Robertshaw RS6000 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).
DLY3 = Third Stage Delay = This timer starts when the second stage turns
on. It resets when the second stage turns off. If this timer runs
out the third stage will turn on. (See Three Stage Systems).
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