icomfort Touch
7−Day Programmable Communicating Thermostat
Page 19
Heat Pump, Dual Fuel and Balance Points
NOTE − The Balance Points feature requires an outdoor sen-
sor to be installed and enabled. The outdoor temperature
sensor is included in all icomfort
t
−enabled heat pumps. The
optional outdoor temperature sensor X2658 must be installed
and enabled for use of the Balance Points feature with non−
communicating heat pumps.
Heat Pump Balance Points
The LOW and HIGH set points may be controlled by the icom-
fort Touch
thermostat using the LOW and HIGH Balance
Points feature. To enable the Balance Points feature, go to
the installer section equipment tab. Scroll down to the System
49W95 screen, select
edit
and scroll down to Balance Points
Controls. Use arrows to select
Enabled
and then press
save
.
See the flowchart for a simplified explanation of how balance
points control system operation.
Low Balance Point
If the outside temperature is below the programmed low bal-
ance point (set by default at 25°F), compressor operation is
not allowed. Since the heat pump is not as effective at a lower
outdoor temperatures, it may be more comfortable to use the
auxiliary electric heat or the furnace (in dual fuel systems, it
may be more economical) to satisfy a demand for heat. The
low balance point options are from −20°F to the high balance
point temperature. The set point can be adjusted in 1.0°F
steps. Again, the Balance Points feature is only available if an
outdoor sensor is installed (standard on icomfort
−enabled
heat pumps).
High Balance Point
If the outside temperature is above the programmed high bal-
ance point (set by default at 50°F), auxiliary electric heat op-
eration or furnace operation (in dual fuel system) is not al-
lowed. This ensures that the lower cost heat pump operation
will satisfy the heating demand, rather that the more expen-
sive auxiliary electric heat. The high and low balance points
will not lock out both compressor heat and auxiliary heat/fur-
nace at the same time. Again, the Balance Points feature is
only available if an outdoor sensor is installed (standard on
icomfort
−enabled heat pumps).
Dual Fuel Applications (Communicating Systems
Only)
Dual fuel applications, which include both a Heat Pump and a
furnace (gas or oil), will provide multiple stages of heating.
For example, a two−stage heat pump would deliver two
stages of heat. The gas furnace can add two to four more
stages of heat. Figure 52 flow chart illustrates Dual Fuel op-
eration with Balance Points.
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 TEMPERA
TURE
(defaults shown)
HBP − FURN
LOCKOUT
TEMPERATURE
LBP − COMPRESSOR
LOCKOUT
TEMPERATURE
NOTE 1 − Each Heat Pump and Furnace Heat stage will operate 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
Figure 52. Dual Fuel Operation with Balance Points
