Robertshaw RS5220C User Manual page 8

DIFF = The differential keeps the thermostat from turning on for small
changes in temperature. When in Fahrenheit the range is 0.5 to
3.0 Degrees. In Celsius the range is 0.5 to 1.5 Degrees. The
differential is factory set at 1.0 °F (0.5 °C). This means that
whenever the room temperature is more than 1 °F (0.5 °C)
different from the set temperature the system will turn on. If the
system is turning on too often, increase the differential setting.
Note that a larger differential will mean the room temperature
changes more before the system turns on.
DIF2 = Second Stage Differential = Operates with the first stage to
control a second heating/cooling system. This number will be
added to the first stage differential (See: Two Stage Systems).
If the first stage is running too often lower the settings. This will
turn the second stage on to help the first stage. If both stages
are coming on too often then increase this setting to delay the
second stage.
DLY2 = Second Stage Delay = This timer starts when the first stage turns
on. It resets when the first stage turns off. If this timer runs out
the second stage will turn on (See Two Stage Systems).
Auto changeover enable = Makes the auto changeover mode available.
When chosen, the thermostat can automatically switch between
heating and cooling. Note that the High and Low setpoint limits
are not enforced in auto changeover mode.
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