Dennis,
Almost. Power should go to 30, not 87a. 87a is unused. And yes, the other fan wire goes to ground.
If your existing switch completes the circuit to ground, then 85 should go to one terminal on the switch. Connect power to 86 (as well as 30).
Or you could rewire your switch so that power goes to one switch terminal and the other switch terminal goes to 86 on the relay.
John
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