I just installed a '95 Cal Spa Deluxe Model CP-12N. We have it wired with a 50amp breakers at our house electrical panel, going with 6gauge 6/3 wire to a 60amp non fused disconnect 10 ft. from tub, then wiring to the tub. The tub has an internal GFCI breaker built in.

I started it up for the first time last night, watched it warm the water up for a couple hours then headed off to bed. This morning got up to check it and the GFCI had been reset. The water was approx 85* I reset the GFCI and it ran for about 10 minutes before flipping again. I then played with the settings and came up with this: Whenever the heater turns on the GFCI Flips.

These are the diagnostics I have ran:
Check all electrical connections from panel to tub to make sure everything was tight
Removed control board cover (with power off) and check for any loose connections
Tested OHMS between lugs on element (read 13 - 13.5)
Removed wires going to lugs, turned on tub heat and the "Heat On" light comes on and seems to run normal

*Note* when looking at two lugs going into element it looks like they are covered with a lot of brown, rusty looking corrosion.

From the information, does it sound like I need a new element, electric assemble, or ????

Thanks you! Let me know if you require pictures or more information.

i think it's time for a new elemnet

Is http://spapartsnet.com/Electric-Heaters-Parts/Heater-Elements/55NINS_476_0_1.html the correct one? After reading the description of it Im still not sure to go with the 4500 or 5500.

The smaller of the two will be better for the contactors that run it. The 5500 will heat faster, but will destroy your contactors faster. I always replace with the smaller... since the time it takes to heat isn't all that much slower. I'd rather not burn up components just to save a few minutes with the larger heater.

Thanks charger, Ill be ordering one up today!