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icomfort Wi-Fit 7−Day Programmable Communicating Thermostat
Page 33
Abbreviations:
FURN = auxiliary heat provided by gas furnace
HP = compressor heat
LBP = Low Balance Point
HBP = High Balance Point
T’stat = thermostat
Shut down FURN
Stg1...Stg 2
Operate HP
Stg 1...Stg 2
at or
below
LBP
FURN
heat
lockout
HP stage(s) operate first;
then FURN stage(s) (if
needed; see NOTE 1)
T’stat
heat
demand
?
NO
Shut down HP
Stg 1...Stg 2
YES
if
outdoor
temperature
is...
T’stat
heat
demand
?
Operate HP
Stg 1...Stg 2
NO
YES
Operate FURN
Stg 1...Stg 2
T’stat
heat
demand
?
YES
NO
Operate FURN
Stg 1...Stg 2
Heat
pump
lockout
T’stat
heat
demand
?
T’stat
heat
demand
?
YES
YES
NO
between
HBP and LBP
at
or above
HBP
COMPRESSOR ONLY
EITHER COMPRESSOR
OR FURN HEAT
FURN ONLY
50ºF
OUTDOOR TEMPERATURE
(defaults shown)
HBP − FURNACE
LOCKOUT TEMPERATURE
NOTE 1 − Each Heat Pump and Furnace Heat stage will oper-
ate until it meets the demand or until its stage timer lapses (20
minutes by default). If the timer lapses before the demand is
met, the system brings on the next stage in order of:
HP−stg−1, HP−stg−2, FURN−stg−1, FURN−stg−2.
NOTE 2 − The chart below illustrates how the balance points
control whether HP or FURN will operate to provide heat.
(See NOTE 2)
YES
NOTE 3 − If emergency heat is selected, Furnace is used.
25ºF
LBP − COMPRESSOR
LOCKOUT TEMPERATURE
Figure 35. Dual Fuel Operation with Balance Points