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.
After labeling wires, remove wires from terminals.  
6. Mark placement of mounting holes. See Fig. 3.  
Set base aside.  
14. Put the HP/NON HP switch to either the HP for Heat Pump or NON  
HP for furnace applications in the proper position.  
®
Features  
Single Stage heat pump compatible.  
5. Remove existing thermostat base from wall.  
MOUNTING HOLES  
Zone system compatible as a master thermostat.  
Low battery indicator.  
6. Refer to the following section for instructions on how to  
install thermostat.  
HP/NON HP  
Switch  
ELECTRONIC THERMOSTATS  
Fahrenheit/Celsius display option.  
Adjustable from 45(F (4°C) to 90°F (32(C).  
Accuracy within ± 1 degree.  
Installing Model 8334 Thermostat  
NOTE: For new installations, mount thermostat on inside wall, 4-5 feet  
above the floor. Do not install behind a door, in a corner, near air vents,  
in direct sunlight, or near any heat or steam generating fixtures.  
Installation at these places will affect thermostat operation.  
MODEL 8334  
Heat / 1 Cool Digital  
Electric / Gas  
• Adjustable temperature differential: .5 – 1.5 degree.  
Low temperature freeze protection. While in heat mode, thermostat  
will mechanically turn on heat if temperature drops to 40°F (4°C) –  
even if batteries are missing or drained.  
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1. Turn power off to the heating  
and cooling systems.  
Automatic heating shutdown if temperature exceeds 90°F (32°C).  
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. Drill the marked holes using a 3/16" drill bit. NOTE: Enclosed plastic  
15. Install two “AA” ENERGIZER brand batteries or equivalent into bat-  
tery compartment. Be sure to match positive (+) ends of batteries  
with positive (+) battery terminals in the battery compartment.  
2
. Place COOL-OFF-HEAT  
In OFF position.  
Replacing Existing Thermostat  
anchors do not require drilled hole for drywall.  
User’s Manual  
Installation and  
Operation  
8. Tap plastic anchors into the wall.  
1.  
Turn off power to heating and cooling system.  
COOL OFF HEAT  
9. Align base with plastic anchors and feed wires  
through opening.  
2.  
Remove cover of old thermostat to expose wires.  
Do not disconnect wires. (Fig. 1)  
COOL OFF HEAT  
FAN: AUTO - ON  
10. Secure base to wall with supplied screws.  
3.  
Label wires per Table 1.  
11. Connect wires to terminal strip. Refer to wiring diagrams on other  
side of this sheet. Make sure wire connections are secure.  
Table 1  
Old Label  
New Label  
Description  
3
. Place FAN: AUTO-ON switch  
Into AUTO position.  
FAN: AUTO - ON  
12. Place fan option switch into either the "ELEC" or "GAS" position  
depending upon the type of furnace. Refer to Figure 4.  
M, 4, RH, R5 or R  
V or RC  
RH  
Heat Transformer,  
hot side  
RC  
Cooling Transformer,  
hot side  
4. Remove the cover using a coin  
or screwdriver.  
16. Replace cover onto thermostat by snapping into place.  
17. Turn on power to system. Test thermostat as described in  
the following section.  
Y or Y6  
H, W or 4  
F or G  
C*  
Y
Cooling control  
Heating control  
Fan control relay  
ELECTRIC/  
GAS SWITCH  
IMPORTANT SAFETY INFORMATION  
WARNING:  
W
G
Always turn off power at the main power source by unscrewing  
fuse or switching circuit breaker to the off position before installing,  
removing, cleaning, or servicing thermostat.  
Y or None  
Either cooling control  
or common side  
of transformer  
Read all of the information in this manual before installing or  
programming this thermostat.  
O
B
O
B
Cool Active Reversing  
Valve  
Figure 2  
This is a 24V AC low-voltage thermostat. Do not install on voltages  
higher than 30V AC.  
Heat Active Reversing  
Valve  
figure 4  
All wiring must conform to local and national building and electrical  
codes and ordinances.  
*
NOTE: On some older models, the C terminal can be either the cooling  
5. Place thermostat against the wall at desired location. Make sure  
wires will feed through opening on base of thermostat.  
13. Put the °F/°C switch to either °F for Fahrenheit display  
or °C for Celsius display readout.  
control or the common side of the transformer. Check furnace wiring  
diagram to verify C terminal. If it is the common side of the transformer,  
cap the wire and tuck into the wall.  
Do not short (jumper) across terminals on the gas valve or at the  
system control to test installation. This will damage the thermostat  
and void the warranty.  
°
F/°C  
If it is the cooling control, connect  
to the Y terminal.  
F°/°C  
SWITCH  
Switch  
Figure 1  
1
2
3
4
5
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To Test Thermostat  
Operation  
Setting or Changing the Setpoint Temperature  
Changing Fahrenheit (F) to Celsius (C)  
The thermostat is preset to display the temperature in degrees  
Fahrenheit. You may change the display readout to Celsius if desired.  
Wiring Diagrams  
The following is just a sample of the most common types of HVAC systems.  
Refer to your systems installation manual for wiring information.  
Limited Warranty  
®
WARNING: DO NOT SHORT (JUMPER) ACROSS TERMINALS OF GAS  
VALVE OR SYSTEM CONTROL TO TEST OPERATION. THIS WILL DAMAGE  
THE THERMOSTAT AND VOID YOUR WARRANTY.  
Your Research Products Corporation Aprilaire Thermostat unit is expressly  
1. Press either the  
The display will show the current  
temperature setpoint.  
or  
button.  
warranted for two (2) years from date of installation to be free from defects in  
materials and workmanship.  
1. Move the manual switch marked “F” (Fahrenheit) and “C” (Celsius)  
located at the top center of the circuit board to the desired setting.  
CAUTION: Do not switch system to cool if the temperature is below  
HEAT  
/
COOL  
HEAT ONLY  
3-WIRE  
Research Products Corporation’s exclusive obligation under this warranty  
shall be to supply, without charge, a replacement for any thermostat which is  
found to be defective within a two (2) year period and which is returned,  
together with the date of installation, no later than thirty (30) days after said  
two (2) year period by you to either your original supplier or to Research  
Products Corporation, Madison, Wisconsin 53701.  
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0°F (10°C). This can damage the air conditioning system and cause  
2. Press RESET button located lust below the LCD display to register  
the change.  
4-WIRE  
SINGLE TRANSFORMER  
SINGLE TRANSFORMER  
personal injury.  
Factory-Installed  
jumper  
Factory- Installed  
jumper  
The display will change to show the temperature in your desired  
temperature scale. To return the thermostat to its original setting,  
repeat steps 1 and 2 above.  
1. Place the COOL-OFF-HEAT switch  
into the COOL position  
COOL OFF HEAT  
T
T
RH  
RH  
Transformer  
Hot  
H
E
R
M
O
S
T
Transformer  
Hot  
H
E
R
M
O
S
T
COOL OFF HEAT  
FAN: AUTO - ON  
RC  
W
RC  
W
1
20 VAC  
24 VAC  
120 VAC  
24 VAC  
2
. Press the  
button until the  
Heating  
Control  
Heating  
Control  
temperature setting is at least  
THIS WARRANTY SHALL NOT OBLIGATE RESEARCH PRODUCTS CORPO-  
RATION FOR ANY LABOR COSTS AND SHALL NOT APPLY TO DEFECTS IN  
WORKMANSHIP OR MATERIALS FURNISHED BY YOUR INSTALLER AS  
CONTRASTED TO DEFECTS IN THE THERMOSTAT ITSELF.  
Cooling  
Control  
Y
Y
3
degrees below the room temperature.  
A
T
Fan  
Control  
A
T
The air conditioning system should  
turn on within a few seconds.  
2. Press either the  
to adjust the temperature setting  
either up or down.  
or  
button  
Fan  
Control  
G
G
TROUBLESHOOTING  
Symptom  
Remedy  
NOTE: When in the COOL mode (or HEAT and COOL for single stage  
heat pumps), once the thermostat turns off, a built in 5-minute delay  
prevents the system from turning on again. This protects the compressor.  
No additional time delay relay is required.  
HEAT ONLY  
2-WIRE  
SINGLE TRANSFORMER  
The display will return to the room temperature display five seconds after  
the last input and the new setpoint will be saved.  
IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PAR-  
TICULAR PURPOSE SHALL BE LIMITED IN DURATION TO THE AFORESAID  
TWO YEAR PERIOD. RESEARCH PRODUCTS CORPORATION’S LIABILITY  
FOR INCIDENTAL OR CONSEQUENTIAL DAMAGES, OTHER THAN DAMAGES  
FOR PERSONAL INJURIES, RESULTING FROM ANY BREACH OF THE AFORE-  
SAID IMPLIED WARRANTIES OR THE ABOVE LIMITED WARRANTY IS  
EXPRESSLY EXCLUDED. THIS LIMITED WARRANTY IS VOID IF DEFECT(S)  
RESULT FROM FAILURE TO HAVE THIS THERMOSTAT INSTALLED BY A  
QUALIFIED HEATING AND AIR CONDITIONING CONTRACTOR. IF THE  
LIMITED WARRANTY IS VOID DUE TO FAILURE TO USE A QUALIFIED  
CONTRACTOR, ALL DISCLAIMERS OF IMPLIED WARRANTIES SHALL BE  
EFFECTIVE UPON INSTALLATION.  
Thermostat does not turn  
on system  
Check Wiring  
(see INSTALLATION).  
COOL ONLY  
3-WIRE  
SINGLE TRANSFORMER  
NOTE: Remove factory  
installed jumper  
Check fuse. Replace with 2 amp  
fuse if fuse has opened.  
T
RH  
T
H
Transformer  
Hot  
H
E
R
M
O
S
T
RH  
COOL OFF HEAT  
Changing Temperature Differential  
IMPORTANT: The temperature differential is factory set at 1 (.5°). This  
means that whenever the room temperature changes by one half of a  
degree from the temperature setting, the system will turn on. If the  
system turns on too often, increase the temperature differential.  
Transformer  
3
. Put the COOL-OFF-HEAT switch  
RC  
W
Hot  
RC  
W
E
R
M
O
S
T
1
20 VAC  
24 VAC  
Heating  
Control  
120 VAC  
24 VAC  
into the OFF position. The air  
Thermostat turns on and  
off too frequently.  
Increase Temperature Differential  
(see DIFFERENTIAL).  
conditioning system should turn off.  
Y
Cooling  
Control  
Y
4. Put the COOL-OFF-HEAT switch  
into the HEAT position.  
A
T
Fan  
Control  
A
T
COOL OFF HEAT  
Display is blank, flashing  
or constant “LO BAT”.  
Replace batteries.  
G
G
1
. Press both  
at the same time and hold for one  
second.  
and  
buttons  
5
. Press the  
temperature setting is at least  
degrees above room temperature.  
button until the  
HEAT  
5-WIRE  
TWO TRANSFORMER  
/COOL  
System fan does not  
operate properly.  
Move fan option switch to either  
gas or electric, to match system  
(see INSTALLATION).  
3
(
HEATING)  
NOTE: Cut center of  
Transformer  
Hot  
factory installed jumper  
and bend back  
The heating system should turn on.  
The fan may not turn on immediately,  
depending upon the fan delay built  
into the furnace.  
Some states do not allow limitations on how long an implied warranty lasts or  
the exclusion or limitation of incidental or consequential damages, so the  
above exclusion or limitations may not apply to you.  
T
H
E
R
M
O
S
T
RH  
RC  
120 VAC  
24 VAC  
NOTE: Both transformers  
must be in phase.  
Thermostat does not display  
proper room temperature.  
Check “F” Fahrenheit/”C” Celsius  
switch located at top center of  
circuit board for proper position.  
If a new selection is made, press  
Heating  
Control  
W
Y
COOL OFF HEAT  
FAN: AUTO  
-
ON  
Cooling  
Control  
This warranty gives you specific legal rights and you may also have other  
rights which vary from state to state.  
6
. Put the COOL-OFF-HEAT switch  
into the OFF position. The heating  
system should turn off. The fan may  
continue to run for a short period  
of time.  
COOL OFF HEAT  
Hot  
120 VAC  
24 VAC  
Fan  
Control  
A
T
RESET” button located directly  
G
(COOLING)  
Transformer  
below LCD display.  
2. Press either the  
or  
button  
to adjust the temperature  
differential up or down.  
FAN: AUTO - ON  
FAN: AUTO - ON  
7
. Put the FAN: AUTO-ON switch to  
the ON position. The blower fan  
should turn on.  
HEAT PUMP WITH  
COOL ACTIVE  
REVERSING VALVE  
HEAT PUMP WITH  
HEAT ACTIVE  
REVERSING VALVE  
If problems with thermostat cannot be solved, call:  
The display will show:  
Technical Support: 608-257-8801  
Monday-Friday 7:45 am-5:00 pm CST  
Pre-Installed jumper  
Pre-Installed jumper  
8
. Put the FAN: AUTO-ON switch to  
the AUTO position. The blower fan  
should turn off.  
RH  
RC  
RH  
RC  
T
H
E
R
M
O
S
T
T
H
E
R
M
O
S
T
Differential  
Setting Degrees  
Transformer  
Hot  
Transformer  
Hot  
1
20 VAC  
24 VAC  
120 VAC  
24 VAC  
W
W
G
1
2
3
1°F/.5°C  
2°F/1.0°C  
3°F/1.5°C  
Fan  
Relay  
Fan  
Relay  
G
Y
Compressor  
Contactor  
Compressor  
Contactor  
Y
A
T
A
T
Reversing  
Valve  
O
B
O
B
Re Vv ae lr vs ei ng  
The display will return to the room temperature  
five seconds after the last input.  
NOTE: Installer must place jumper  
between “W” and “Y” terminals.  
NOTE: Installer must place jumper  
between “W” and “Y” terminals.  
P.O. BOX 1467 • MADISON, WI 53701-1467  
Products For Better Indoor Air Quality  
B2202515 REV. 12/00  
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