After reading several of the other postes I did some trouble shooting on our tub. Fist: when the tub comes on to maintain heat or start the programed cycle, the GFI trips in about 5+ seconds. Second: if I disconnect the heater wires from the sloidstate relay inside the controller, the GFI won't trip. Third: if I leave the heater wires connected and disconnect the pressure switch wires(at the switch), the GFI won't trip. This is where I need to know..........bad pressure switch, bad heater, or? The heater is a Brett model #20-00319 ba, 5.5kw 240v. Our tub is a AmeriSpa from the mid '90's

Sounds like a bad heater...it doesn't trip when the pressure switch is disconnected because the P-switch is before the heater in the circuit and if it is not connected it will not allow the heater to come on, and therefore the GFCI will not trip.

Thanks for the feedback Dan. I bought a heater from Spa Parts and that did the trick. The port for the pressure switch was in a different location so I had to do some minor mods but everything is woking now.