The outside shell of Nigel's HX design is PVC type pipe. I think my HX will only run at
30 to 50 PSI on the water side. But, if case of a pressure regulator failure, it could go up to 90 PSI.
So, I'm a little reluctant to use the PVC design.
However, it's only water and it's loss wouldn't be a big deal..
I wonder how important the ID of the refrigerant tubing is.?.
Because, since I have a lot of room to work in,
I could use large ID PVC and build a much larger
version of the Nigel MK2 EX. Both fatter and longer.
That way, I could use standard 1/2" copper pipe and fittings, for the refrigerant. Makes building it easier. (If I have a very hot torch).
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I've noticed that many of the flat-plate EX units on Ebay have a max pressure limit of 435 PSI..
That kinda makes me wonder about using R410A, with it's high pressure.
Have you seen any that are rated to 800 PSI??