Solar controllers regulate the pump that moves heating liquid through a solar hot water system. They vary in complexity and include temperature sensing ports and output ports. Solar water heating systems consist of a collector and a water tank, with fluid movement controlled by an electric pump driven by a solar controller. More sophisticated controllers include microprocessors and digital displays for improved efficiency and system information. Solar water heating is growing in popularity due to rising energy costs.
In terms of solar hot water systems, a solar controller is the component that controls the pump that moves the heating liquid through the collector. Solar controllers differ in sophistication and functionality, but all include at least two temperature sensing ports and an output port that drives the pump. More complex controllers may include additional electronic features that improve system efficiency or digital readouts that display important system information. Depending on the range of functions included, a solar controller can be included in the heating system itself or in a remote location accessible to the user.
Solar water heating is steadily growing in popularity around the world due to soaring energy costs. These systems usually consist of a collector and a water tank. Water, or a specially formulated heat transfer fluid (HTF), is exposed to solar radiation across the large surface area of the collector. The heated fluid is then circulated in various ways in the water tank where it transfers heat to the contents of the tank. Obviously this movement of fluid between the collector and the water tank is essential for the efficient operation of the hot water system, but it also serves as a safety measure to ensure that the collector does not overheat in times of low demand.
In active solar hot water systems, this fluid movement is achieved with an electric pump driven by a solar controller. The controller has several temperature sensing ports that collect data from temperature probes located at various points in the system, most notably the manifold and tank. When fluid circulation is required, the controller will send a signal through an output port to activate a relay which in turn turns on the pump. When system temperatures reach the point where circulation is no longer needed, the controller cuts power to the relay, shutting down the pump again.
This basic functionality can be achieved with very simple electronic circuits which are often integrated into the manifold or motor housings. However, many solar control units have additional functionality in the form of additional sensors and controls to prevent wasted energy due to short cycling of the pump. This level of control is usually achieved by including microprocessors in the controller circuit. This type of controller is typically located where it is easy to access and often includes a digital display that can provide essential system information. Many solar controller models also include override controls to manually start and stop the pump.
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