forgot to add, the ductwork is original, and has been checked adn sealed for leaks. they said the ducting was fine, as i have 12inch mains and each branch is a minimum 8 inch. only one branch has 2vents on it, the rest all run straight from the vent to the main trunk.

Yeh, the direct sunlight will make it warmer. Options are plantings, or shade structure. If you go with a structure make sure you don't inhibit air flow. I tooled around with misters on the coils once but it was too much trouble and wastes water. Shade is your best bet.

How about a trellis for shade? This will help with shade but not restrict air flow.

Question for you to ask the tech: What are your superheat and subcool readings on the new Trane? The subcooling determines system charge while the superheat determines the refrigerant flow in the evaporator coil.

You can also post your question on HVAC-Talk.com. They can be a little rough sometimes.

Best of luck.

i thought about shading it. funny thing is, if we had put up a wood fence with our tax refund, instead of buying a new 3000.00 couch my wife had to have, it would be shaded!

D&K:
Another question for your HVAC tech (or for you): What is the "split" temperature measured on your evap coil? The "split" temperature is the difference in temp between the supply air (just before the evap coil) and the cooled air (just after the evap coil). Should be about 20 degrees. If the house is very humid, the split can drop to about 12 degrees as the coil is removing a lot of humidity.

"forgot to add, the ductwork is original, and has been checked adn sealed for leaks. they said the ducting was fine, as i have 12inch mains and each branch is a minimum 8 inch. only one branch has 2vents on it, the rest all run straight from the vent to the main trunk."
D&K does your main duct reduce down along its length after the take offs or does it stay 12 inches throughout?
Also, that tech, when he blew some of the excess charge did he recheck the system using the sub cool/superheat method or did he use the SOHP (seat of his pants) method? Did he check the inlet and discharge air temp through the condenser. Something tells me this tech might have been on the right track but his little choo choo can't pull a full load yet.
A little hint for anyone who has their system serviced during the season and the tech makes reference to the charge being off and he adjusted it. Kindly thank him and looking him straight in the eye ask him "whats my systems superheat" or "whats the subcooling temp"? Most of the time you will probably get a surprised look and a BS answer. Then you can call him on his comment.

all i can tell you is he put his gauges on it and saw the pressure was too high and recovered some freon. he said he may have to put a little back in, but he did not.

AFAIK he did not figure the SC/SH unless he could figure it in his head.

as far as the split, the only time it has been checked is when i did it one night. i don't remember the exact values, but i do know it was around 19 or 20 degrees. i have not checked during the day. the tech never even went inside when he was there, since at that particular moment everything was working as desired.

the main duct does go down to about 8 inch for the final 2 or 3 vents, but for most of them each vent branches right off the main 12 inch duct. there are 2 12 inch return ducts, one from the den runs about 40 ft and one from teh breakfast room is less than 15 ft run to the air handler.

the system does remove a lot of humidity, here lately we have had 105 degree days with 60% humidity. gallons of water flow from teh drain of the unit!

so any ideas what a 3.5 ton XL14i with a matched coil should run for SC/SH?

one final question. i know that if they up the speed of the blower that it will reduce the cooling of the air, but to me it seems like maybe the air is flowing so slow that it just cannot overcome the heat gain of the house. would it help to bump the speed up just a bit? it seems to me that all AC systems now blow slower to be quieter as well as remove more humidity, but i don't mind hearing the system as long as it keeps the house cool.

D&K:

Your first 2 statements above scare me. I don't think this tech has a clue how to charge a system by sub-cooling if it has a TXV. If it does not have a TXV, the system is charged by superheat. Even I know this and I am just a flunky homeowner.

I would call Trane and have them send a Factory Rep ASAP. You didn't spend $9k for this aggravation. You researched and planned your system thoroughly, now it's time for Mr Trane to figure out and solve your problem.

"so any ideas what a 3.5 ton XL14i with a matched coil should run for SC/SH?"

- Don't know about Trane but for my new 3 ton, 14 SEER, Goodman with a TXV, superheat is 7 to 9 degrees and subcooling is 5 to 9 degrees. You need a set of guages and an accurate digital thermometer to figure SC & SH.

"one final question. i know that if they up the speed of the blower that it will reduce the cooling of the air, but to me it seems like maybe the air is flowing so slow that it just cannot overcome the heat gain of the house. would it help to bump the speed up just a bit? it seems to me that all AC systems now blow slower to be quieter as well as remove more humidity, but i don't mind hearing the system as long as it keeps the house cool."

- Maybe the dip switches for the variable speed motor are not set properly? These are located in the air handler. Your concern about reduced air flow is one of the reasons that I went with the good old 3-speed motor in the air handler and stayed away from the v-s motor.

Do call the Trane rep. He/she will tell you that they do not assist homeowners, but that they do assist contractors who request it. If possible, tell the rep your problem and ask that the contractor be assisted. It might work. It did for me.

"the main duct does go down to about 8 inch for the final 2 or 3 vents, but for most of them each vent branches right off the main 12 inch duct. there are 2 12 inch return ducts, one from the den runs about 40 ft and one from teh breakfast room is less than 15 ft run to the air handler."
If I'm reading this correctly D&K it appears for starters you have an air flow problem. You should have that checked out. I ditto what garyg says about your two statements. That tech is probably a greenhorn. Oh as for the sub cool and superheat readings,, yes, those are standard,,, some equip. mfgs may like to see a degree or two up or down but these are typical settings and will give your system pretty much peak efficiency no matter who makes it.

You definately have a ductwork problem. 3.5 tons requires 1400 cfm MINIMUM in supplies and the same cfm from the Return Air. an 8" pipe gives you a TOTAL of 200 cfms (if 3 registers off one 8" main you get about 66 cfm out each register, NOT 200 off each) cfm in controlled by the total of pipe connected to.
The local Trane distributor WILL help you by coming out with the dealer who put it in as bus driver says above......
They should total supply and return cfms to ensure balanced and ensure main trunk lines big enough to do the job this deluxe unit should do for you. Going from a 3 ton to a 3.5 tons should alert a dealer that ductwork and return air most probably needs to be mondified for the extra air/tonnage. ie. A friend of mine keeps his MBR at 65 degrees on a zoned ductwork system and it's 101 here today...