69-0778—1
2
WIRING AND MOUNTING
Replacement Applications
1. Disconnect power to wall thermostat to prevent elec-
trical shock or equipment damage. All wiring must comply
with local electrical codes and ordinances.
2. Remove the old thermostat from the wall, taking
care not to damage the wiring insulation.
3. Check the old wire insulation for cracks, nicks or
fraying. Apply approved electrical tape to insulate wires or
replace wires as necessary.
4. Remove the cover by grasping the top and bottom
edges and pulling outward away from the thermostat base.
5. Using wire connectors approved for No. 12 wires,
make line voltage connections directly to leadwires on the
thermostat. See Fig. 1 for typical wiring connections.
6. Prebend and push solid wires into the outlet box and
mount the thermostat on the outlet box using screws provided.
7. Tighten the two mounting screws to secure the ther-
mostat to the outlet box. See Fig. 2.
Fig. 1—Typical wiring connections.
New Applications
1. Run line voltage wiring to the thermostat location.
2. Install a vertical outlet box as instructed in Location
section.
3. Using wire connectors approved for No. 12 wires,
make line voltage connections directly to the leadwires on
the thermostat. See Fig. 1 for typical wiring connections.
4. Prebend and push solid wires into the outlet box and
mount the thermostat on the outlet box using screws provided.
5. To access the thermostat mounting screws, remove
the cover by grasping both the top and the bottom edges and
pulling outward away from the thermostat base. Tighten
the two mounting screws to secure the thermostat to the
outlet box. See Fig. 2.
Initial Powerup
On initial power-up, the thermostat will display “SC”
for 15 seconds, indicating that the system is operating
properly. If an “E” flashes continuously, the thermostat is
defective. Contact your Honeywell dealer for a replace-
ment thermostat.
Next, the operating condition “occupied-dark” will flash
for two minutes while the thermostat program is being
initialized. After initialization, the actual operating condi-
tion will be indicated.
The room temperature will not be displayed for the three
minutes immediately following powerup.
PROGRAMMING
The T4798S Thermostat microprocessor-based control
automatically adjusts the temperature to the preset tem-
perature depending on the occupancy and lighting in the
controlled space.
The T4798S can be programmed to select temperatures,
light level, and Fahrenheit or Celsius temperature display.
Tap the SEL key to move between modes. The display
changes in the following order: occupied-light, unoccu-
pied-light, unoccupied-dark, occupied-dark, L, F or C. See
Fig. 3.
Fig. 3—Features of the T4798S Thermostat.
L1
T1
SOLDERLESS
CONNECTORS
L1
(HOT)
L2
3
2
ELECTRIC
HEATER
2
POWER SUPPLY. PROVIDE DISCONNECT MEANS
AND OVERLOAD PROTECTION AS REQUIRED.
SPECIAL SERVICE CO/ALR SOLDERLESS CONNECTORS
MUST BE USED WHEN CONNECTING WITH ALUMINUM
CONDUCTORS; OTHERWISE, A FIRE HAZARD MAY RESULT.
TRIAC CONDUCTS EVERY 15 SECONDS UNLESS ROOM
TEMPERATURE IS ABOVE SETPOINT.
3
1
1
M3643
Fig. 2—Mounting T4798S on outlet box.
M3635
COMFORT
ECONO
SET
SEL
VERTICAL
OUTLET
BOX
THERMOSTAT
BASE
MOUNTING
SCREWS (2)
THERMOSTAT
COVER
M9072
COMFORT
ECONO
SET
SEL
MODE SYMBOLS
LCD DISPLAY
TEMPERATURE SETTING
SELECT KEY FOR
CHANGING FROM
MODE TO MODE
LIGHT SENSOR WINDOW
SET KEY FOR CHANGING
THE SETTINGS IN
MODES OR READING
ROOM TEMPERATURE
MODE INDICATOR
SHOWS WHICH MODE
IS OPERATING