Okay, time for a bit of an update. I haven't figured much out yet, but I'll tell you what I do know. I told you that the heating element was replaced and, while that stopped the GFCI from tripping, the relay on the circuit board is still popping open which breaks the circuit and won't allow the heating element to run. Well, after reading a fair amount and getting suggestions from a few people on these forum sites, I decided to see if the pressure switch was bad. I was sure that I didn't have an air lock situation, but it would've been logical to assume that a bad pressure switch would think that I had no water flow, which would cause the relay to trip. So, I went and got another pressure switch and installed it. That didn't change a damned thing. The situation was identical to what was going on before.
I called Great Lakes to see what they had to say. I told them that I'd changed the element and tried a different pressure switch. I also told them that I'd heard about the high-limit switch, but couldn't locate it. Apparently, when your tub overheats, it will trip the high-limit switch, and, on many of them, you must manually reset the switch. Well, they told me that the high-limit switch on my tub is not one that requires you to manually reset it. Oh, and I still don't know where in the hell that switch is.
There was a suggestion about the possibility that I over-tightened the heating element, which can crack it and cause a ground fault. If I'm not mistaken, wasn't it a ground fault that I had that was tripping the GFCI switch? The GFCI is no longer tripping. The only thing that's happening is that about 20 seconds after powering up the tub, the relay on the circuit board that controls the heating element is popping open and breaking the circuit. It tries to run the heater, but eventually gives up and shuts it down. If I'd messed up the heating element and was getting a ground fault, wouldn't it still trip the GFCI and not just the relay on the circuit board?
Oh, one more thing: my tub is a Manitou by Great Lakes Spas. It was purchased in 2000, and apparently was the last of its kind, meaning that it was made to run on 110 or 220 with only minimal conversion. By that, I mean that neither the heater nor the pump needed to be changed for the conversion to work. The next time Great Lakes made that tub, it was 220 only. I don't know all of this stuff as gospel. I just know that this was the information I got from the dealer when I bought it. I guess that they could be wrong about that.
Here are a few more facts that might help. The tub ran for years on 110 power with no problems. It gets stored every summer. We empty it out and put it away. The last time it was emptied, it overheated. It had not been run at all since the OH error code showed up. When we powered it up, it showed no error code. The temperature read-out was correct and the LED was on, showing that the spa side control was calling for heat. The pump is working fine and all the jets are kicking ass. Just got no heat!!
Thanks for all of your help.
Jon
P.S. Oh, one more question: somebody said that there are seperate pumps that run the jets and the water flow through the heater. Something about a circulation pump? Can anyone elaborate on that? I don't think this is the issue, though. I'm pretty sure that the water is passing by the non-working heating element and out the big hole to the right of the captain's chair.