Lochinvar & A.O. Smith 100271885 Probe R 410A this board ensures the ignition this board ensures the ignition sequence and safety limit monitoring meet original manufacturer requirements for safe and predictable system operation Standardized Output: The 500 Ohm Nickel signal is the industry standard for a wide range of legacy building automation controllers This OEM replacement part includes a robust integrated connector to ensure seamless electrical continuity and accurate resistance signaling to the control board Designed specifically for high efficiency systems like the BTH series gas water heaters (including BTH 150 through BTH 500 models)