... the vacuum tube,therefore no water in the tube,each tube can work alone,so the solar colletcor can work even ... 50 degreeCapacity 100L 150L 200L 240L 250L 300LCertification: SABS,CE,Solar Keymark, SRCC,ISO9001:2000Parameter Table-1 Place of originalChinaModel ... :diameter(mm)360/460Vent connection(inch):1/2Electrical heating connection(mm):47Water connection(mm):1/2,3/4 compact pressure solar hot water