Schneider Electric R851V-8 8-Stage Step Controller with Integrated Vernier Output

The Schneider Electric R851V-8 is an 8-stage step controller designed for cost-effective, precise modulation of multi-stage heating control applications. This controller features integrated vernier stage technology for smooth, proportional control of HVAC equipment capacity from 0 to 100%.

Key Features:

• 8-stage step controller with integrated vernier output for heaters
• 24VAC operation with AC/DC isolated relay outputs
• Vernier stage output: 0-10Vdc (pulsed or analog), 5mA maximum
• Input impedance: 0-10Vdc into 10K Ohm
• Built-in test button for system diagnostics
• Master/slave capability - supports up to 16 stages when paired with slave unit
• Compact design for easy installation and integration

The R851V-8 delivers precise voltage control in incremental steps, minimizing electrical surges while ensuring smooth load transitions. The integrated vernier output provides full modulation capability, making it ideal for electric heating systems, commercial HVAC equipment, and industrial heating applications. This unit is the direct replacement for the obsolete R851V-4 model, offering enhanced control with double the stage capacity. Requires Class 1 or Class 2 transformer for power supply and relay outputs.