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First, I must admit I needed to look up Coanda effect :o). Always something new to learn.
So, based on what your saying and what I am observing, it seems my suspicions were correct. Setback is not worth it when less than a certain number of hours. 9 hours not being enough. Similar to what I said, lately I have been holding one temp indefinitely and it goes without saying the house is comfortable upon return home. But the temperature is also more stable because not only is the pocket of air in the house cool but the mass of the interior is too. And by default there is no recovery or pull down.
Sorry if I wasnt clear. When I said 'swelling' in my first post I meant (in other words) heat entrapment in the house after a hot day, not humidity. When the air comes on there is a cool pocket of air inside the house but the walls, etc are warm from direct sunlight.
At any rate, the paralell humidistat concept is very interesting. Yes, Hi-V removes more humidity but there are times when the temp is at set point but the humidity is a little too high and its a little uncomfortable. There are times I wish the system would come on just shortly to 'wring out' the interior air a little. A paralell humidistat would do that, correct?