at what thermostat setting?......what are your usual run times for your AC.?...high summertime humidity location?

TD

tstat set at 79. If it is low to mid 80's it runs for 15-20 minutes. upper 80's to low 90's it will run 25-35 minutes. It was in the mid 90's a few days ago and it was running 40-45 minutes a couple of cycles. The unit is a little oversized I think, but that is just a guess. The 27 TD is from the return coming from the attic so the attic is heating that air up. I have another return that goes directly from the house to under the air handler, that air is at room temperature and if I use that that TD is more like 21.

I would monitor once summer hits especially inside humidity. I think your thermostat setting is unusually high.

TD

I don’t disagree on the setting but 78 was a little chilly so we’re right between the two. when measuring the delta T should I use an average of the two returns since one is getting heated coming through the attic and picking up heat? Or should I just use the return that goes straight into the air handler which is basically room temperature?

If you have a central return (s) in the living area preferably in an inside hallway not near a window or any heated device, that is where I like to take the return reading. Take your supple temp in different inside locations and then use an average.

IMO