• Caleffi - iSolarPlus Controller - 257260A

    - with 2 Pump Speed Triacs, 4 Sensors and Vbus Connection

    Product ID • 257260A00000

  • $305.65
  • Quantity:
  • Free Ground Shipping


The iSolar 4 series solar thermal controllers are multi-funtional temperature differential controllers that provide complete control of the solar thermal system for safe and long-lasting operation. The iSolar 4 microprocessor controller monitors and controls thermal solar energy by means of a collector sensor and a storage tank sensor. The iSolar series controllers also implements important system monitoring and safety functions. The system parameters and measured values can be viewed and altered by the large LCD display.

The iSolar 4 controller is equipped with 4 temperature sensor inputs and 2 outputs for activating the solar curcuit and second output for activating a valve or second pump.

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Manuals & Docs

Technical Specs

Caleffi Solar Controller iSolar4- 257260A Specs

  • Selectable programs
  • Speed Control Triac Output (30 to 100%)
  • Sensor Inputs (temperature)
  • Max. Solar collector arrays
  • Max. Solar Storage tanks
  • Drainback pump peed control
  • Collector freeze protection
  • Evacuated tube collector function
  • Min collector temperature
  • Collector cooling functions
  • Tank (nighttime) cooling
  • Emergency shutdown functions
  • Operating hours counter
  • Energy metering measurement
  • Vbus data commincation

Caleffi Solar Controller iSolar4- 257260A Features

  • Delta T Controller - When the switch-on difference is reached, the pump is activated until the differential temperature drops below
  • Maximum tank temperature - When the adjusted maximum tank temperature is exceeded, the pump switches off
  • Collector emergency shutdown - If adjusted collector temperature is exceeded, the solar pump is switched off
  • System cooling - If the temperature rises to the maximum collector temperature the solar pump remains on until the temperature drops
  • Minimum collector temperature - a minimum set temperature which must be exceeded before the solar pump is switched-on
  • Antifreeze function - If the adjusted temperature drops, the solar pump is switched on to protect the fluid from freezing
  • Tank Cooling Function - In the evening, the solar pump continues running until the storage tank is cooled down
  • Tube Collector Function - The controller measures an increase of heat rise in the collector and adjusts operation for maximum efficiency
  • Heat Generation Measrurement KWh (BTu)- The heat generated is measured by the flow and the temperature of feed and return sensors
  • Operating hours counter - Operating hours counter stores the solar operating hours of the respective relay
  • Manual operating mode - For control and servicing, the operating mode of the controller can be switched manually

Info & Links

Solar Heating and Solar Domestic Hot Water with Flat Panels Example

Solar Heating / Solar Domestic Water with Evacuated Tubes and Boiler Example

Solar Domestic Hot Water, Solar Heating and Solar Pool Heating with Flat Panels

Solar Domestic Water with a Water Heater as a Backup Heat Source Example

Solar Panels for Domestic Water and Space Heating with a Boiler as the Backup Heat Source Example

Solar Panels for Domestic Water and Space Heating Pre-Heating into a Gas Combination Boiler Example

Solar Space Heating with a Backup Gas/Electric Boiler Installation Diagram

Hot Water Output examples for 3 locations

Solar Hot Water System Install - Waitsfield Vermont

Solar Hot Water System Install - Maine

Solar Hot Water System Install - Upstate New York

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