Originally Posted by krazydave
Just to chime in, I built a two tap jockey box using a four pass cold plate. Each tap goes through two passes on the plate.
I too have read everywhere that the cold plate should be elevated and drain left open to keep it out of standing water.
Not once have I done that.
I've never put much stock in the old 'never let the cold plate sit in contact with water' theory. It gets bandied about all the time, but never have I seen any science to back it up. It keeps getting repeated, but I've not been able to find an acceptable reason as to why.
The physics of the problem even seem to be quite the contrary - water is at it's densest just a bit over freezing at 4 deg C (~39F). This means that as the ice melts, the coldest water will then sink to the bottom, leaving the slightly warmer water in contact with the ice. Now - we are dealing with a very small scale, so the actual differences are probably negligible and thermal convection likely not significant.
However, as far as I can figure - as long as your ice/water mixture is kept at the serving temperature you want your beer at, the most efficient cooling will be with a mixture of ice and water as the water is a far more efficient cooling medium than just ice and air.
I've got a 3 tap jockey box with two cold plates -a single pass and a double pass. I've used it for hours on 80+ degree days with no issues without draining off the water. I do tend to set the pressure up to 20-25 psi to compensate for the temperature difference of the kegs, but even then I get a nice pour all day after the first glass or two from each line.