I received a call today from Rich Baker in Massachusetts who is working on a crippled cricket. It has an estimated 40′ run between the collector and the heat exchanger, and the solar pad / solar tank has been replaced with an electric water heater with an internal heat exchanger. He said the system worked for a few days, but then quit. What really amazed me is that they were able to swap out the heat exchanger without draining the solar side and evacuating the system at the collector because there were valves on the solar loop that isolated the heat-exchanger from the solar loop. At first I shuddered. You can put a valve in this evacuated system. Every time we tried the valve leaked. But then I realized that with at least 35′ of fluid above the valves, the valves are never under a vacuum, they are most likely under pressure, so even if they leak, no air will enter the system other than air that might dissolve into fluid exposed at a leak. So, why not install valves down by the tank on really tall systems? How about 3-way valves that could direct heat to something else, like a second tank, a cooling fin for overheat protection, a kitty litter heater, etc.
Thanks for the call Rich. Good luck getting this system back on lin