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No complaints or questions just an observation.
My SHW system circulates with a March DC pump hooked to a well worn 60 watts Siemens PV panel. It is wired direct through a DC controller that runs the pump as long the panel is putting out enough power and the temp at the outlet of the hot water panels is higher then the storage tank temp. It came with a 20 watt panel originally but was soon upgraded to the Siemens panel that is definitely not aging well (brown tinged coating with some delamination near the grid wires) but still seems to do the job. Even with the larger panel I still get in the situation where the glycol in the pipes in my unheated attic is cold enough that the viscosity has increased the friction loss up enough that the DC pump will not circulate the loop. Its was -7F last night and is now about 3 F and when I went by the pump it was merrily spinning but definitely no flow. Its been this way for years despite my messing around with the concentration. It doesn't seem to hurt the pump as its been pumping for 15 years this way. All it does is heats up the piping downstream of the pump until the temps get high enough for the glycol to start flowing. Its the original glycol and the pH tests fine every couple of years so I just let it run. They are regular flat panels so at best I get 80 degree F rise over ambient so all I do in the winter is use it for preheat on the incoming well water. I have an Amtrol indirect water heater that I charge up with my wood boiler downstream. I switch it over to supply the house direct for about 8 months a year.
Given that flat plate SHW panels are pretty well a dying technology replaced by heat pump hot water heaters and a few extra PV panels on a grid tied array, my plan is let the system run until I need to spend a lot of money on it. In 15 years the only parts is a new check valve and an expansion tank that lost a bladder.
My SHW system circulates with a March DC pump hooked to a well worn 60 watts Siemens PV panel. It is wired direct through a DC controller that runs the pump as long the panel is putting out enough power and the temp at the outlet of the hot water panels is higher then the storage tank temp. It came with a 20 watt panel originally but was soon upgraded to the Siemens panel that is definitely not aging well (brown tinged coating with some delamination near the grid wires) but still seems to do the job. Even with the larger panel I still get in the situation where the glycol in the pipes in my unheated attic is cold enough that the viscosity has increased the friction loss up enough that the DC pump will not circulate the loop. Its was -7F last night and is now about 3 F and when I went by the pump it was merrily spinning but definitely no flow. Its been this way for years despite my messing around with the concentration. It doesn't seem to hurt the pump as its been pumping for 15 years this way. All it does is heats up the piping downstream of the pump until the temps get high enough for the glycol to start flowing. Its the original glycol and the pH tests fine every couple of years so I just let it run. They are regular flat panels so at best I get 80 degree F rise over ambient so all I do in the winter is use it for preheat on the incoming well water. I have an Amtrol indirect water heater that I charge up with my wood boiler downstream. I switch it over to supply the house direct for about 8 months a year.
Given that flat plate SHW panels are pretty well a dying technology replaced by heat pump hot water heaters and a few extra PV panels on a grid tied array, my plan is let the system run until I need to spend a lot of money on it. In 15 years the only parts is a new check valve and an expansion tank that lost a bladder.