Honeywell TRADELINE T4798S User manual

1 69-0778—1
T4798S
Programmable Electric
Heat Thermostat
J. H. • Rev. 12-93 • ©Honeywell Inc. 1993 • Form Number 69-0778—1
TRADELINE
Application
The T4798S Programmable Electric Heat Thermostat
provides automatic line voltage control of electric resis-
tance heating equipment. The T4798S Thermostat senses
light and motion to choose the appropriate setpoint based on
four operating modes:
—Occupied-light
—Occupied-dark
—Unoccupied-light
—Unoccupied-dark
Thermostat has an adjustable light level threshold for
light sensing:
—most sensitive-dark
—less sensitive-dim
—least sensitive-light
Uses wide-angle passive infrared motion detection.
Thermostat retains programming during power failure.
Proportional, integral plus derivative microprocessor con-
trol provides accurate temperature control; triac-based
switching. The T4798S Thermostat can be used as a ther-
mometer; display can convert between Fahrenheit and
Celsius temperature. Allows easy two-wire installation.
Suitable for residential or commercial electric baseboard
heating applications. Not for use in central electric heating
systems or with inductive loads.
TEMPERATURE SETTING RANGE: 44 °to 80°F [7°to
27°C].
PROPORTIONAL BAND (REGULATION): 0.9°F [0.5°C].
ELECTRICAL RATINGS:
Voltage/Frequency: 208 to 240 Vac, 50/60 Hz.
Power Rating:10.5A maximum (2200 to 2500W); non-
inductive resistive load.
Power Consumption (Off): 560 mW.
WIRING CONNECTIONS:
Two 6 in. [150 mm] copper leadwires (suitable for con-
necting to aluminum wiring if approved CO/ALR
connectors are used).
APPROVALS:
Underwriters Laboratories Listed: File No. E136167,
Guide No. XAPX.
Canadian Standards Association Certified: File No.
LR91801-1.
Canadian Standards Association Performance Certified:
Standard C273.4A.
Installation
WHEN INSTALLING THIS PRODUCT...
1. Read these instructions carefully. Failure to fol-
low these instructions could damage the product or cause a
hazardous condition.
2. Check the ratings on the product to make sure the
product is suitable for your application.
3. Installer must be a trained, experienced service
technician.
4. After installation is complete, check out product
operation as provided in these Instructions.
WARNING
HIGH VOLTAGE CONTROL.
ELECTRICAL SHOCK HAZARD.
Follow local codes and ordinances when install-
ing this thermostat. Improper handling may cause
serious injury or death.
CAUTION
1. Disconnect power supply to prevent electrical
shock or equipment damage.
2. If connecting with aluminum conductors, use
CO/ALR solderless wire connectors to avoid
fire hazard.
3. Keep the air vents on both the top and the
bottom of the thermostat clean and free from
obstructions to prevent overheating of the unit.
IMPORTANT: Do not use this thermostat with central
electric heating systems, or fan-forced heaters.
LOCATION
Mount this thermostat on a vertical outlet box. Install a
vertical outlet box about 5 ft [1.5m] above the floor in an
area with good air circulation at room temperature.
Do not install the thermostat where it can be affected by:
— drafts or dead spots behind doors, in corners or under
cabinets.
— hot air from convectors.
— radiant heat from sun or appliances.
— concealed pipes and chimneys.
— unheated (uncooled) areas such as an uninsulated
outside wall behind the thermostat.
!
!
This equipment is a Class B digital apparatus which com-
plies with Canadian Radio Interference Regulations, CRC
c.1374.

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

3 69-0778—1
NOTE: To lessen temperature changes when an occupant
leaves an area, the T4798 will not change from an
occupied to unoccupied setting for 60 minutes (light
setting) or for three hours (dark setting). If a pet is
activating the program, cover up the lower half of the
sensor window or program temperature changes for
only light and not occupancy.
Select Fahrenheit or Celsius Temperature Display
Select Fahrenheit or Celsius by tapping the SEL key
until F or C appears in the LCD display. Tap the SET key
to select the setting.
NOTE: If programming in Fahrenheit, only even numbered
temperatures (i.e., 66, 68, 70) can be selected. The
temperature setting range is 40°to 86°F [5°to 30°C].
Program Temperature Settings
To set the temperatures, tap the SEL key until the
indicator points to the desired mode (i.e., occupied-dark).
Press the SET key to select the desired temperature.
Repeat for each mode. See Table 1.
Select Light Level
To set the light level, tap the SEL key until the LCD
displays L1, L2 or L3. Tap the SET key to change the light
setting.
NOTE: When setting the light level, consider the ambient
outdoor and indoor lighting over a 24-hour period. The
three light level settings are: L1—the most sensitive so it
is used when the thermostat will respond to a low light
level like the TV or reading light; L2—average setting
so it is used for most rooms; L3—the least sensitive
setting so it is used in well-lit areas.
Review Program
To review the program, tap the SEL key to scroll be-
tween settings. To change any setting, tap the SET key until
the display shows the desired setting.
Reading Current Temperature
To read the current temperature, tap the SET key. The
room temperature and four indicators will be displayed for
about ten seconds. The display range is 40°to 86°F [5°to
30°C].
NOTE: When the room temperature is warmer than 86°F
[30°C], the two upper indicators will be displayed.
When the room temperature is colder than 40°F [5°C],
the two lower indicators will be displayed.
Loss of Power
The T4798S maintains the program during loss of power
without batteries. The display will go blank. When power is
restored, the display will go through the steps in the Initial
Powerup section.
aAlthough programmed settings may be at any temperature, make sure that “unoccupied” settings are below
“occupied” settings for energy savings.
bTypical electromechanical line voltage thermostats may control the temperature 2°to 4°F [1°to 2°C] below the
programmed setpoint dial setting. The T4798S thermostat controls the temperature at the programmed setpoint. It is
recommended that you program the “comfort” temperature setpoint 2°to 4°F [1°to 2°C] below the setting of the
thermostat that is being replaced to avoid overheating the space.
TABLE 1—SAMPLE PROGRAMSa,b.
Kitchen Living or Family Room Bedroom
Mode Remarks Temp. Setting Remarks Temp. Setting Remarks Temp. Setting
Occupied-light Set for a comfortable
temperature for eating or
cooking.
68°F
[20°C] Set for a comfortable temperature for reading or
watching TV.
68°F
[20°C] Set for a comfortable temperature for getting up
in the morning.
68°F
[20°C]
Unoccupied-light Set the temperature desired
when you are out of the room
in the daytime.
60°F
[15°C] Set the temperature desired when you are out of the
room in the daytime.
60°F
[15°C] Set the temperature desired when you are out of the
room in the daytime.
60°F
[15°C]
Unoccupied-dark Program for when no one is
using the kitchen. 60°F [15°C] Program for when no one is using the room. 60°F [15°C] Program for when no one is using the bedroom. 60°F [15°C]
Occupied-dark This mode is primarily for
sleeping rooms. Set
temperature desired when no
one is using the kitchen.
60°F
[15°C] This mode is primarily for sleeping rooms. Set
temperature desired when no
one is using the room.
60°F
[15°C] Set desired temperature for sleeping. 62°F [16°C]
LIGHT LEVEL Use the least sensitive setting
so the thermostat does not
sense the light from an open
refrigerator door at night.
L3 Use the most sensitive
setting so the thermostat will
sense the tv or small reading
light.
L1 Use the average setting. L2
M5625

69-0778—14
QUALITY IS KEY
Operation
The T4798S Thermostat controls the room temperature
to the preset temperature depending on the occupancy and
lighting in the controlled space. The thermostat responds to
the occupancy and light conditions by selecting the preset
temperature for the operating mode. The temperature is
adjusted to maximize both comfort and energy savings.
The SEL key allows selection of one of the four operat-
ing modes. The SET key enters the operating mode, allow-
ing changes to be made. The thermostat liquid crystal
display (LCD) indicates the current operating mode and
setpoint. The room temperature is displayed for ten seconds
by pressing and releasing the SET key.
The light sensing level of the thermostat can be chosen
from one of three conditions:
—L1 indicates most sensitive; thermostat reacts to the
minimum amount of light. This is typically used to
detect artificial lighting or “evening”.
—L2 indicates less sensitive; thermostat reacts to a
little more than the minimum amount of light.
—L3 indicates least sensitive; thermostat reacts to the
highest amount of light. This is typically used to
detect lighting or solar gain. It is useful for rooms that
face west or south.
The thermostat does not require batteries and maintains
the program during a power failure. It is not necessary to
reprogram the thermostat when there is a change in daily
schedule or for daylight savings time.
The microprocessor proportional, integral plus derivative
algorithm controls the duty cycle to accurately maintain the
temperature setpoint during all operating conditions.
NOTE: The T4798S thermostat does not have a clock;
therefore, it does not adjust the room temperature to warm
up the room until the room is occupied. Derivative con-
trol will warm up the space as fast as the heaters can.
The thermostat triac controls electric convectors propor-
tionately to the heating load of the room. The triac cycles
240 times per hour, turning on longer as the load increases.
At this cycle rate, the heating element is always warm
except during warm-up periods when it is hot. This makes
it safer for children who may play near convectors. It also
provides more comfort since the air is always circulating,
which eliminates the dark streak above hot baseboard heat-
ers.
The high cycle rate makes the T4798S uncompatible
with inductive loads such as fans, relays and pumps. The
T4798S is for use only with resistive loads.
NOTE: To minimize room temperature fluctuations, the
thermostat will not change from an occupied to unoccu-
pied mode for 60 minutes (for light) or for three hours
(for dark) when an occupant leaves the controlled space.
This equipment is a Class B digital apparatus which complies with Canadian Radio Interference Regulations, CRC c.1374.
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