Rheem Ruud 47 20545 92 Fan & Limit Control R 410A This 20A DPST relay features This 20A DPST relay features a 120 Vac power coil and is housed in a NEMA 1 rated enclosure Built to withstand the high heat cycles of commercial heating environments Optimized Blower Timing: Adjustable fan on (65 215°F) and fan off (50 200°F) settings allow for customized airflow timing to eliminate cold drafts at startup This HVAC fan limit control facilitates two primary functions: it cycles the blower fan on and off based on air temperature to maximize sensible heat recovery and acts as a high limit safety to break the burner circuit if the system reaches a 100 250°F threshold