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5. Heat pump
(See Fig. 25 -- 32 for thermostat connections.) When
installed with a heat pump, the furnace control
automatically changes the timing sequence to avoid long
blower off times during demand defrost cycles. When the
R -- t o -- W -- a n d -- Y 1 o r R -- t o -- W -- a n d -- Y 1 -- a n d -- G c i r c u i t s
are energized the furnace control CPU will switch to or
turn on the blower motor BLWM at HEAT speed, and
begin a heating cycle. The blower motor BLWM will
remain on until the end of the prepurge period, then shut
off for 24 seconds then come back on at HEAT speed.
When the W input signal disappears, the furnace control
begins a normal inducer post--purge period and the blower
remains running at HEAT speed for the selected
blower--OFF delay period then switches to low --cool
speed (same speed as FAN). If the
R--to--W--and--Y1 --and--G signals disappear at the same
time, the blower motor BLWM will remain on for the
selected blower--OFF delay period. If the R--to--
W--and--Y1 signals disappear, leaving the G signal, the
blower motor BLWM will remain on for the selected
blower--OFF delay period then switch to
continuous-- blower speed. When the R --to--W--and--Y/Y2,
R--to--W--and--Y/Y2--and--G, R--to--W--and--Y1--and--
Y / Y 2 , o r R -- t o -- W -- a n d -- Y 1 -- a n d -- Y / Y 2 -- a n d -- G c i r c u i t s
are energized the furnace control CPU will switch to or
turn on the blower motor BLWM at HEAT speed, and
begin a heating cycle. The blower motor BLWM will
remain on until the end of the prepurge period, then shut
off for 24 seconds then come back on at HEAT speed.
When theWinput signal disappears, the furnace control
begins a normal inducer post--purge period and the blower
switches to COOL speed after a 3 second delay. If the
R -- t o -- W -- a n d -- Y / Y 2 -- a n d -- G o r R -- t o -- W -- a n d -- Y 1 -- a n d --
Y/Y2--and--G signals disappear at the same time, the
blower motor BLWM will remain on for the selected
blower--OFF delay period. If the R--to--W--and--Y/Y2 or
R--to--W--and--Y1 --and--Y/Y2 signals disappear, leaving
the G signal, the blower motor BLWM will remain on for
the selected blower--OFF delay period then switch to
continuous blower speed.
Wiring
Diagrams
Refer to Fig. 59 for wiring diagram.
Tr
oubleshooting
Refer to the service label. (See Fig. 55.) The Troubleshooting
Guide (See Fig. 60) can be a useful tool in isolating furnace
operation problems. Beginning with the word “Start,” answer
each question and follow the appropriate arrow to the next item.
The Guide will help to identify the problem or failed component.
After replacing any component, verify correct operation
sequence.
58PHA