[Servicetech]

Have you considered using a standard HVAC contactor and a delay on break timer? Seems like it would be a lot simpler and cost less to build. 4 parts total:
1: 24vac transformer
2: Delay on break timer (most are either 3 or 5 minutes fixed)
3: Standard HVAC contactor
4: Current switch (same as you are now using to break connection above certain amperage, you would use the NC contacts instead). You could also use a standard HVAC hard start relay if you could find one with the amperage you required.