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Electronic/Mechanical  
Thermostat  
installation and  
operation manual  
Model 40120  
1
44018-01 04-01-2008  
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For assistance with wiring or operation, our Technical  
Support Group is available from 8 am to 5 pm CST.  
they may be reached toll-free at 1-888-830-1326.  
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Table of Contents  
Important Information .......................................5  
Tools.................................................................6  
Uninstalling the Existing Unit............................ 9  
Installing the Thermostat ................................12  
Installing the wall plate ...................................14  
connecting the wires...........................15  
attaching the thermostat ..................... 17  
Operation........................................................20  
Indicators & Adjustments................................22  
Troubleshooting..............................................25  
Wiring Diagrams.............................................27  
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Electronic/Mechanical  
Thermostat  
Model 40120  
Congratulations!  
Thank you for choosing a Hunter thermostat.  
Your new Hunter thermostat will provide years of  
reliable service and year-round energy savings.  
Please read this manual before beginning  
installation and save this booklet for complete  
operation instructions.  
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IMPOꢀTAꢁT IꢁFOꢀMATIOꢁ  
This thermostat is designed to work on the following  
heating and cooling systems:  
Gas – Standing Pilot  
Gas – Electronic Ignition  
Gas – Fired Boilers  
Gas – Millivolt Systems  
Oil – Fired Boilers  
Oil – Fired Furnace  
Electric Furnace  
This thermostat is not designed for heat pump  
systems or 110/220 V baseboard heating systems.  
If you are unsure what kind of heating and cooling  
system you have, please contact a qualified HVAC  
Technician for assistance.  
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TOOꢂS  
This thermostat includes two #8 slotted screws and  
two wall anchors for mounting.  
To install your new thermostat, you will need the  
following supplies:  
Flat-head screwdriver  
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Small Phillips-head screwdriver  
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Hammer  
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Electric drill and 3/16” bit  
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Two fresh 1.5 Volt (AA) size alkaline batteries  
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ꢁOTICE! Do not disconnect the wires  
from the existing thermostat before  
reading these instructions. The wires  
must be labeled prior to removal to  
ensure proper reconnection.  
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UꢁIꢁSTAꢂꢂIꢁG THE EꢃISTIꢁG UꢁIT  
1
. Turn the system power OFF from the existing  
thermostat. Turn the power to the HVAC  
system OFF at the main power panel or at the  
furnace.  
2. ꢀemove the existing thermostat cover to  
access the wires from the wall.  
(Some thermostats may have multiple covers, screws  
or other locking devices that must be removed or  
disengaged.)  
3
. ꢂocate, but do not disconnect the wires.  
(If wires are not visible, they may be connected to the  
back of the wall plate. Some models may have doors  
that open to expose the wires and mounting screws.)  
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If your existing  
thermostat is marked...  
label the wire  
with this sticker:  
H ꢀ  
ꢀH / ꢀ / Vꢀ / 4  
24 Volt  
ꢀH  
W
W / H  
heating  
fan  
W
G
G / F  
G
*
See page 27 for complete wiring diagram.  
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UꢁIꢁSTAꢂꢂIꢁG THE EꢃISTIꢁG UꢁIT, COꢁT.  
4
. Using the provided stickers, label each wire  
according to the chart.  
(If the terminals are not labeled, contact a  
qualified HVAC technician.)  
ꢁ
ote: Wire colors do not always comply with  
standards, so wire color should be ignored.  
efer to the existing terminal designation for  
ꢀ
proper identification.  
*
If a wire marked C is present, C may be a  
Common wire and should not be used. If you have  
a wire marked C, do not connect it to any terminal.  
This wire is used only for non-battery powered  
thermostats.  
5
. Do not let the wires slip back into the wall  
during disconnection. You may want to secure  
the wires to the wall as you disconnect them.  
After all wires are labeled, disconnect each  
wire and remove the existing wall plate.  
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IꢁSTAꢂꢂIꢁG THE THEꢀMOSTAT  
IꢁSTAꢂꢂIꢁG THE THEꢀMOSTAT  
1
. ꢀemove the new thermostat from the back  
plate by pulling the two halves apart.  
Wall Plate  
Thermostat  
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13  
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IꢁSTAꢂꢂIꢁG THE THEꢀMOSTAT, COꢁT.  
IꢁSTAꢂꢂIꢁG THE WAꢂꢂ PꢂATE  
2. Position the new wall plate on the wall and pull  
the labeled wires through the opening.  
3
. If the existing holes do not match those on the  
Hunter wall plate, or if there are no existing  
holes, level the wall plate and mark the wall for  
two holes.  
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5
6
. ꢀemove the wall plate and drill two 3/16” holes  
where marked.  
. Tap the plastic anchors into the holes until they  
are flush with the wall.  
. ꢀeposition the wall plate on the wall, pulling the  
wires through the opening. Insert the mounting  
screws through the mounting holes and into the  
anchors. Verify that the thermostat is visually  
level and securely tighten both screws.  
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G
RH  
W
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IꢁSTAꢂꢂIꢁG THE THEꢀMOSTAT, COꢁT.  
COꢁꢁECTIꢁG THE WIꢀES  
1. ꢂoosen, but do not remove, the terminal  
screws.  
2
. Match and connect the wires from the wall  
to the terminals as shown. Wires should be  
inserted behind the black terminal shields.  
Tighten each screw after the connection has  
been made.  
(The ends of any extra wires should be wrapped in  
electrical tape and carefully pushed back into the wall.)  
3
. Push any excess wire length back into the wall  
to prevent interference.  
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HE/HG Switch  
HG  
HE  
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IꢁSTAꢂꢂIꢁG THE THEꢀMOSTAT, COꢁT.  
ATTACHIꢁG THE THEꢀMOSTAT  
4
. ꢂocate the HE/HG s w it c H on the back of the  
thermostat. Set the switch to HG for a gas  
furnace or oil burner. Set the switch to HE for  
electric furnaces.  
5. Insert two fresh AA alkaline batteries.  
6. Align the thermostat with the the wall plate,  
and snap the two halves together.  
7
. ꢀestore power at the electrical panel or  
furnace.  
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19  
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Thermometer Set Temperature  
Slider  
System  
Switch  
SYSTEM  
OFF  
HEAT  
9
0
0
90  
30  
20  
8
80  
70  
70  
6
50  
F
0
6
0
AUTO  
ON  
10  
C
50  
F
Fan  
Battery Indicator  
Switch  
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OPEꢀATIOꢁ  
1
2
3
. Set the sE t tE m p E r a t u r E s l id E r to the desired  
temperature.  
. The sy s t E m sw it c H determines the operating  
mode of the thermostat. Select Of f or HE a t .  
. The fa n sw it c H should normally be located in  
the au t O position. To run the fan continuously,  
slide the fa n sw it c H to the On position.  
ꢁ
ote: In au t O , The fan will be turned on along with normal  
operation of your system. In a normal gas or oil furnace, the  
fan will be turned on by your furnace after its warm-up delay.  
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IꢁDICATOꢀS AꢁD ADUSTMEꢁT  
1
. The tH E r m O m E t E r indicates the room  
temperature.  
2
. The Ba t t E r y in d ic a t O r displays two stages of  
wE a k Ba t t E r y wa r n in G , indicated by the Ba t t E r y  
in d ic a t O r flashing once approximately every  
second. When this warning appears, install  
two fresh AA alkaline batteries at your earliest  
convenience.  
3
. The second warning is the sH u t -d O w n in d ic a t O r ,  
indicated by the Ba t t E r y in d ic a t O r flashing  
approximately twice every second. When this  
warning appears, the thermostat is shut down  
and will turn your system OFF. Your system  
will remain shut-off until you install two fresh  
AA alkaline batteries.  
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Span Adjust SPAN  
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IꢁDICATOꢀS AꢁD ADꢄUSTMEꢁTS, COꢁT.  
Your thermostat is preset to cycle your system  
o
off and on at 1 F above and below the Set  
Temperature. For maximum system efficiency and  
a sustained comfortable temperature your system  
should cycle 3 - 5 times per hour. If your system is  
cycling either too often or not often enough, then  
use a small Phillips-head screwdriver to turn the  
sp a n ad j u s t left or right to change the cycle time.  
1. ꢀemove the thermostat from the wall plate.  
2
. To make your system run ꢂOꢁGEꢀ, turn the  
sp a n ad j u s t clockwise.  
3
. To make your system run SHOꢀTEꢀ, turn the  
sp a n ad j u s t counter clockwise.  
4. ꢀeattach the thermostat to the wall plate.  
o o  
ꢁ
ote: The Span range is 0.6 F - 3 F. The Span setting remains  
the same in both the Heat and Cool modes and can be  
changed regardless of what position the System Switch is in.  
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1. My heating or cooling will not turn on or off.  
1
1
a. Check the HE/HG switch to ensure it is set to the correct  
position.  
b. Check the circuit breakers and switches to ensure there is  
enough power to the system.  
1
1
c. ꢀeplace the batteries with fresh AA alkaline batteries.  
d. If applicable, make sure the furnace blower door is closed  
properly.  
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2. My system continues to operate when the  
thermostat is in the off position.  
2
a. ꢀeplace unit.  
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TꢀOUBꢂESHOOTIꢁG  
Is there help on the web?  
Yes. Visit http://www.hunterfan.com for more information.  
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Can’t I just call someone?  
Sure. Our Technical Support Group is available from 8 am  
to 5 pm CST. They may be reached toll-free at1-888-830-  
1326.  
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WIꢀIꢁG DIAGꢀAMS  
2-wire Heat Only System  
Rh  
W
Heat 24V or  
Millivolt Supply  
Heat Relay  
or Valve  
3-wire Heat Only System  
G
Rh  
W
Fan  
Relay  
Heat 24V  
Supply  
Heat Relay  
or Valve  
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8 © 2007 Hunter Fan Company  
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