Thought about this issue a bit more. The hartford loop is installed in the side of the spa. The distance from the top of the water to the top of the spa is 3". Take away 2" for the size of the pipe and we end up with a hartford loop that is a maximum of 1" above the water line. There is no check valve so what is happening is that when the spa turns off, the sudden lack of pressure in the blower pipe is causing water to flow back into the water pipe. This in turn causes at least a partial blockage when the blower is turned on because the blower is unable to push ALL of the water out of the pipe (it's about 2.5' under the water level in the ground). Because of the partial blockage the blower is overheating because it cannot blow the amount of air required to keep cool.
I believe this explains why the previous blowers melted the pipe. The newest blower detects that it's overheating and shuts itself off, therefore it doesn't melt the pipe. My guess is that it ran for roughly five minutes before shutting down. The base of the blower was around 95 degrees on a day when the outside temperature was 55 degrees. I would think that if things were working perfectly that the temperature of the pipe would be well below the 40 degree difference.
This also explains why the blower is requiring twice the amperage specified in the documentation.
I have reached out to the supervisor who built our pool. He is very knowledgeable and hopefully he can get this fixed for us. The only option I see at this point is to raise the sides of the spa by the required 11", fix the hartford valve, and redo the travertine and glass tiles. Any alternatives???
Also, if they raise the sides of the spa, how should they go about doing that. Should they add rebar, shoot additional gunnite and then seal that section with Aquaron???
Is there a minimum distance we should have between the bottom of the 180 degree 2" pipe and the water level in the spa to prevent this issue?
Thanks in advance.