Taco SR504-EXP-1 4-Zone Circulator Relay with Expansion Capabilities and Data Port

Original price was: $279.61.Current price is: $233.59.

9 in stock

SKU: 228805 Category:


Overall, the Taco SR504-EXP-1 offers a compact and expandable control solution for multi-zone hydronic heating systems. Its priority function, diagnostic lights, compatibility with various valve types, and expansion capabilities make it a versatile choice for efficient and customizable temperature control.


  • Controls water flow to 4 zones: Manages hot water circulation to individual zones in a hydronic heating system, ensuring efficient temperature control in different areas.
  • Activates and deactivates a circulator pump: Ensures continuous water circulation when needed, optimizing system performance.
  • Expandable for up to 120 zones: Can be linked with additional SR504-EXP-1 or SR506-EXP units to accommodate larger systems with more zones.

Key Features:

  • 4-zone capacity (expandable): Suitable for small to medium multi-zone systems, with the flexibility to expand as needed.
  • Switchable priority: Prioritizes one zone over others, ensuring immediate comfort or addressing critical areas when activated.
  • External diagnostic lights: Facilitate troubleshooting by indicating system status and zone operation.
  • Compact design: Optimizes space utilization in control panels.
  • Compatible with various valve types: Works with 2-, 3-, or 4-wire zone valves for flexibility in system design.
  • Built-in power ports for optional add-ons: Provides flexibility for future additions like a priority circulator or power vent controls.


  • Hydronic heating systems: Ideal for radiant, baseboard, or fan coil systems in residential and light commercial settings.
  • Closed cooling circuits: Can be used for zoned air conditioning systems.
  • Hydronic heating and cooling systems: Combines heating and cooling zones for year-round comfort.

Additional Features:

  • Field-replaceable transformer: Facilitates easy maintenance if needed.
  • Universal thermostat compatibility: Works with a wide range of thermostats.
  • Fuse-protected: Ensures electrical safety.

Things to Consider:

  • System compatibility: Verify compatibility with your system’s voltage, control signals, and valve types.
  • Installation complexity: While DIY installation is possible, consulting a qualified professional is recommended for optimal performance and safety.
  • Expansion modules: If you need more than 4 zones, additional SR504-EXP-1 or SR506-EXP units will be required.

Additional information

Weight 4.97 lbs


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