I have a 1993 Leisure Bay Spa, St. Thomas model. I bought it used and had to replace the heater element and a couple cracked PVC fittings. I wired the spa 220V but it had never been wired that way before. Everything seems to be functioning properly. The 24/7 circulation pump is on and pumping fine. The heater works and heats water to proper temperature, and the single speed jet pump also works fine. The only problem that I am having is that the high limit switch is tripping frequently. I had the switch tested and it tripped at 114degrees. I also stuck a thermometer in the hole for the switch probe and verified that it did indeed get that hot.

1. There is flow
2. The filter is brand new
3. The high limit switch is good
4. The heater element is not touching the sides of the heater housing

Any ideas would be much appreciated, I'm just about out. My next step is to take apart the circulation pump and make sure that it is not clogged up with anything. But I really don't think it is. It has designated jets for this pump and it puts out water fine. I'm going insane.

Is there anyway that the heater could be too hot when running 220V for this system? Will it run slightly cooler if I hook it up 110V instead?

If your high limit t-stat is tripping at 114, that seems a bit low, most trip at 120 degrees. Secondly, yes 220 is going to produce more heat, 5.5kw vs. 1.5kw for 110 volt. The water should be moving through the heater fast enough to dissipate the heat, if there is a heat build-up in the heater that is bad. When the heater is operating the heater should be a bit warm to the touch, if it is hot, then you are not moving water through the heater at a high enough rate.

Is the tub getting above the 114 trip temp? If so the high limit is doing it's job, I suspect not, so it is a reduction in flow thru the heater since you replaced the filter element already.

Thanks Jeffz for your reply. I guess the first thing I should do then is get an accurate reading for what temperature the High Limit is tripping at. I've been told that anywhere between about 114 and 120 is normal. But maybe I need to make sure it's letting me get to 120, that could be the whole problem.

Like I said, the previous owner never wired it 220V, so they never experienced this problem - for reasons you said below, they only had 1.5Kw of heat. Maybe it really is just a high limit sensor issue.

Can I ask u one more thing. I have to purge air pretty regularly from my air filter lid. How often is normal for air to build up inside here? Is it safe to say that if I have to do it pretty much every time I use the spa that there is a suction leak somewhere?

It is not normal to have to purge air, you need to find the leak on the suctions side of your plumbing.