A flow meter is used to measure the flow of heat transfer fluid.  Most systems operate at 1-1.5 gallons per minute per collector.

Older systems used a thermometer which has been replaced by a LCD display on new systems.  A differential thermostat measures the difference in temperature between the collector and tank.  Sensors and a pump control manage the function of the system.  When the difference in temperature exceeds 15 degrees F the pump will turn on to circulate the fluid. 

A thermostatic mixing valve combines hot and cold water to set mixed water temperature to fixtures.

Circulating pumps move liquid through the system.  They are AC or DC powered.  They are made from iron, bronze or stainless steel. 

Solar PV pumps use a side bar panel for a direct drive current limited system.  The system only runs when the sun is available to the PV module.  This is a simple and elegant system where the heat and power are well matched.  This system should have a controller to prevent overheating. 

Pump Stations are programmable units with a digital readout that allow you to customize your system settings.