Understanding

[nh3wizard]

Just as the says: air on at a certain temperature and air off at a certain temperature.
You want an area to be 40 degrees, so you might want the unit to turn on at 42+ degrees and turn off at 38 degrees, just an example

[TRASH101]

air on = condition of air before being conditioned
air off = condition of air after conditioning

[sinewave]

Just as the says: air on at a certain temperature and air off at a certain temperature.
You want an area to be 40 degrees, so you might want the unit to turn on at 42+ degrees and turn off at 38 degrees, just an example

I'm with Trash!

[nh3wizard]

I'm with Trash!

Why so confused? I guess it all really depends on what kind of system you are working and the controls they use. This is why I think its sometimes better just to keep my mouth shut.