I am trying to hook up a thermostat to my attic ventilation fan. There is an on/off switch already there. When I have everything wired as the thermostat says to the fan runs all the time and within a few minutes trips the circuit. When I bypass the thermostat and just use the switch the fan runs and does not trip the circuit. Any suggestions?

If thermostat has 2 wires, disconnect wire from switch that goes to fan.
Thermostat connects to these 2 points(switch and wire removed from switch).

Sounds like it's tripping when the thermostat kicks in. It's not wired correctly. It's probably wired across the neutral.