It isn't a separate fan, but rather the blower on the central air / heat unit. This is what I came up with and seems to work ok.
If
Control '14.21.07 - Heat Control' is switched Off
Or Control '14.21.07 - Cool Control' is switched Off
Then
Wait 1 minute
Set '14.21.07 - Main' Fan On
Send Notification to 'Default' content 'Fan On'
Wait 15 minutes
Set '14.21.07 - Main' Fan Auto
Send Notification to 'Default' content 'Fan Off'
Else
- No Actions - (To add one, press 'Action')
Looks to be working ok for now.
Thanks,
Shawn