Carrier Access Thermidistat - Manual (Page 6)

will be supplied, resulting in additional outputs being turned on. If
room overheats, specified outputs will not turn off, guaranteeing a
sufficiently warm leaving air temperature during defrost. Tempera-
ture overshoot during defrost can occur, but is almost never
noticeable because of the short duration of the defrost cycle (4
minutes typical, 10 minutes maximum).
An additional feature of Thermidistat Control defrost is that it
always allows defrost cycle to run to completion. The Thermidistat
Control leaves the Y output on as long as outdoor unit holds
voltage on the O line, even if it is satisfied. This prevents
premature termination of defrost cycles, which occur with normal
thermostats.
TO SELECT:
1. Enter configuration mode if not already there. See Step 4 "To
Enter Configuration Mode." Use up and down buttons to make
small (now flashing) display indicate 12.
2. Press SET TIME/TEMP button once to flash large display.
3. Use up or down buttons to move between 0, 1, 2, or 3 (if
available) on large display. See Table 1 for effect of these
choices. Factory default is 0.
4. Press SET TIME/TEMP button again to flash upper small
display for selection of another option, or press END to exit
configuration mode.
Option 13—Room Temperature Offset Adjust
This option allows calibration (or deliberate miscalibration) of
room temperature sensor. There are various reasons why home-
owners may want to have displayed temperature adjusted to a
higher or lower value. The selected number is number of degrees
farhenheit, plus or minus, which will be added to actual tempera-
ture. The numbers can range between -5 and +5. Factory default is
0. This adjusted value will be used as actual temperature for both
display and control action. For example, if 2 is selected, 72°F
actual will read 74°F. If set point is 72°F, the room will control to
an actual temperature of 70°F which will be displayed and acted
upon as if it were 72°F. The effect is that a positive number
selection will make the room temperature lower and vice versa.
The Thermidistat Control is calibrated within an accuracy of plus
or minus 1°F when shipped from the factory, so this adjustment
will provide the best accuracy when set to 0.
TO SELECT:
1. Enter configuration mode if not already there. See Step 4 "To
Enter Configuration Mode." Use up and down buttons to make
small (now flashing) display indicate 13.
2. Press SET TIME/TEMP button once to flash large display.
3. Use up or down buttons to move between -5, -4, -3, -2, -1, 0,
1, 2, 3, 4, or 5 on large display. Factory default is 0.
4. Press SET TIME/TEMP button again to flash upper small
display for selection of another option, or press END to exit
configuration mode.
Option 14—Heat/Cool Dead Band Adjustment
This option selects the minimum difference between heat and cool
set points. A larger difference saves energy and a smaller differ-
ence decreases temperature difference between heating and cool-
ing. Factory default is 2, which means cooling set point must be a
minimum of 2° above heating set point. An attempt to move them
closer will result in one "pushing" the other to maintain the
required difference.
Depending on set points, moving dead band closer than 2° may
result in regular cycling between heat and cool when AUTO mode
is selected. However, this cycling cannot occur more often than 1
transition every 20 minutes. The system has a built-in requirement
that it cannot switch between heat and cool without a 20 minute
"off" time between the 2 operations. Specifically, to switch from 1
mode to the other, there must be no demand for the old mode and
a demand for the new mode, and this must exist continually for 20
minutes before transition to the new mode will occur.
TO SELECT:
1. Enter configuration mode if not already there. See Step 4 "To
enter Configuration Mode." Use up and down buttons to make
small (now flashing) display indicate 14.
2. Press SET TIME/TEMP button once to flash large display.
3. Use up or down buttons to move between 0, 1, 2, 3, 4, 5, or 6
on large display. Factory default is 2.
4. Press SET TIME/TEMP button again to flash upper small
display for selection of another option, or press END to exit
configuration mode.
Option 15—Enable Auto Mode
This option allows the installer to enable or disable AUTO mode
(automatic changeover between heat and cool). When disabled,
AUTO icon does not appear when successive presses of MODE
button are used to move between OFF, HEAT, COOL, and
EHEAT (in heat pump systems). Factory default is ON (AUTO
enabled).
TO SELECT:
1. Enter configuration mode if not already there. See Step 4 "To
Enter Configuration Mode." Use up and down buttons to make
small (now flashing) display indicate 15.
2. Press SET TIME/TEMP button once to flash large display.
3. Use up and down buttons to move between OF and ON on
large display. Factory default is ON (AUTO enabled).
4. Press SET TIME/TEMP button again to flash upper small
display for selection of another option, or press END to exit
configuration mode.
Option 16—Enable Super Comfort Heat Mode
This option requires prior ON selection of heat pump (DIP switch
No. 1) and Configuration Option No. 5 (Select Variable-Speed
Blower). Super Comfort Heat mode is part of the Comfort Heat
Pump system, which comprises a selected combination of Ther-
midistat Control, variable speed Fan Coil, and 3-stage electric
heater to provide superior heat pump leaving air temperatures
under all conditions. This option selection modifies heat pump
blower and auxiliary heat operation to contribute to comfortable
leaving air temperature. Specifically, this selection provides:
• Reduced heat pump airflow for outdoor temperatures between
12° and 40°F.
• At least 1 stage of electric heat ON for all heating below 12°F.
While outdoor air temperature is between 12°F and 40°F, the
Thermidistat Control removes the G signal during heat pump
heating. The 40FK, FK4C, or FV4A Variable-Speed Fan Coils
respond by reducing their airflow in the absence of the G signal,
raising leaving air temperature. For any heating demand below
12°F, G and W/W1 are turned ON, assuring at least 1 stage of
electric heat is on, and also increasing leaving air temperature.
As part of the Comfort Heat pump system, Configuration Option
No. 9 (Intelligent Heat Staging) should also be set to ON if the heat
pump is single stage and a 3-stage heater is present.
TO SELECT:
1. Enter configuration mode if not already there. See Step 4 "To
Enter Configuration Mode." Use up and down buttons to make
small (now flashing) display indicate 16.
2. Press SET TIME/TEMP button once to flash large display.
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