The Goldline GL-30 differential control provides maximum operating efficiency and flexibility for solar thermal systems. It handles most differential temperature control functions for space or water heating. Output operates a circulator or fan when sensing an appropriate temperature differential. Adjustable differential, from 8° to 24°F, allows the GL-30 to be tailored to specific needs of the system.Storage high limit, adjustable from 110° to 230°F, protects most solar storage systems. Recirculation capable and numerous other options available. Relay rated at 10 amps output.
Goldline Liquid Controller GL30 
The Goldline GL-30 differential control provides maximum operating efficiency and flexibility for solar thermal systems. It handles most differential temperature control functions for space or water heating. Output operates a circulator or fan when sensing an appropriate temperature differential. Adjustable differential, from 8° to 24°F, allows the GL-30 to be tailored to specific needs of the system.Storage high limit, adjustable from 110° to 230°F, protects most solar storage systems. Recirculation capable and numerous other options available. Relay rated at 10 amps output.