Most efficient way to run Mini Split ACs
I’m currently cooling ~1900 sq feet home, 2 floor Colonial zone 5, with an AOU24RLXFZ hooked up to a 12K wallmount @ top of open stairway, and a 7K in the master BR which is 1/2 of the second floor. I’m very impressed with the cooling abilities so far as Boston has seen some days close to 90. I keep the stairway unit at 71 (1 degree offset in function settings), and BR is at 72 in economy mode, but on low fan so it is always running quietly (fan makes annoying ticking noise in auto fan mode). Entire home +/- 1.5 degrees of 71.
With days in the 80s, the condenser has been cycling about 6.5 minutes on, 1.5 min off. I also have another 12K attached to a second AOU24RLXFZ that can serve the entire open first floor if needed (used more for heating), as well as a 12k in a finished attic room.
My question is are there any efficiency gains to be had by running the second condenser for the first floor, for either humidity control or for keeping the second floor unit more in the sweet spot of modulation? These units aren’t the most efficient and I would certainly change some things if I did it over again.
Any reason to keep the second floor unit on low fan vs auto? I will say it doesn’t seem like the unit has to try very hard, it’s not like it’s blasting on full fan trying to cool the house down, although we’ll see how this set up does for a week in the 90s.
House has updated windows, sprayfoam in attic and large shady oak trees. I had come up with 30k BTU load on coolcalc but I’ve read that can be up to 30% high.
At roughly 1200 sqft per ton that seems pretty ambitious for this to continue on throughout the summer, but was curious if anyone had any insights.
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