A two-stage upflow on a Ruud gas furnace refers to the number of operating modes and the direction of airflow. A two-stage furnace has two operating modes and air flows from bottom to top.
Ruud offers a number of gas furnaces in single- and two-stage models. A single-stage furnace responds to a need for heat by running at its full power until the desired temperature is reached. A two-stage model has an additional setting that is less than full power. It runs at this lower setting for a longer time and only goes to full power when needed. Two-stage furnaces are compatible with either one- or two-stage thermostats, but a two-stage thermostat is recommended for best performance.
An upflow furnace accepts cold air at the bottom of the unit, heats it, and then sends the warmed air out the top to the rest of the house. In a downflow furnace, the air flow is reversed. An upflow furnace is normally placed in a basement, while a downflow model is typically located in an attic.
In addition to the number of stages and air flow direction, Ruud offers furnaces with a variety of efficiencies and features to suit multiple home heating situations.