Solar Water Heating Pump Controller

A solar water heating pump controller is a key component in most solar water heating systems (DIY or otherwise). The controller is there to turn the pump on when the fluid in the solar panel is hotter than the water in the hot water tank (or swimming pool), and keep it turned off at all other times. First of all, it is worth noting that there are
Solar Water Heating Pump Controller - schematic

solar hot water system designs for which a controller is not required. The most common is Thermosyphon Solar Water Heating in which the natural rising of hot water (and sinking of cold water) is used to circulate hot water from the panel to the hot water tank, and cold water from the bottom of the hot water tank back around to the panel. It is also possible to connect a Photovoltaic Solar Panel directly to a low voltage pump - as long as the panel and pump have similar power ratings - so the pump only runs when the sun is shining. The problem with this is that early in the morning the pump may send the previous day`s hot water from the tank to be cooled through the still cold solar water heating panel, and in the evening when the panel may be hotter than the contents of the tank, the pump will not run. The preferred system for most is to fit temperature sensors to the outlet from the solar water heating panel and to the hot water tank, and have an electronic differential temperature thermostat decide whether the pump should be turned on. This is a solar water heating pump controller. Pictured above is the solar water heating pump controller we first started selling back in 2006 (and still sell here: basic solar pump controller to this day). It has also been made by many of our site visitors following the plans below. This circuit is made up of just a few components. Key are the two temperature sensors ( LM335Z ) which are...

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