Apex Programming for ATO

Fallback is the state the outlet returns to after losing power, or losing connection with the APEX. There will be a time when the APEX is loading that the outlets are not being controlled, so they will be in the fallback state.
Set is the normal state you want the outlets to be in during operation. Pumps are usually set on, and code added to turn them off. Heaters are usually set off and code added to turn them on.
Are you setting it up with float switches via a breakout box, or what type of ATO are you running through the APEX? The coding will be a little different depending on what and how you are running the top off.
I'm no expert so I would get a second opinion. You would have to have the statements to turn the ATO on when needed, but this would not run it when the skimmer is off and delay it turning back on for 1 minute.
Fallback OFF - In the event of a loss of communication you would want the outlet to remain off
Set OFF - During normal operation the outlet would be off.
If Outlet Skimmer = OFF Then OFF - Checks the skimmer outlet and will not turn on the ATO if the Skimmer is off.
Defer 001:00 Then ON - Will delay 1 minute after the skimmer comes on before allowing the ATO to turn on again.

 

I think most people doing an ATO with the APEX use a float switch hooked up through a breakout box. Then the code would include a command to turn the ATO on as needed.
Fallback OFF
Set OFF
If switch1 Closed then ON
something like that.
Since you're just wanting to power a "standalone" ATO using that outlet putting the Set ON should work just fine followed by the rest of the commands that turn the outlet off while the skimmer is off. The only thing you would want to watch for is if the ATO does anything weird after losing power. I am not familiar with the Tunze ATO. Also the code I posted will leave the ATO off anytime the skimmer is off. If you go without the skimmer for an extended period of time you would have to change you code around.

 

You might be able to do something with a virtual outlet and set it up to only run so many minutes per hour, or any time period for that matter. Basically it would look for the virtual outlet - which would only satisfy the statement and allow the ATO to run during certain time periods. I haven't done much more than read up on virtual outlets so I've got no firsthand experience. But from what i've seen they can be a very powerful tool that allow much more from the apex.