 82 degrees and the closest outlet vent to the attic evaporator coil is 67 degrees and the farthest vent from the evaporator is 73 degrees. I called a A/C guy to come out and give it a check just to see if anything could be done to get it any colder. He claims he put 2 lbs R22 in but he did not have a scale so I know he just guessed. I figured he might have added 1/2 lb at the most as I know my system wasn't 2 lbs low. He claimed the superheat right were it needed to be. The work he did doesn't seem to have helped at all.

The question I have is is there anything I could do to help this system out.
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Old 08-04-2011, 06:18 PM   #2
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Need some tips on getting my A/C colder


flush the outdoor coil with a good strong spray from a garden hose sprayer not a pressure washer.
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Old 08-04-2011, 06:18 PM   #3
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Need some tips on getting my A/C colder


He didn't add 2 pounds. To improve your system you need a better house insulation or just wait like everybody else.
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Old 08-04-2011, 08:22 PM   #4
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Need some tips on getting my A/C colder


yuri I flushed the outside coil about 2 months ago and when the A/C guy was here he recommended the inside coil be cleaned also, he said he would only charge 350 if he didn't need to remove the coil and 650 if he did need to remove it. I bought the recommended cleaner and went up today and started taking stuff apart until I got to it and cleaned it. It wasn't dirty at all but I cleaned it anyway.

JJboy So you are saying this is about as good as it can get right? House has 14in of attic insulation, and I had 1in insulation board added to the exterior before they bricked it when I had the house built. Not sure if more insulation would fix the problem.
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Old 08-04-2011, 09:23 PM   #5
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Need some tips on getting my A/C colder


Quote:
Originally Posted by 737mechanic View Post
yuri I flushed the outside coil about 2 months ago and when the A/C guy was here he recommended the inside coil be cleaned also, he said he would only charge 350 if he didn't need to remove the coil and 650 if he did need to remove it. I bought the recommended cleaner and went up today and started taking stuff apart until I got to it and cleaned it. It wasn't dirty at all but I cleaned it anyway.

JJboy So you are saying this is about as good as it can get right? House has 14in of attic insulation, and I had 1in insulation board added to the exterior before they bricked it when I had the house built. Not sure if more insulation would fix the problem.
...this week the AC is suffering
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Old 08-04-2011, 09:55 PM   #6
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Need some tips on getting my A/C colder


Phack, I need to increase my evaporator coil cleaning prices. I'm doing condensers for $175, evaps for $150. Not sure why people need to pull out evaporators to clean them. I install an access panel for $45 and then do it if it's an accessability problem. Upflows I just lift and strap about a foot up and then clean. Never had a reason to actually have to break the copper lines for a cleaning.

Here's one I did this evening. Unless you (or whomever cleased your condenser a few months ago) had the condenser torn apart and looking like this, it was not cleaned correctly.







You see all that dirt coming out? Water won't remove that, the internal dirt that's caked and baked onto the hot coils.

Clean as a whistle, a ten year old whistle that's been sitting outside in the weather, that is. I dropped 85 head pressure with just the cleaning and dropped three degrees supply air.

Last edited by Doc Holliday; 08-04-2011 at 09:58 PM.
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Old 08-04-2011, 10:26 PM   #7
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Need some tips on getting my A/C colder


Yes I took the condenser apart and sprayed it with condenser/evap coil cleaner that I bought just for that job. After letting it sit for a while I rinsed with a water hose and spray nozzle set to a medium pressure. The fins on the trane xr12 are like little hairs and you have to be careful not to bend them over. After I was done cleaning the condenser looked like new.
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Old 08-04-2011, 11:49 PM   #8
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Need some tips on getting my A/C colder


OK First,the delta t should be measured just before and then just after the inside coil.The temp differance should be between 18 degrees and 22 degrees.
The tempatures between just after the inside coil and at the supply grill should be between 3-4 degrees.differance. Yours sound like they are between 5 and 14 degrees. in order for your temps to be true I would expect either the runs are not insulated or there is a break in the runs letting hot air to enter into the run air flow. my guess is that the whole duct system needs to be sealed and insulated.
Then and only then can a super heat or sub cooling number be calculated.
The two pound figure he gave you,he pulled out of his as* er back pocket and he didn't do the super heat calc.
When I measure things,I like the indoor coil to be between 38 and 45 degrees,even better between 42 and 45.
One last thing is that if you were 2 lbs low.where did those lost lbs go? You must have a leak which means you can expect to need gas every year unless the leak is fixed.That can get expensive.
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Old 08-05-2011, 11:28 AM   #9
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Need some tips on getting my A/C colder


Your delta T is between 9 (82-73)and 15 (82-67). an average of 12. that is too small. you want to see at least 16. As mentioned by REP, you need to seal and insulate the ducts, from 15 down to 9. it is a too big of the drop.
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