Honeywell RTH1120 User Manual
RTH1120
Non-programmable Electronic Thermostat
Installation and User Guide
1. Introduction
The RTH110B non-programmable thermostat can be used to control:
• a gas, fuel oil or electric furnace - 2 or 3 wires
• a central air conditioner - 2 or 3 wires
• a hot water system with or without pump - 2 wires
• a millivolt system - 2 wires
• a central heating and cooling system - 4 or 5 wires
Note: This thermostat is not compatible with heat pumps or multi-
stage systems.
Adjustment
Display
buttons
Backlight
button
q Wrap the wires around a pencil to prevent
them from falling into the wall.
r If the hole in the wall is too big, insulate it
using a non-flammable material in order
to avoid air draughts behind the thermostat.
2.2 Installing the New Baseplate
For a new installation, choose a location approximately 5 feet
(1.5 m) above the floor and on an inside wall. Avoid draughty
areas (top of staircase, air outlet, etc.), dead air spots (behind
doors), direct sunlight or areas near concealed pipes or chimneys.
n Remove the thermostat faceplate.
o Loosen the locking screw to separate the thermostat from its
baseplate (the screw cannot be completely removed).
System operating
mode selector
Features
• System operating mode selection: heat, cool or off
• Fan operating mode selection: automatic or on (continuous)
• Programmable heating and cooling cycle lengths: 10, 12, 15, 20
or 30 minutes
• Temperatur e di sp l ay in °F or °C
• Backlit display
• Battery replacement indicator
• Interchangeable faceplates (titanium, charcoal & taupe)
Fan operating
mode selector
2. Installation
2.1 Removing the Old Thermostat
IN ORDER TO AVOID ANY RISK OF ELECTRIC SHOCK, CUT
POWER TO THE HEATING SYSTEM.
n Remove the old thermostat to access the wires.
Attention: If the old thermostat was mounted onto an electrical box,
it was probably powered by 120/240 volts. In this case, this thermostat cannot be used.
o Identify and label each wire (with the corresponding letter on
the wire terminal) and remove them from the terminals.
p If necessary, strip the end of each wire (maximum of 1/4 inch).
p Tilt the thermostat upwards.
q Mark and bore the appropriate mounting holes (using a 3/16”
drill bit) or use the existing holes. Insert the plastic anchors.
r Pass the wires through the opening of the baseplate and fix the
baseplate to the wall using the screws provided.
2.3 Connecting the Thermostat
Refer to the following table for matching the wire labels with the
thermostat terminals.
RTH2520 terminals Description Wire labels
Rh Heating power supply Rh, R, 4, V
Rc Cooling power supply Rc, R
W Heating signal W, W1, H
Y Cooling signal Y, Y1, M
GFan G, F
Note: Do not connect wires identified as C, X or B. Wrap the bare
end of these wires with electrical tape.
Important: The red jumper wire between Rh and Rc terminals must
be removed in a 5-wire installation.
RTH1120 69-1875EF 22/2/06 1/4
2.3.1 2-wire Heating
2.3.2 2-wire Cooling
2.3.3 3-wire Heating
2.3.4 3-wire Cooling
Heat relay
Cool relay
Heat relay
Cool relay
Fan relay
Fan relay
2.4 Setting J2 Jumper
The jumper specifies how the fan will operate
when it is placed in automatic mode (see section 3.2).
Leave the jumper in this position if you
HG
have a gas or oil heating system.
Move the jumper to this position if you
HE
have an electric heating system.
JP2 jumper
2.5 Installing the Batteries
n Pull out the battery cover.
o Install the batteries as shown. Observe the polarity.
p Reinstall the battery cover. You will hear a clicking sound.
After the batteries are installed, the thermostat performs a series of
tests for approximately 5 seconds.
Afterwards, the screen displays the actual temperature. It is normal that the displayed temperature will
be higher than the ambient temperature if you hold
the thermostat in your hands. It will display the
ambient temperature after the thermostat is
installed on the wall. By default, the setpoint is 70°F (21°C).
2.6 Completing the Installation
2.3.5 4-wire Heating and Cooling
Heat relay
Cool relay
Fan relay
2.3.6 5-wire Heating and Cooling
Fan relay
Heat relay
Note: Remove the red jumper wire between terminals Rc and Rh.
Cool relay
n Once the baseplate and the batteries are installed, mount the
thermostat on the baseplate.
o Secure the thermostat using the locking screw and install the
faceplate.
p Apply power back to the system.
RTH1120 69-1875EF 22/2/06 2/4
3. Basic Functions
3.1 System Operating Mode
Use the selector switch to place the system in Heating
mode (HEAT) or Cooling mode (COOL), or to turn the
system off.
Note: When you place the thermostat in Cooling mode, you might
need to wait up to five minutes before cooling can start. This is a
safety feature for the compressor. will flash on the screen until
cooling can start again.
3.2 Fan Operating Mode
Use the selector switch to set the fan to automatic
mode (AUTO) or continuous mode (ON).
Note: This switch is not used if you have a 2-wire
installation as the fan is not connected to the thermostat.
AUTO
3.3 Displaying the Temperature
The actual temperature is normally displayed. To view the setpoint,
press once on either of the buttons. The setpoint is displayed
for 5 seconds along with the icon.
Note: Pressing any of the buttons more than once will change
the setpoint.
The fan operates only when the heating or cooling system is On (typical setting).
The fan operates continuously. Use this setting to
ON
improve air circulation and air cleaning.
4. Configuration Menu
DISPLAY DESCRIPTION DEFAULT SETTINGS
Temperature
display
Heating cycles
per hour
Cooling cycles
per hour
1
When either the heating or cooling parameter is displayed, use
the system mode selector switch to alternate between the two
parameters.
2
For optimal heating control, use the setting that matches your
system as follows: 2=30 min (steam or gravity), 3=20 min (hot
water or 90%+ high-efficiency furnace),
4=15 min (gas or oil), 5=12 min (alternate setting for gas or oil),
6=10 min (electric).
3
The corresponding cooling cycle lengths are as follows: 2=30
min, 3=20 min, 4=15 min, 5=12 min, 6=10 min.
1
1
n To access the configuration menu, press the backlight button
for 3 seconds.
o To go to the next parameter (menu item), briefly press the back-
light button.
p To modify a parameter, press .
q Repeat steps 2 and 3 if necessary.
r Press the backlight button for 3 seconds to exit the configura-
tion menu.
°F °C or °F
4
4
2, 3, 4, 5 or 6
2, 3, 4, 5 or 6
2
3
3.4 Setting the Temperature
Press one of the buttons until the desired temperature is displayed.
3.5 Backlight
The display illuminates for 12 seconds when the backlight button or
either of the buttons is pressed.
3.6 Battery Replacement Indicator
An icon appears when the batteries need replacement.
This icon will flash for 120 days, then the the rmostat
will cut power to the heating/cooling unit. The icon disappears once the batteries are replaced. The temperature settings are saved and do not need to be re-entered.
Warning: Before removing the batteries, place the
system switch on the thermostat to Off. Otherwise, the
heating/cooling unit might still be running even after
the batteries are removed.
5. Technical Specifications
Power supply: 2 AA batteries
Maximum load: 1 A @ 24 Vac per output
Setpoint range (heating): 41 to 82°F (5 to 28°C)
Setpoint range (cooling): 59 to 95°F (15 to 35°C)
Display range: 23 to 122°F (-5 to 50°C)
Storage temperature: -2 to 122°F (-20 to 50°C)
Temperature display resolution: 1°F (0.5°C)
Accuracy: ± 1°F (0.5°C)
Heating/cooling cycle lengths: 10, 12, 15, 20 or 30 minutes (pro-
grammable)
Compressor short-cycle protection (minimum off time): 5 minutes
Data memory: non-volatile
Dimensions: 5 in. x 3 in. x 1 in. (127 mm x 75 mm x 28 mm)
RTH1120 69-1875EF 22/2/06 3/4
Printed in China
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