rework closed loop to drainback

catbird

currently have closed loop system with 5 4'x8' collectors fed by hartell solar coupled pump. need best pump option for 8' head, solar driven if possible, in drainback setup.

SWEI

8 feet of head

is right on the edge for a Laing Thermotech D5 http://documentlibrary.xylemappliedwater.com/wp-content/blogs.dir/22/files/2012/07/BR-20A.pdf

hot_rod

Lower the lift head

By raising the drainback tank as high as possible Those DC solar pumps are not available in a wide selection

matt_sunwaysolar

marchpump.com

March Pump has some of the highest head ratings that I have seen in 12V and 24V powered pumps. I believe the 809-HS model has the most appropriate capabilities.



It is probably true the most important thing can do is to decrease the height that fluid has travel vertically.



With 8' of head at 5gpm, you can run an 115V circulator at about 80 watts max. (Less if you use a variable speed controller.) Something like the grundfos up15-58fc.

hot_rod

ECM circs

are another option if you have 120V. Maybe pump that system with17W on the Alpha.



On dual pump, high lift head, drain back I have paired and Alpha with a 15-58. Start the siphon with both running and drop back to the Alpha at speed 1 or 2.