What is the 3-degree deadband in Auto changeover mode?
The 3-degree separation between heating and cooling set temperatures is a fixed feature that cannot be changed. When the system is set to Auto, the thermostat automatically selects heating or cooling depending on indoor temperature, and automatically adjusts settings to maintain this 3-degree separation called 'deadband'.
From the official Honeywell Focuspro TH5220D Thermostat manual, page 2
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