... operated completely automatic if connect with intelligent controller. Non-pressurized Solar heater:Features: 1) Can be operated completely ... tube: 1,800mm / Φ58, 15pcs/set, 20pcs/set or 30pcs/set3) Tank: 150L, 200L, 300L4) Collector housing: 0.8mm stainless steel ... , frame 1.5mm stainless steel, insulation material, rock wool or polyurethane5) ...