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I. We should have 17 to 20 degrees difference in supply and return.Possibly slightly low on refrigerant.
2. If charge is correct they might not have changed metering device on indoor to work with the R410A properly causing refrigerant to flash too late and therefore not pick up enough heat .
3.My suggestion would be to get a new tech in to first of all check the charge and then make sure metering device is correct.
Both of these will be identifiable by connecting gauges and watching pressures.
1. How many square feet upstairs ,how high are ceilings and are there a lot of windows?
2. Ductwork definitely needs to be insulated
I am speaking of wrapping.Ducts should be wrapped with a 2" vapor bearing .I am thinking also the 2 tons is slightly small.The only way to know that is to run a load calculation on the structure but as a rule of thumb a two ton unit is good for about 800 to 1000 square feet.
An attic exhaust fan would probably help some.If you can get the attic air down from 120 to 130 on a hot summer day to 95 to 100 will make a tremendous difference.
AS for a third system, you might consider installing what is called a mini split to help out on these hotter days
Here is my suggestion.Have another contractor come to give you an "estimate" on replacing system.Ask them to do a load calculation for you to determine what size is actually needed .If indeed a 2.5 or 3 ton is needed,ask about a trade allowance on your 2 ton system. Also have them do an analysis and evaluation of the ductwork.
If you have further questions, please let me know.
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