Taco SR503-EXP-1 3-Zone Circulator Relay with Priority Zone Expansion Capabilities and Data

Original price was: $270.69.Current price is: $243.57.

11 in stock

SKU: 228804 Category:


The Taco SR503-EXP-1 3-Zone Circulator Relay is a versatile control unit for managing up to three separate circulator pumps in hydronic heating or cooling systems. Here’s a breakdown of its key features and functions:


  • Controls Circulator Pumps: Activates and deactivates up to three circulator pumps based on various control signals and configuration settings.
  • Three Zone Control: Each zone has independent control, allowing you to manage water flow to individual heating or cooling loops.
  • Switchable Priority: Prioritizes the operation of one zone over the others, ensuring critical areas receive heat or cooling first.
  • PowerPort Slots: Accepts optional PowerPort cards for additional features like external control inputs, zone valve control, and boiler sequencing.
  • Compact Design: Fits conveniently in tight spaces like control panels or boiler rooms.

Key Features:

  • External Indicator Lights: Provides visual feedback on system status and individual zone operation.
  • Fully Enclosed Snap-Out Relays: Ensures safe and reliable operation with easy access for maintenance.
  • Universal Thermostat Compatibility: Works with various types of thermostats for flexible control options.
  • Fuse Protected: Guards against electrical overloads for enhanced safety.
  • 100% Factory Tested: Ensures reliable performance and quality.


  • Hydronic Heating Systems: Ideal for controlling hot water circulation in radiant heating, baseboard heating, and fan coil systems.
  • Chilled Water Systems: Manages chilled water flow in zoned air conditioning systems.
  • Domestic Hot Water Recirculation: Controls water circulation in hot water recirculation systems for instant hot water at taps.

Things to Consider:

  • System Compatibility: Ensure the relay’s voltage and control signal types match your system requirements.
  • PowerPort Expansion: If you need additional features like zone valve control, consider purchasing compatible PowerPort cards.
  • Professional Installation Recommended: While DIY installation is possible for experienced individuals, consulting a qualified technician is recommended for safe and proper wiring and configuration.

Overall, the Taco SR503-EXP-1 is a versatile and reliable control solution for managing multiple circulator pumps in various hydronic heating and cooling systems. Its simple operation, expandable features, and compact design make it a popular choice for both residential and commercial applications.

Additional information

Weight 4.54 lbs


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