Lennox Dave Signature XP21 Installation Instructions Manual page 8

PREVIOUS TERMINATION
TEMPERATURE
<70ºF OR UNKNOWN
≥70ºF, <90ºF
≥ 90ºF
MAX DEFROST
TERMINATION TEMPERATURE
FOR NEXT DEFROST CYCLE
90ºF
MAX DEFROST
MAX DEFROST
MAX DEFROST
FIGURE 8. Auto Defrost Rule
Page 8
NOTE: Testing indicated
that the highest potential
for a weather event to
prevent fan operation due
to ice build up on the fan
blade and orifice ring is
when the outdoor ambient
is below 35ºF and the unit
is OFF for more than 30
minutes.