Poor cooling, not very old outside unit evidently performed well

House of about 1800sf had a 2.5 ton outside unit manufactured in late 2005 that seemed to perform well when the AC was run, but did not cool the house very well.

The refrigerant line was very cold and the air being blown out of the outside unit was noticeably warm, consistent with a unit that is performing very well; but the air coming out of the supply registers never got below 59F, and the house was not cooled so well. The outside air temperature in the mid 70s and the outside unit was in the shade, and not significantly obstructed.

However, supply registers on the 1st floor level were about 2/3 blocked with sheet metal that was screwed in place, and subsequently over-painted, evidently to direct more flow to the 2nd floor.

The supply air temperature was measured at a 2nd floor register that had the best outflow.

Is such supply duct blockage likely to affect the cooling performance in such a way?

Any other theories as to the reason for this apparently odd behavior of the system?

Frank, that unit sounds like it was designed “not to work”.
You can not properly condition 2 floors of a building with 1 unit without the proper design modifications.

#2 the air entering the unit is just as important as that going out. What was it, and what was the wet bulb temperatures of both?

#3 what was the outdoor air conditions at the time of test?

Thanks for the reply, David.

The outside air temperature was in the mid 70s, as noted, and it was breezy and somewhat humid, though not extremely muggy, with variable cloud cover, moistly sunny through the clouds. Some thunderstorms were reported in nearby areas, but no rain occurred during the inspection.

Measurement of wet bulb temperatures is way beyond the scope of an inspection such as this, which took 4 hours as it was. The unit did seem undersized, given the construction of the house, being a colonial built around 1940 with 2-story rear addition which was built in the early 1990s according to the owner.

Frank, You hit the nail on the head!
HVAC evaluation “is” beyond the scope, so if your not going to take those measurements, there is nothing further to discuss or put in your report.

Also please do not burden the seller or your client with “Recommend further evaluation and repair by some HVAC guy that did it wrong in the first place”…