Dual-Mode Functionality: Supports both single-probe point level detection and three-probe differential control for automated pump cycles

Can I use this relay for both AC and DC switching on the contact side

providing seamless mechanical and electrical compatibility with legacy unit heaters

This harness is designed for specific Carrier and RCD-branded furnace models

and mounting hardware to streamline field installations

Lochinvar & A.O. Smith 100277781 Control 321894-706 Dual-Mode Functionality: Supports both single-probeThe Lochinvar 100277781 Control (Model FB751 1251) is an integrated control board engineered specifically for Crest Heating Boilers. As a critical OEM replacement part, this module manages the firing sequence, ignition control, and safety parameters for high efficiency hydronic systems. This model is a direct boiler part replacement for units with serial numbers beginning with 4015, ensuring seamless integration with existing HVAC wiring harnesses and