Six-Zone Switching Relay with Priority, 120 VAC

Taco SR506-EXP-4 – Six-Zone Switching Relay with Expansion Port

The Taco SR506-EXP-4 is a 120V AC switching relay panel designed for hydronic heating systems that require control of up to six circulator pumps. Compatible with both conventional and programmable thermostats, this unit simplifies multi-zone heating installations with integrated diagnostics and expansion capabilities.

Built for professional system integration, the SR506-EXP-4 supports external priority control, advanced boiler interface options, and plug-and-play compatibility with other Taco EXP modules.

Key Features

• Six-Zone Control: Supports up to six circulators with individual thermostat inputs
• Expansion Port: Integrates with Taco add-on modules for DHW priority, zone synchronization, and zone valve control
• LED Status Indicators: Diagnostic lights for zone calls, priority mode, and end switch activation
• Switchable Priority Function: Prioritizes domestic hot water or another designated zone
• Two Isolated End Switches: Separate dry contacts for boiler and system pump operation
• Pump Exercise and Post Purge: Preserves system reliability and extends circulator life
• Contractor-Optimized PC Board Layout: Labeled and accessible terminals for simplified field wiring
• UL Listed and Fuse Protected: Conforms to electrical safety standards with integrated overcurrent protection

Technical Specifications

• Input Voltage: 120 VAC, 60 Hz
• Thermostat Compatibility: 2-wire and 3-wire 24V thermostats
• Zone Capacity: 6 circulator zones (up to 20 zones with EXP modules)
• End Switch Contacts: SPST dry contacts rated for low-voltage boiler inputs
• Transformer: Field-replaceable 24V transformer
• Enclosure: Steel cabinet with knockouts for conduit or cable entry

Installation Guidelines

Designed for surface mounting, the SR506-EXP-4 offers a compact form factor suitable for mechanical rooms or zone panels. Thermostat and circulator connections are clearly identified, and the modular design allows integration with Taco's -EXP series accessories. A qualified HVAC or plumbing technician should perform all electrical wiring in accordance with local code requirements.

Application Notes

The SR506-EXP-4 is suited for hydronic systems requiring independent control of multiple circulators, such as baseboard, radiant floor, or fan coil applications. The integrated priority override makes it well-suited for systems incorporating an indirect-fired water heater.