China Best Efficiency Vacuum tube Solar Collector 1. EN12975, Solar key mark,SRCC,CE,ISO. 2. 0.68~0.73 premium conversion Vacuum tube solar collectors -- Keymark/EN-12975,SRCC,ISO,CE,CCC Feature: Working principle1) When the discrepant temperature of the solar collector and water tank reaches the set value, the controller shall start the circulation pump automatically.2) The circulation pump ...