copper tubing for a heat exhanger for indoor pool AC

[Akshay]

Hi All

The problem with indoor pools is the moisture especially in the winter, I have a 3 ton central AC unit but it does not make sense to waste the heat outside through the condenser. I have been shopping for a pool water heat exchanger for freon. I have not found although I am sure they are out there. I have decided to build my own from 5 inch PVC pipe with a the freon piped through a coil of copper tubing inside the sealed 5 inch PVC pipe which will have 1 1/2 inch inlet and out put connections to the pool pump post filter. I am sure I can seal the holes for the copper tubing very well with silicone.

My question is will the copper tubing survive the pool water?

[chem geek]

You should first make sure that the temperature of the output coils is going to be hotter than the pool water temperature. It's clearly going to be warmer than the air temperature, but if you keep your pool warm there may not be enough of a temperature difference for efficient heat transfer.

As for corrosion with pool water, if the pool is a non-salt pool (doesn't have a saltwater chlorine generator, SWG, nor elevated salt levels for any other reason), then use of copper could be OK as this was typically done in gas heaters for years. However, you should use Cyanuric Acid (CYA) in the water at a low level such as 20 ppm with 3-4 ppm Free Chlorine (FC). Without the CYA, the "active" chlorine level (hypochlorous acid) will be too high and may corrode the copper, especially if you do any shocking.

To be extra safe, you could use either titanium or a cupro-nickel alloy as is more commonly found in modern gas heaters. That would resist corrosion even in saltwater pools.

Richard