[vmike]

Surprisingly, the failures are almost always on the freon loop. Generally a pin hole or split next to the joint where the tubes bond together. Heat, I assume exacerbated a fault in the tubing itself. I have also seen a similar fault in the cooling tubing. But remember, we use them for research applications here, so they're not always well treated or operated within factory specifications. The ones I use myself are all used purchased at surplus auctions and removed from salvage equipment. I have three in operation that have never caused a problem.

If I were to attempt to make one of these myself I'd snake a smaller tube through a larger one and roll it up. I have seen a successful homemade one however in a friends automated beer brewing system. He laid the two tubes side by side flat on a table, soldered them every foot or so, smeared them up with heat transfer compound and wrapped them in some rubbery tape of some kind. He then rolled it up and stuck it in a 5 gallon steel bucket and filled it with foam. The tubing was simply rolled around a piece of sonotube and zip tied together. Seems to work.