I have the ASI spa controller in the pic on the following link:
http://www.spa-pack.com/stainlesspack.htm

I originally thought based on the post I have read that I may have a bad heating element.

When the heat control is set to thermostat, the GFI circuit breaker blows as soon as I turn the heat dial on (clockwise).

However, if you set the spa controller to clock, the heater comes on fine and works properly. Any idea of what could be causing the trip.

Is this a new or used spa pack? Have you previously had this running in the past? Have you replaced or changed any component of the system at the time of failure?

Amazing how people ask very detailed questions but yet never come back to check on the answers.

New policies are going into effect soon.