Hi.. I have a 3-4 yr old Freeflow spa with a Balboa spa pack (M7) & 4kw heater, hooked up to 120v. Worked great until about 2 weeks ago then started blowing the GFI frequently. Decided the wiring out to the spa outlet/plug was old anyway, so rewired tested.. still blew the GFI. Removed the filter (orderd new & replaced) and removed the GFI from the cord/plug. and put a new GFI breaker in the breaker box. (nothing else on this circuit/breaker). Disconnected heater element copper tabs and checked across terminals (14 ohms) and each terminal to ground (no short indicated).. and plugged it back in... seemed fine and heating water, but noticed this morning it blew the GFI again. Reset it, and waited (since it was near the setting I set of 103). When it reached 103 the low pump remained on along with the heater light (since it's 120 it only heats on low pump), and then gave a HH error (overheat 118 degress at heater error).
Great forum and very helpfull, but should I be looking for a flow issue (seems fine) scale on the element? Temp sensor issue? or ???? I'm a bit lost at this point.

If this info helps, Noticed when I first plug it in now it says "12" (no idea) then Pr (for self test?) then "--" (until it finds temp?) The "--" never was on before or if so for a very short time... now it seems to stay on. My wild guess it that it doesn't know the correct temp (bad sensor? which one? where?) and just starts heating when I reset the GFI until it overheats again and breaks the GFI again?
Thanks in advance for any help or recommendations!
Marc

You need to approach this one problem at a time - First gfci issue. Replace the heater element. You can test the element correctly by measuring in the meg-ohms range any terminal to ground. Second - You may or may not have an issue with the sensors and or board. But I'd do the cheap thing first and replace the element. If your element sheath/insulation internally is compromised the the water inside the heater is literally electrified with 115 volts - and guess what is on either side of the element? The sensors. Regardless of insulation characteristics, those sensors are not grounded and are connected directly to cmos devices on the circuit board and this could lead to unpredictable operation. http://spapartsnet.com/Spa-Parts-On-Sale The 4500 should work fine.

I sure appreciate your input and thanks for your prompt reply.
I disconnected the heater copper tabs from the element (didn't remove the heater tube or element obviously). The readimg from terminal to terminal on the element was about 14 ohms. Checked each terminal to the tube/case for ground and inidicated zero continuity. Those readings along with the fact that it is heating the water, I just assumed the element was ok. I'll order another element as thats a cheap fix, and if nothing else a spare on hand can't hurt, but if it was bad wouldn't it show a ground or incorrect resistance? I didn't check the amperage draw. Do you need to remove the element to really check completely/correctly?
Thanks
-Marc

No you don't need to actually measure amperage draw - although it is the best method.

Amperage draw can be calculated by Voltage at terminals divided by Resistance.

Regarding measuring for a ground fault though, the element needs to be in the case, with water in it. (preferably near as possible to the time the gfci tripped). You're looking for a measurement that's anywhere from 100k to 2-3 megohms. Not a continuity check. If you get something in that range then your element has been compromised and it's leaking voltage into the water.

Ok... replaced the heater element. don't think old one was bad, but better safe than sorry. GFI still trips. Removed/unplugged everything connected (ozone, light, heater, etc) and still trips immediately (sometimes after a few minutes randomly) when low or high pump motor starts. Tried running extension cord to different GFI in the house... GFI didn't trip... everything worked fine, spa heated to 102. Seemed like a wiring or GFI issue to me so swapped out the GFI's (put the one inside outside, and visa versa). Still trips at outside GFI and works with extension cord on inside GFI. Wiring to outside was old so decided to run all new cable from breaker box... all new wire, breaker to spa outside and GFI recepticle. (120v spa connection) Black to standard 20 amp breaker, white to neutral (bonded at main breaker box to neutral) and ground all ok. Still same issues.
Could the motor or condensor in the motor cause the GFI to trip? Obviously there is a voltage drop when using the extension cord... maybe with a bit lower voltage the problem doesn't occur? Motor does seem to get hot (enough to where I couldn't leave my hand on it for an extended time) and I can see blue flash through motor vent hole when it switches on or to high speed.
Sorry so long but getting a bit frustrated. Couldn't find specifics for checking motor/condensor for fault. any advice?
Thanks