CONTENTS
Installation Instructions for
Preparations.................................................. 1
Thermostat Details ........................................ 1
Removing Old Thermostat ............................ 1
Mounting and Wiring ..................................... 2
Check Thermostat Operation ........................ 3
Specifications ................................................ 5
Troubleshooting ............................................ 5
Heating & Air Conditioning
1F78
Non-Programmable Thermostat
YOUR THERMOSTAT REPLACES
PREPARATIONS
1
Typical System Compatibility Chart
1F78
Standard Heat Only Two Wire Gas or Oil Fired Systems (24 volt)
Electronic Ignition Heat Only Two Wire Systems (24 volt)
Electronic Ignition Heat Only Gas or Oil Fired Systems (24 volt)
Standard Heat/Cool Systems (24 volt)
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
No
Assemble tools required as shown below.
FLAT BLADE SCREWDRIVER
Heat/Cool Systems Electric Heat (24 volt)
Heat Only Electric Heat Systems (24 volt)
Cool Only Systems (24 volt)
HAND OR POWER
DRILL WITH 3/16 INCH
DRILL BIT, IF NEEDED
Heat Pump Systems (No Aux or Emergency Heat)
Hot Water Zone Heat Only (Two Wire) Systems
Hot Water Zone Heat Only (Three Wire) Systems
Line Voltage Heating or Baseboard 110/240 Volt Systems
Millivolt Systems Floor or Wall Furnaces
WIRE CUTTER/STRIPPER
No
Yes
Yes
No
12 VDC Mobile Home Application
Failure to follow and read all instructions carefully
before installing or operating this control could cause
personal injury and/or property damage
Multistage Systems
Systems Exceding 30VAC, 1.5 Amp
No
THERMOSTAT DETAILS
REMOVING OLD THERMOSTAT
2
3
Mounting
hole
CAUTION
!
To prevent electrical shock and/or equipment damage,
disconnect electrical power to the system at the main
fuse or circuit breaker until installation is complete.
-
-
+
+
Before removing wires from old thermostat’s switching subbase,
label each wire with the terminal designation it was removed from.
W
RH
B
RC
1. Remove Old Thermostat: A standard heat/cool thermostat
consists of three basic parts:
a. The cover, which may be either a snap-on or hinge type.
b. The base, which is removed by loosening all captive screws.
G
O
Y
Mounting
hole
W904
W905
W905
Clip for
Hydronic
System
c. The switching subbase, which is removed by unscrewing
themountingscrewsthatholditonthewalloradaptorplate.
ELEC GAS
2. Shut off electricity at the main fuse box until installation is
complete. Ensure that electrical power is disconnected.
3. Remove the front cover of the old thermostat. With wires still
attached,removewallplatefromthewall.Iftheoldthermostat
has a wall mounting plate, remove the thermostat and the wall
mounting plate as an assembly.
W904
Clip for
Celsius Display
Electric/Gas
Switch
Figure 1. Thermostat base
4. Identifyeachwireattachedtotheoldthermostatusingthe
labels enclosed with the new thermostat.
5. Disconnectthewiresfromtheoldthermostatoneatatime.DO
NOT LET WIRES FALL BACK INTO THE WALL.
6. Install new thermostat using the following procedures.
White-Rodgers is a division
of Emerson Electric Co.
PART NO. 37-6615A
0435
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MOUNTING AND WIRING
CONTINUED FROM SECOND PAGE
4
JUMPER
THERMOSTAT
SYSTEM
Hot
WIRE
Y
B
O
G
W
RC
RH
THERMOSTAT
SYSTEM
Y
B
O
G
W
RC
RH
Cooling
System Relay System
Fan
Heating
24 VAC
120 VAC
Neutral
Fan
Relay
Heating
System
Hot
HEATING
TRANSFORMER
24 VAC
120 VAC
Neutral
NOTE
For 2-wire Heat only,
attach to RH and W
Hot
TRANSFORMER
24 VAC
120 VAC
Neutral
Figure 2. Typical wiring diagram for
COOLING TRANSFORMER
heat only, 3-wire, single transformer systems
Figure 5. Typical wiring diagram for
heat/cool, 5-wire, two-transformer systems
JUMPER
WIRE
THERMOSTAT
Y
B
O
G
W
RC
RH
SYSTEM
JUMPER
WIRE
JUMPER
WIRE
THERMOSTAT
SYSTEM
Cooling
System Relay
Fan
Y
B
O
G
W
RC RH
Hot
24 VAC
120 VAC
Neutral
Reversing Compressor Fan
Valve*
Contactor Relay
Hot
TRANSFORMER
24 VAC
120 VAC
Neutral
Figure 3. Typical wiring diagram for
cool only, 3-wire, single transformer systems
* Reversing valve is energized when the
system switch is in the COOL position
TRANSFORMER
Figure 6. Typical wiring diagram for heat pump
with reversing valve energized in COOL
NOTE
RED jumper wire (provided with thermostat) must be
connected between thermostat RH and RC terminals
for proper thermostat operation with this system.
JUMPER
WIRE
JUMPER
WIRE
JUMPER
WIRE
THERMOSTAT
SYSTEM
THERMOSTAT
SYSTEM
Y
B
O
G
W
RC RH
Y
B
O
G
W
RC RH
Cooling
System Relay
Fan
Heating
System
Reversing Compressor Fan
Valve*
Contactor Relay
Hot
Hot
24 VAC
120 VAC
Neutral
24 VAC
120 VAC
Neutral
* Reversing valve is energized when the
system switch is in the HEAT position
TRANSFORMER
TRANSFORMER
Figure 7. Typical wiring diagram for heat pump
with reversing valve energized in HEAT
Figure 4. Typical wiring diagram for
heat/cool, 4-wire, single transformer systems
CHECK THERMOSTAT OPERATION
5
This thermostat has a time delay between cooling cycles to allow
the head pressure in the compressor to stabilize. If the tempera-
ture is adjusted to call for cool within 5 minutes of the last cycle the
snowflake icon will blink indicating the thermostat is locked out.
After 3 to 5 minutes, the compressor will start and the snowflake
icon will stop flashing. This helps prevent the compressor from
cycling too quickly and is normal operation for the thermostat.
NOTE
To prevent static discharge problems, touch side of ther-
mostattoreleasestaticbuild-upbeforetouchinganykeys.
If at any time during testing your system does not operate
properly, contact a qualified serviceperson.
Fan Operation
If your system does not have a G terminal connection, skip to
Heating System.
1. Move SYSTEM switch to COOL position.
2. Press
to adjust thermostat setting below room tempera-
ture. The blower should come on immediately on high speed,
followed by cold air circulation
1. Turn on power to the system.
2. Move FAN switch to ON position. The blower should begin to
3. Press
to adjust temperature setting above room tem-
operate.
perature. The cooling system should stop operating.
3. Move FAN switch to AUTO position. The blower should stop
Heating System
immediately.
1. Move SYSTEM switch to HEAT position. If the heating system
Cooling System
has a standing pilot, be sure to light it.
2. Press
to adjust thermostat setting above room tempera-
ture. The heating system should begin to operate.
CAUTION
!
3. Press
to adjust temperature setting below room tem-
To prevent compressor and/or property damage, if the
outdoortemperatureisbelow50°F, DONOToperatethe
cooling system.
perature. The heating system should stop operating.
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CHECK THERMOSTAT OPERATION
CONTINUED FROM THIRD PAGE
5
Before you begin using your thermostat, you should be familiar
with its features and with the display and the location and
operation of the thermostat buttons. Your thermostat consists of
two parts: the thermostat cover and the base. To remove the
cover, gently pull it straight out from the base. To replace the
cover, line up the cover with the base and press gently until the
cover snaps onto the base.
1
2
WHITE-RODGERS
The Thermostat Buttons and Switches
FAN
SYSTEM
1
2
3
4
(Up arrow) Raises temperature setting.
(Down arrow) Lowers temperature setting.
ON AUTO COOL OFF HEAT
FAN switch (ON, AUTO).
3
4
SYSTEM switch (COOL, OFF, HEAT).
The Display
5
is displayed when the SYSTEM switch is in the HEAT
position.
is displayed (non-flashing) when the SYSTEM
is displayed (flashing)
switch is in the COOL position.
6
8
when the compressor is in lockout mode.
6
7
Displays current temperature.
“LO BATTERY” is displayed when the 2 “AAA” batteries are
low and should be replaced. Nothing else will be displayed.
7
5
Displays currently set temperature (this is blank when
8
SYSTEM switch is in the OFF position).
Figure 8. Thermostat display, buttons, and switches
Operating Features
• TEMPERATURE DISPLAY ADJUSTMENT — Your new
thermostat has been accurately set in our factory. However,
if you wish, you may adjust your new thermostat temperature
display to match your old thermostat. This can be accom-
plished (within a ±3° range) as follows:
Now that you are familiar with the thermostat buttons and display,
read the following information to learn about the many features of
the thermostat.
• SIMULTANEOUSHEATING/COOLINGSETPOINTSTOR-
AGE—Youcanenterbothyourheatingandcoolingsetpoints
at the same time. There is no need to re-enter the thermostat
at the beginning of each season.
1. Press
or
at the same time for two seconds with
the SYSTEM switch in OFF position.
• TEMPERATURE SETTING — Press
or
until the
2. Press
or
to adjust the displayed temperature to
display shows the temperature you want. The thermostat will
keep the room temperature at the selected temperature.
your desired setting.
3. Move SYSTEM switch from OFF to exit the feature.
• °F/°C CONVERTIBILITY — The factory default setting is
Fahrenheit. Clipping W904 jumper on the circuit board (see
fig. 1) will alter this feature to Celsius temperature setting.
• DISPLAY BACKLIGHT — (Not available on earlier models.)
The display backlight improves display contrast in low light-
ing conditions. Selecting backlight ON will turn the light on for
a short period of time after any button is pressed. Selecting
backlight OFF (default) will keep the light off. Turn the display
backlight feature ON as follows:
• LOW BATTERY INDICATOR — If the 2 “AAA” alkaline
batteries are low and should be replaced, the display will be
blank except for “LO BATTERY”. When the batteries are low,
pressing any button will cause the display to operate for ten
seconds. After ten seconds, the display will be blank except for
“LOBATTERY”.After“LOBATTERY”hasbeendisplayedfor
4 weeks, the thermostat will raise the temperature 10° above
your setpoint in COOL mode and drop the temperature 10°
below your setpoint in HEAT mode. You cannot program with
low batteries, but you can override setpoint temperature.
1. Press
and
atthesametimefortwosecondswith
the SYSTEM switch in HEAT position. The display will
alternately show “-L” AND “FF” (off).
2. Press
or
to change “FF” to “ON”.
3. Move SYSTEM switch to OFF to exit the feature.
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SPECIFICATIONS
ELECTRICAL DATA
6
7
THERMAL DATA
Electrical Rating:
Setpoint Temperature Range:
45°F to 90°F (7°C to 32°C)
Operating Ambient Temperature Range:
32°F to 105°F
Operating Humidity Range:
0 to 90% RH (non-condensing)
Shipping Temperature Range:
-40°F to 150°F
0 to 30 VAC 50/60 Hz. or D.C.
0.05 to 1.0 Amps (Load per terminal)
1.5 Amps Maximum Total Load (All terminals combined)
TROUBLESHOOTING
Reset Operation
and still does not function correctly contact your heating/cooling
service person or place of purchase.
If a voltage spike or static discharge blanks out the display or
causes erratic thermostat operation you can reset the thermo-
Batteries
stat by pressing
and
at the same time while moving
For optimum performance, we recommend replacing batteries
the SYSTEM switch from OFF to HEAT. This also resets the
factory defaults. If the thermostat has power, has been reset
®
once a year with fresh “AAA” Energizer alkaline batteries.
Symptom
Possible Cause
Corrective Action
No Heat/No Cool/No Fan
(common problems)
1. Blown fuse or tripped circuit breaker.
2. Furnace power switch to OFF.
Replace fuse or reset breaker.
Turn switch to ON.
3. Furnace blower compartment door or
panel loose or not properly installed.
Replace door panel in proper position to engage
safety interlock or door switch.
No Heat
1. Pilot light not lit.
Re-light pilot.
2. SYSTEM Switch not set to HEAT.
Set SYSTEM Switch to HEAT and raise setpoint
temperature above room temperature.
3. Loose connection to thermostat or system.
Verify thermostat and system wires are securely
attached.
4. Furnace Lock-Out Condition. Heat may also
be intermittent.
Many furnaces have safety devices that shut
down when a lock-out condition occurs. If the
heat works intermittently contact the furnace
manufacturer or local service person for
assistance.
5. Heating system requires service or
thermostat requires replacement.
Diagnostic: Set SYSTEM Switch to HEAT and
raise the setpoint above room temperature. Within
a few seconds the thermostat should make a soft
click sound. This sound usually indicates the
thermostat is operating properly. If the thermostat
does not click, try the reset operation listed below.
If the thermostat does not click after being reset
contact your heating and cooling service person
or place of purchase for a replacement. If the
thermostat clicks, contact the furnace manufac
turer or a service person to verify the heating is
operating correctly.
No Cool
1. SYSTEM Switch not set to Cool.
Set SYSTEM Switch to COOL and lower setpoint
temperature below room temperature.
2. Loose connection to thermostat or system.
Verify thermostat and system wires are securely
attached.
3. Cooling system requires service or
thermostat requires replacement.
Same procedure as diagnostic for No Heat
condition except set the thermostat to COOL and
lower the setpoint below the room temperature.
There may be up to a five minute delay before the
thermostat clicks in Cooling.
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TROUBLESHOOTING
CONTINUED FROM FIFTH PAGE
7
Symptom
Possible Cause
Corrective Action
Heat, Cool or Fan Runs Constantly.
1. Possible short in wiring.
Check each wire connection to verify they are not
shorted or touching together. No bare wire should
stick out from under terminal screws. Try resetting
the thermostat as described above If the condition
persists the manufacturer of your system or
2. Possible short in thermostat.
3. Possible short in heat/cool/fan system.
4. FAN Switch set to Fan ON.
service person can instruct you on how to test the
Heat/Cool system for correct operation. If the
system operates correctly, replace the thermostat.
Furnace Cycles Too Fast or Too Slow
(narrow or wide temperature swing)
1. The location of the thermostat and/or the
size of the Heating System may be
influencing the cycle rate.
Digital thermostats normally provide precise
temperature control and may cycle faster than
some older mechanical models. A faster cycle
rate means the unit turns on and off more
frequently but runs for a shorter time so there is
no increase in energy use. If you would like to
increase the cycle time, clip Jumper W-905 as
mentioned in the instructions for Hydronic Heating
Systems. It is not possible to shorten the cycle
time. If an acceptable cycle rate is not achieved as
received or by clipping W-905 contact a local
service person for additional suggestions.
Cooling Cycles Too Fast or Too Slow
(narrow or wide temperature swing)
1. The location of the thermostat and the size
of the Cooling System can influence the
cycle rate.
The cycle rate for cooling is fixed and can not be
adjusted. Contact a local service person for
suggestions.
Thermostat Setting and Thermostat
Thermometer Disagree
1. Thermostat thermometer setting requires
adjustment.
The thermometer can be adjusted +/- 3 degrees.
See Temperature Display Adjustment in the
Operation section.
Blank Display and/or Keypad
Not Responding
1. Voltage spike or static discharge.
2. Battery change required.
Replace batteries and check heat/cool system
for proper operation. If a voltage spike occurs use
the Reset Operation listed above.
The Emerson logo is a
trademark and a service mark
of Emerson Electric Co.
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