Question about automating evacuated solar heater

[wayner]

Split by moderator from HERE. jblizzle

Does someone have more info on how these automated controllers work? I have an evacuated tube system in Toronto and just have a manual valve that stays open. But with tubes you can't close and open if the sun is up since that will fracture the tubes. So is this even an option for me?

 

[pooldv]

I am not familiar with evacuated tube solar panels. But, if you use a regular 3 way valve, instead of a solar 3 way valve, the panels will not drain down when the valve closes. The solar 3 way valve has a pin hole that allows the solar panels to drain when the valve is closed. When I first installed my panels I used a regular 3 way valve and the panels stayed full when the valve was closed.

The solar controllers have a temp sensor in the water line at the equipment pad and a temp sensor on the roof. When the temperature differential is met and the solar temp is higher than the water temp the controller will open the solar valve. Mine also ramps the pump speed up to the preset for solar which is 1950 rpm. The controller will close the valve when either the water temp reaches the target temp or the solar temp drops down to the water temp.