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T8775A,C THE DIGITAL ROUND
™
NON-PROGRAMMABLE THERMOSTATS
7 68-0279
Fig. 18. Room temperature display.
Adjust Temperature Setpoint
Turn the dial clockwise to raise the temperature setpoint. Turn
the dial counterclockwise to lower the temperature setpoint
(see Fig. 16).
Power Stealing
The T8775 thermostat steals power from R and W or Rc and
Y depending on the system switch position. See Table 3.
Table 3. T8775 Power Stealing.
The T8775 Thermostat only operates when mounted on the
wallplate with 24 Vac applied. Batteries are not required for
operation because the temperature setpoint is permanently
retained in memory.
Sequence of Operations
See Table 4 for Sequence of Operations.
Table 4. Sequence of Operations.
a
If fuel switch is set to E, both W and G are energized in a call for heat.
CHECKOUT
Cooling (T8775C only)
CAUTION
Low Temperature Hazard.
Operating at too low of an outdoor temperature
may cause compressor damage.
Do not operate cooling if outdoor temperature is below
50°F (10°C). Refer to manufacturer’s
recommendations.
Minimum Off-Timer
The minimum off-timer in the T8775C Thermostat assures
that the cooling compressor does not turn on for at least five
minutes after it turns off. The snowflake will flash in the display
if there is a call for cooling during the 5-minute off-time.
The following activates the 5-minute minimum-off timer:
• Initial startup
• Power interruption
• Compressor turns off:
— Setpoint is raised above the room temperature
— System switch is changed from the cool mode
— Thermostat ends the call for cooling
NOTE: The 5-minute minimum-off timer does not apply to
heating.
1. Slide the system switch to COOL and the fan switch to
AUTO.
2. Lower the temperature setpoint several degrees below
the room temperature.
3. A snowflake will appear in the display and the cool-
ing should turn on.
4. Raise the temperature setpoint several degrees above
the room temperature.
5. The snowflake
will disappear from the display and
the cooling should turn off.
Heating
1. Slide the system switch to HEAT and the fan switch to
AUTO (T8775C only).
2. Raise the temperature setpoint several degrees above
the room temperature.
3. A flame will appear in the display and the heat should
turn on.
4. Lower the temperature setpoint below the room temper-
ature.
5. The flame will disappear from the display and the
heat should turn off.
Fan
1. Slide the system switch to OFF and the fan switch to
ON. The fan should run continuously.
2. Slide the fan switch to AUTO. The fan should turn off.
NOTE: Make sure that all equipment responds properly to
the thermostat.
ROOM
SET
M1949
0
Power Stealing Circuit
System Switch T8775A T8775C
Heat R and W R and W
Off — R and W
Cool — Rc and Y
Fan Switch Settings System Switch Settings Call for Action Energize Terminals Display Icons
Auto Off None None None
Auto Heat Heating
W
a
Flame
Auto Cool Cooling Y,G
Snowflake
On Off Fan G None
On Heat Heating W,G
Flame
On Cool Cooling Y,G
Snowflake