I believe he said "higher load rooms" vs. "higher charge".
Originally posted by chipper
What do you mean by higher charge rooms? The ones that are larger in size or take the brunt of the sun?
What he means is that rooms that have a higher heat load on them (from sun, door openings, larger expanses of glass, greater ceiling surface area, etc) will feel less cool more noticably when system capacity is reduced than rooms with a lower heat load.
An over or undercharge of refrigerant will reduce system capacity. If at any time a technician has tweaked the charge and did so by pressures only (or worse just put his hand on the suction line as he was charging until it got "beer can cold") then it's highly possible your system's charge is out of whack. This problem will only be aggravated if the system uses a fixed restrictor metering device rather than a thermostatic expansion valve, since fixed restrictor systems require a near critical charge (meaning it must be pretty much on the button for the system to operate at rated capacity).
You could have a compound problem. Airflow diminished to a few rooms combined with a tech who tweaked the charge, possibly influenced by a pressure reading that was off due to the airflow problem. This once again emphasizes why technicians need to make superheat and subcooling checks as much a part of their routine as carrying gauges in a service truck.
I'll repeat what I and others have said. If your system performed well for you for a year and then something changed, that something that caused the change needs to be found and remedied. Since the new ductwork didn't help matters any, the original problem is still there, waiting to be found.
The electrical problems appear unrelated to the performance issue. Sometimes these things crop up all at once, which seems confusing until someone with a cool head (no pun intended) sits down and puzzles through all the data to figure it all out.
Building Physics Rule #1: Hot flows to cold.
Building Physics Rule #2: Higher air pressure moves toward lower air pressure
Building Physics Rule #3: Higher moisture concentration moves toward lower moisture concentration.