The Fan 50 Plus Pins replaces Dinosaur’s earlier SMALL & LARGE fan boards as well as the Fan 50 Plus. It can also be used to replace the present fan control ignitor boards Being used by Suburban® and Atwood/Hydroflame®, but keep in mind that THE FAN CONTROL FEATURE MUST BE USED! In addition, the can also be used to UPGRADE an older furnace, giving it fan control features. The main features of the Fan 50 Plus Pins are (1) shut the fan motor OFF a minute and a half after the 3rd ignition try fails to sense a flame. And (2) wait one hour and try to cycle again before locking out and having to reset the thermostat.