[Chemist1961]

It's 95 F outside,but sweating bullets cooking at 78 inside, yet I have the AC set for 73.
Problem seems to be air flow to upstairs with the new HE Carrier furnace.
The basement is super cool even with the vents closed. Last year with the old furnace I could just run the fan most days and move the air and it would cool down well even without the ac on.
I took the fresh MERV 8 filter out to see if the pressure to upstairs improves.
Also have floor baseboard return air vents through out upper two levels no RA in basement.
I haven't adjusted or made any damper changes since the new system was installed and the heat distribution was excellent. In fact I have taped and sealed ducts and boots to improve the flow. Do I need to do anything to tweak the AC distribution.? Should I fully open all heat vents to improve circulation?
Air is blowing cold, feels fine at the vents, just not getting high enough.
I have also improved attic and rooftop ventilation so the attic should actually be cooler than last year. So why is it so hot?:furious:

 

[Chemist1961]

Updftae still hot and sticky

Ok, figuratively speaking I am no longer COOKING.Thanks, but still to warm and sticky.
So its 5:45 a.m. It stayed warm outside all night but the main floor temp did drop to meet the T stat setting of 73, after removing the filter and running at auto with ac on through the night. I would say the basement must be hovering around 60 or lower, but the top floor has stayed warmer than the main.
So to rewind, last year with the old Mid E furnace, on a hot day I could just run the furnace fan, a single speed and move enough air upstairs to cool things, most times with the AC off. Yesterday the stat was set for cool, fan in auto mode temp programmed to 73. Stat was reading inside temp at 78. I closed the 4 basement heat vents to force more air upstairs, no big changes.

This year the old AC is clearly working but the new Carrier 80000 BTU HE furnace doesn't seem to be pumping the air upstairs at nearly the same rate whether I set the fan for auto or high speed with the ac on.
So I think the ac unit is working fine but I'm wondering if the new dc motor can still move enough cold air upstairs or if my vents need improvement. I understand the principal of the new HE furnace with multi speeds and the new Carrier stat

Should I have to change any RA capacity to adjust for the dc motor. If anything we were more comfortable with the heat the last 4 months so air circulation seemed fine with the furnace on.

My returns are in wall at floor level, unobstructed. I have no returns in the basement. I have improved attic ventilation through added soffit vents and new roof with increased rooftop vents, so the attic should be less of a heat trap as well. Through the winter, I have taped and sealed the ducting on several runs going to the top floor and have not messed with any dampers. I also sealed my rim joist. No other modifications.

I have a total of 5, 8x16" RA grilles at baseboard level , 2 upstairs in 650 feet 3 on the main in 1000 feet and none in the basement. Do I need to enlarge these grilles or move them to ceiling level to move more air with the new DC furnace motor ?I know moving them up the wall to ceiling level would help but how much should it change. If the furnace keeps the house more comfortable in winter shouldn't the blower improve the ac function in the summer as well?

 

[Chemist1961]

Stat says it's now only 68 outside, so I guess we'll cool with the breeze for an hour or two , then close up again.