How do I set the R and U slider tabs on the UWP?
The R Slider Tab differentiates between one or two transformer systems: set to up position (1 wire) if one R wire is connected, or down position (2 wires) if separate R and Rc wires are connected. The U Slider Tab controls ventilation: set to down position (2 wires) for dry contacts or up position (1 wire) if powered by the cooling transformer.
From the official Honeywell Lyric T6 Pro Wi-Fi Smart Thermostat manual, page 4
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