Caleffi ZSR103 Z-one 3-Zone Pump Switching Relay with Priority Control

The Caleffi ZSR103 Z-one Relay is a professional-grade multi-zone pump and boiler operating control designed for hydronic heating and cooling systems. This expandable switching relay manages up to three zone circulator pumps plus one primary system pump, providing precise control and efficient operation for residential and light commercial applications.

Key Features:

• Controls up to 3 zone pumps and 1 primary pump with 120 VAC/5A outputs each
• Compatible with 2, 3, and 4-wire low voltage thermostats (24 VAC)
• Zone priority selectable with 1-hour timeout feature for domestic hot water priority
• Built-in 12 VA transformer with automatic resettable fuse protection
• Heavy-duty sealed relays rated for 20 amps combined load
• Front panel LED indicators for functional status and easy troubleshooting
• Expandable to unlimited zones using simple 3-wire connection between controls
• Large screw terminals with R, W, C and T, T, COM dual labeling for simplified wiring
• Dry contact auxiliary outputs (XX, AUX, ZONE 1 E/S) capable of switching line voltage
• Selectable post-purge and pump exercising functions
• Durable ABS housing rated to 110°F operating temperature

Specifications:

• Power Supply: 120 VAC, 50/60 Hz
• Transformer Output: 24 VAC, 12 VA
• Relay Rating: 5A per zone output, 20A maximum combined
• Dry Contact Rating: 120 VAC, 2A each
• Dimensions: 11" W x 3" D x 9.25" H
• ETL certified to CSA C22.2 No. 24, conforms to UL 873
• 3-year manufacturer warranty

The ZSR103 features an installer-friendly design with ample room for terminations, snap-in transformers, and three dedicated pump ground terminals for simplified wiring. Perfect for multi-zone radiant floor heating, baseboard systems, and mixed heating/cooling applications.