44 BAS-SVX44A-EN
Other Functional Components
Figure 23. Auto 3/heat and 2/cool systems
Other Functional Components
This section provides additional information for understanding thermostat operation or
programming. Some of the following sections refer to specific Option Numbers that are listed in
Table 7, p. 24.
Sleep Mode
Sleep mode places the CPU into a low power state when the thermostat is inactive.
Note: Sleep
mode is not implemented, but is noted here for future reference.
Changeover Operation
When the system is set to AUTO Mode, the thermostat automatically selects Cool Mode or Heat
Mode depending on the room temperature and the setpoint temperature. If the changeover setting
is set to manual, then AUTO Mode cannot be selected when selecting system type and the user
would need to manually change between Cool and Heat Modes. (Refer to 0180)
Changeover Valve Control
The changeover valve control (reversing valve O/B) is used only with heat pump systems.
Configuration Option Number 0153 determines whether the O/B signal is active for cooling or
heating (default is O/B active for cooling).
General Notes:
• The third auxiliary-stage heat output is only used for 3H/2C heat pump systems.
• The algorithm of cycling control is the same as the first-stage output. However, it has
independent cycle period setting.
• Both the first and second stage use the same temperature differential around setpoint for cycling
control.
• When the system is set for 3H/2C HP, the cycles for auxiliary heat (Option Number 0164) is used
for the third auxiliary heat stage.
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