I have a 2000 hot spring spa. w/the IQ200 control unit.
have had no problems for 8 years, I changed the water yesterday and turn on.
the next day i check water temp. and it was still cold...
I found the gfici 30 amp had tripped. would not reset.
check power ok, heat had no shorts.
Just messing around checking things, I removed the aluimum cover for holding the plastic cover and the heater works. I put the steel screw back in the the holder and in trips.
done this 10 times and same results.
the only thing I sae was a lot of condensation becase the water cas cold, heater housing was
wet and small amount of water on floor of pump and control area.

The 30 amp breaker only runs the heater, so we know it's in that circuit. Unhook the heater wires on the IQ2000 - far left wires, see if the 30 still trips.
There could be moisture on the circuit board. This would trip a GFI.
Check the 3 wires that go from the left circuit board (terminal board) to the main circuit board (red, blk & white). Make sure the wires are Ok and not nicked.

Keep us posted

Pete
http://www.makesmeshutter.com