Forced Flow System

In forced circulation systems, two pumps in tandem are used for circulation of water between collector bank & system insulated tank. The pump operation is controlled by OTC (Differential Temperature Controller), which is fitted Inside the Control panel. OTC senses the cold & hot water temperature through two sensors, one fitted at the bottom of the tank to sense cold water temperature & the other fitted at the top of the last collector of the row in the collector bank, to sense the hot water temperature inside the collector
The difference in temperature between the two sensor points is the criteria for the operation of the pump that is controlled through DTC. This temperature difference can be set between 0 to 10 deg, C.
Solar radiation falling on the collector heats up the water inside the absorber. The temperature of water starts gradually increasing compared to the water temperature inside the tank. When this temperature difference between the sensor points reaches the preset temperature difference in DTC, the pump is switched "ON". This will result in entry of cold-water form the system-insulated tank into the collector bank & discharge of hot water from the collector bank to the system insulated tank.
The sensor fitted at the collector will sense the temperature of cold water entering into the collector & puts "OFF" the pump when this temperature difference between the sensor points falls below the preset temperature difference in DTC.
The process of switching ON & QFF of the pump & circulation of water continues till the end of the day. By the end of the day, the entire quantity of water in the tank reaches the system-designed temperature, provided the radiation level is at minimum of 800 watts per sq.mtr.