Honeywell RTH110B Non-Programmable electronic Thermostat



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 multistage systems.image 1
  • 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
  • Temperature display in °F or °C
  • Battery replacement indicator


Removing the Old Thermostat

  1. 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.
  2. Identify and label each wire (with the corresponding letter on the wire terminal) and remove them from the terminals.
  3. If necessary, strip the end of each wire (maximum of 1/4 inch).
    This is a legacy product document supported by Resideo. It is no longer manufactured.
  4. Wrap the wires around a pencil to prevent them from falling into the wall.
  5. 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.image 2
Installing the New Baseplate
image 2

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.

  1. Remove the thermostat faceplate.
  2. Loosen the locking screw to separate the thermostat from its baseplate (the screw cannot be completely removed).image 3
  3. Tilt the thermostat upwards.
  4. Mark and bore the appropriate mounting holes (or use the existing holes). Insert the plastic anchors.
  5. Pass the wires through the opening of the baseplate and fix the baseplate to the wall using the screws provided.
Connecting the Thermostat

The connection of the new thermostat should be similar to that of the old thermostat; however, it can vary depending on the installation.

RhHeating power supply
RcCooling power supply
WHeating signal
YCooling signal
image 4
image 5

Note: The red jumper wire between the Rc and Rh terminals must be removed in 2- or 5-wire installations. The jumper must be used in 3- or 4-wire installations if you wish to use the mode selector switch for the fan.

Setting J2 Jumper

image 6

The jumper defines the fan operation when the fan is placed in automatic mode.

Installing the Batteriesimage 7
  1. Pull out the battery cover.
  2. Install the batteries as shown. Observe the polarity.
  3. 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).
Completing the Installation
image 8
  1. Once the baseplate and the batteries are installed, mount the thermostat on the baseplate.
  2. Secure the thermostat using the locking screw and install the faceplate.
  3. Apply power back to the system.

Basic Functions

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.

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•      If you have an electric furnace (see section 2.4), the fan works only when heating or cooling is activated.•      If you have a gas or fuel oil furnace (see section 2.4), the fan works as follows:•       When the thermostat is placed in cool mode, the fan works only when cooling is activated.•       When the thermostat is placed in heat mode, the fan is con- trolled by the furnace fan control circuitry.
ONThe fan is always on.

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.

Setting the Temperature
Press one of the buttons until the desired temperature is displayed.

Battery Replacement Indicator

An icon appears when the batteries need replacement. This icon will flash for 120 days, then the thermostat 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.

Configuration Menu

  1. To access the configuration menu, press both buttons simultaneously for 3 seconds.
  2. To go to the next parameter (menu item), briefly press both buttons simultaneously.
  3. To modify a parameter, press one of the buttons.
  4. Repeat steps 2 and 3 if necessary.
  5. Press both buttons simultaneously for 3 seconds to exit the configuration menu.
    DISPLAYDESCRIPTIONDEFAULTSETTINGSTemperature display°F°C or °FHeating cycles per hour 142, 3, 4, 5 or 6 2Cooling cycles per hour 142, 3, 4, 5 or 6 31 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.

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 (programmable)
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)


Honeywell warrants this product, excluding battery, to be free from defects in the workmanship or materials, under normal use and service, for a period of one (1) year from the date of purchase by the consumer. If at any time during the warranty period the product is determined to be defective or malfunctions, Honeywell shall repair or replace it (at Honeywell’s option).
If the product is defective,

  1. return it, with a bill of sale or other dated proof of purchase, to the place from which you purchased it, or
  2. call Honeywell Customer Care at 1-800-468-1502. Customer Care will make the determination whether the product should be returned to the following address: Honeywell Return Goods, Dock 4 MN10-3860, 1885 Douglas Dr N, Golden Valley, MN 55422, or whether a replacement product can be sent to you.

This warranty does not cover removal or reinstallation costs. This warranty shall not apply if it is shown by Honeywell that the defect or malfunction was caused by damage which occurred while the product was in the possession of a consumer.

Honeywell’s sole responsibility shall be to repair or replace the product within the terms stated above. HONEYWELL SHALL NOT BE LIABLE FOR ANY LOSS OR DAMAGE OF ANY KIND, INCLUDING ANY INCIDENTAL OR CONSEQUENTIAL DAMAGES RESULTING, DIRECTLY OR INDIRECTLY, FROM ANY BREACH OF ANY WARRANTY, EXPRESS OR IMPLIED, OR ANY OTHER FAILURE OF THIS PRODUCT. Some states do not allow the exclusion or limitation of incidental or consequential damages, so this limitation may not apply to you. THIS WARRANTY IS THE ONLY EXPRESS WARRANTY HONEYWELL MAKES ON THIS PRODUCT. THE DURATION OF ANY IMPLIED WARRANTIES, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, IS HEREBY LIMITED TO THE ONE-YEAR DURATION OF THIS WARRANTY. Some states do not allow limitations on how long an implied warranty lasts, so the above limitation may not apply to you. This warranty gives you specific legal rights, and you may have other rights which vary from state to state.
If you have any questions concerning this warranty, please write Honeywell Customer Relations, 1985 Douglas Dr, Golden Valley, MN 55422 or call 1-800-468-1502. In Canada, write Retail Products ON15-02H, Honeywell Limited/Honeywell Limitée, 35 Dynamic Drive, Scarborough, Ontario M1V4Z9.

Customer Assistance


If you have any questions about the operation of your thermostat, please go to www.honeywell.com/yourhome, or call Honeywell Customer Care toll-free at 1-800-468-1502.

Documents / Resources

Honeywell RTH110B Non-Programmable electronic Thermostat [pdf] Installation Guide
RTH110B, Non-Programmable electronic Thermostat


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