Carrier Infinity system operation questions (long post)

Hello group.. We have a new house with a Carrier Infinity HVAC system and I need to run some things by someone(s) who are familiar with it. The outside unit is the 38TDB condensor unit, and the VS8000 variable speed furnace with the infinity control thermostat. We moved into the house in late november so didn't really use the AC much. The last few days were unseasonably hot for this time of year here in central Texas (90-94 degrees) and last sunday I set the unit to 75 degrees (house was maintaining 77 prior to the adjustment) The unit switched up to high speed and ran and ran for most of the day and never was able to satisfy the 75 degree setting. Once it reached 75, the unit kept switching back and forth between high and low speeds (both compressor and fan) but couldn't satisfy the setting of 75 degrees. I have noticed it doing the same thing yesterday, when we got home it was running on high and the house was 76 but the unit was not able to satisfy the swing to bring the house below 76. Again, it kept switching between high and low. I checked the filter monitor which this unit measures pressure so figured it should be pretty accurate, and it showed 71% used. I went upstairs and checked the filter, it did show dirt but easily shows light thru the filter. I went ahead and put in the new one (original from November, but these are supposed to last 6+ months and the installer told me the unit will tell me when to change it) Also, Carrier brags about how quiet the compressor units are, but when this unit starts, it's VERY loud(buzzing from the compressor), and quiets down as the pressure increases..Is that normal? I had a Lennox that was much quieter... I am not looking for advice to fix the unit myself, but trying to find imput from people who have these units or install/service them, to see if what I am experiencing is normal, or if I should call out the company that installed it..I don't want to call them if the unit seems to be working normally..I know this system doesn't operate like a standard unit. I know it's supposed to be a really good system, but not ever having one I don't know if I should worry or call the contractor..The house has the best insulation we could get, has tech shield decking and low E windows so the unit should have no problem cooling the house if they sized it right..The house is about 1625 sq foot one story..I can't remember if it's a three ton or a four ton. I know you can't tell without a manual J if it's correct or not but here are the numbers:
Condensor part#38TDB048300 Furnace#58CVA110-20
Thanks alot for any recommendations...
John
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The 048 in the condensor suggests it's a four ton unit.
That oughta be plenty enough cooling -- or more than enough. The fact that it's running at h igh speed and can't cool your house says there is definitely something wrong.
without being there, I'd suspect one of a couple things. The condensor might be dirty, there may be a restriction in a refrigerant line (clogged orifice, or somethign clogging the filter dryer). Or might be old fashioned low on freon.
I'd talk with a couple neighbors, and see who they use. If they have had a good experience with them.
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Take a thermometer and check the discharge air temp off the condenser outside. Then subtract the outdoor temp from it. What is the temp split? You way be drawing hot air from the attic or have duct air leaks. The system could be overcharged. http://www.udarrell.com/airconditioning-excessive-airflow.html
There is somewhat of a condenser Temp/split guide on my linked page. http://www.udarrell.com/ac-trouble-shooting-chart.html Check out the other pages for more information. Can not tell from here. - udarrell - Darrell
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