Single-Zone Switching Relay, 120 VAC

Taco SR501-4 Single Zone Switching Relay – 120V Input, 24V Thermostat Control

The Taco SR501-4 is a single-zone switching relay designed to control one circulator pump based on a 24V thermostat demand. Commonly used in residential hydronic heating applications, this relay offers reliable performance and straightforward integration with standard heating components.

The unit includes an isolated end switch for boiler or system control, front-facing LED indicators for power and zone status, and simplified terminal connections for fast installation. Designed with contractor efficiency in mind, the SR501-4 is compatible with both analog and digital thermostats.

Key Functional Features

• Single Zone Control: Activates one circulator pump per thermostat demand
• End Switch: Isolated end switch to trigger boiler or primary system control
• LED Diagnostics: Visual indication for power and zone call status
• Fuse Protection: Internal circuit protection for safe operation
• Factory Tested: 100% function-tested prior to shipment
• Compact Design: Mountable enclosure for space-limited applications

Technical Specifications

• Model: SR501-4
• Zones: 1 (single circulator output)
• Input Voltage: 120 VAC, 60 Hz
• Thermostat Input: 24 VAC
• Pump Output: 120 VAC
• End Switch Rating: 24 VAC dry contacts
• Relay Type: Enclosed, field-serviceable

Installation Overview

The SR501-4 is designed for fast, efficient installation with clearly labeled terminal blocks and a straightforward layout. The unit is suitable for mounting on a wall or control panel. Professional installation is recommended to ensure correct wiring and compliance with electrical codes, especially when integrating with boiler or multi-zone systems.

Application Notes

This model is ideal for single-zone residential systems, including baseboard, radiant, and fan coil heating. It can be used to control a dedicated circulator or zone pump, with thermostat input triggering pump activation and boiler demand via the end switch.