American Standard 340 - Manual (Page 6)

6
Pub. No. 12-5026-01
69-1609
RETURN Choose the time you want your heating or cooling system to start to
reach your comfort temperature after the energy-savings LEAVE
period.
How? Consider the time required to reach your comfort level. Adjust the
Return time to earlier when you know it will take the system longer to
reach your comfort temperature.
SLEEP Set the time you want your heating or cooling system to start to reach
your Sleep temperature.
To use this period as an energy-savings mode, set the temperature
lower during heating season, and higher during cooling season.