Honeywell RTH2520 Programmable Thermostat Installation Guide

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Honeywell RTH2520 Programmable Thermostat



The RTH2520 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.

Honeywell RTH2520 Programmable Thermostat -FIG.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
  • Backlit display
  • Battery replacement indicator
  • 7-day programming including:
    • Preprogrammed energy-saving schedule
    • Early Start
    • Temporary bypass
    • Time display (12 h or 24 h)
  • Filter replacement indicator
  • Automatic daylight savings changeover
  • Interchangeable faceplates (titanium, charcoal & taupe)


Removing the Old Thermostat

  1. Remove the old thermostat to access the wires.
    Warning: 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).
  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 to avoid air draughts behind the thermostat.

Honeywell RTH2520 Programmable -Identify

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 the staircase, air outlet, etc.), dead air spots (behind doors), direct sunlight, or areas near concealed pipes or chimneys.

  1. Remove the thermostat faceplate.
    Honeywell RTH2520 Programmable - areas
  2. Loosen the locking screw in order to separate the thermostat from its baseplate (the screw cannot be completely removed).
    Honeywell RTH2520 Programmable - tu
  3. Gently tilt the thermostat upwards.Honeywell RTH2520 Programmable - Gently
  4. Mark and bore the appropriate mounting holes (using a 3/16” drill bit) or use the existing holes. Insert the plastic anchors.
    Honeywell RTH2520 Programmable - Mark
  5. Pass the wires through the opening of the baseplate and fix the baseplate to the wall using the screws provided.

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, Wl, H
Y Cooling signal Y, Yl, M
G Fan 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.

2.3.1 2-wire Heating Honeywell RTH2520 Programmable - uji
2.3.2 2-wire Cooling Honeywell RTH2520 Programmable - Cooling
2.3.3 3-wire Heating Honeywell RTH2520 Programmable - Heating
2.3.4 3-wire Cooling Honeywell RTH2520 Programmable - -wire Cooling
2.3.5 4-wire Heating and Cooling Honeywell RTH2520 Programmable - e Heating and Cooling
2.3.6 5-wire Heating and Cooling Honeywell RTH2520 Programmable - e Heating and

Note: Remove the red jumper wire between terminals Rc and Rh.

Setting JP2 Jumper
The jumper specifies how the fan will operate when it is placed in automatic mode (see section 3.2).

Honeywell RTH2520 Programmable - JP2 jumper

HG Leave the jumper in this position if you have a gas or oil heating system.
HE Move the jumper to this position if you have an electric heating system.

Installing the Batteries

Honeywell RTH2520 Programmable - Batteries Honeywell RTH2520 Programmable - e battery cover
  1.  Gently 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 the sequence of tests for approximately 5 seconds.
Afterwards, the screen displays the actual temperature. It is normal that the displayed temperature be higher than the ambient temperature if you are holding the thermostat. Once installed on the wall, the thermostat will display the ambient temperature. By default, the setpoint is 70°F (21°C).
The time and day settings flash to indicate that they must be set (see section 5.1).

Honeywell RTH2520 Programmable - holding

Completing the Installation

Honeywell RTH2520 Programmable - e baseplatev Honeywell RTH2520 Programmable - mount the
  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 this selector switch to place the system in Heating mode (HEAT) or Cooling mode (COOL), or to set both modes to Off.

Honeywell RTH2520 Programmable - time
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 during the delay.

Fan Operating Mode

Use the selector switch to set the fan to automatic mode (AUTO) or continuous mode (ON).

Honeywell RTH2520 Programmable - time
Note: This switch is not used in a 2-wire installation as the fan is not connected to the thermostat in this type of installation.

AUTO The fan operates only when the heating or cooling system is
On (typical setting).
ON The fan operates continuously. Use this setting to improve air circulation and air cleaning.

Displaying the Temperature
The actual temperature is normally displayed. To view the setpoint, press once on one of theHoneywell RTH2520 Programmable - icon buttons. The setpoint is displayed for 5 seconds along with the icon.
Note: Pressing either of theHoneywell RTH2520 Programmable - icon buttons more than once will change the setpoint.
Setting the Temperature
Press one of theHoneywell RTH2520 Programmable - icon buttons until the desired temperature is displayed.
The display illuminates for 12 seconds when the backlight Honeywell RTH2520 Programmable - iconbutton or either of the buttons is pressed.

Thermostat Control Mode

  1. Manual/Permanent Hold Mode
    Maintains the temperature at a fixed setpoint. To place the thermostat in this mode, press [ Mode ]. The house icon will disappear.
  2. Programmable Mode
    Maintains the temperature according to the energy-saving schedule. To place the thermostat in this mode, press [ Mode ]. The current period will be displayed. The four possible periods are:

Honeywell RTH2520 Programmable - 1

Temporary Bypass
If you modify the setpoint (using theHoneywell RTH2520 Programmable - icon buttons) when the thermostat is in Programmable mode, the thermostat will use the new setpoint for the next 2 hours.
The house icon flashes during the bypass. Afterwards, the thermostat will return to the temperature setting of the period currently underway.

Filter Replacement IndicatorHoneywell RTH2520 Programmable - Cooling
After 500 hours of operation, an icon appears to indicate that the filter needs replacement. Once the filter is replaced, press [Filter] for 3 seconds to remove the
icon and reset the counter.

Battery Replacement IndicatorHoneywell RTH2520 Programmable - bettay
Install fresh batteries immediately when the icon starts flashing. The icon flashes for 120 days before the batteries are depleted. You should replace batteries once a year or before leaving home for more than a month even if the icon has not appeared.
After replacing the batteries, set the time, day, and date (see sections 5.1 and 5.2). However, the temperature and program settings are saved and do not need to be re-entered.Honeywell RTH2520 Programmable - time 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

Temperature display °F °C or °F
Time display 12 h 12 h or 24 h
Early start¹ Off On or Off
Automatic daylight savings changeove² Off On or Off
Heating cycles per hour³ 4 2, 3, 4, 5 or 6 4
 Cooling cycles per hour³ 4 2, 3, 4, 5 or 6 5
  1. When Early Start is On, the thermostat determines when to start heating or cooling so that the desired temperature is reached at the set time.
  2. When this function is On, the thermostat automatically switches to daylight savings time on the second Sunday of March and to normal time on the first Sunday of
    November (see section 5.2).
  3. Use the Heat/Cool selector switch to switch between the heating parameter and the cooling parameter.
  4. For optimal heating control, use the setting that matches your system as follows:2=30 min (steam, gravity), 3=20 min (hot water, 90%+ high-efficiency furnace), 4=15 min (gas or oil), 5=12 min (the alternate setting for gas or oil), 6=10 min (electric).
  5. The corresponding cooling cycle lengths are 2=30 min., 3=20 min., 4=15 min., 5=12 min., 6=10 min.
  1. To access the configuration menu, press the backlight button for 3 seconds.
  2. To go to the next parameter (menu item), briefly press the backlight button.
  3. To modify a parameter, press.
  4. Repeat steps 2 and 3 if necessary.
  5. Press the backlight button for 3 seconds to exit the configuration menu.


Honeywell RTH2520 Programmable - Time and Day

Setting the Time and Day

  1. Press [ Clk ]. The hour flashes.
  2. Set the hour usingHoneywell RTH2520 Programmable - icon.
  3. Press [ Clk ]. The minutes flash.
  4. Set the minutes usingHoneywell RTH2520 Programmable - icon.
  5. Press [ Clk ]. The day flashes.
  6. Set the day usingHoneywell RTH2520 Programmable - icon. (MO: Monday, TU: Tuesday, WE: Wednesday, TH: Thursday, FR: Friday, SA: Saturday and SU: Sunday).
  7. Press [ Exit ] to exit.

Setting the Date
The date is needed for automatic daylight savings changeover.

  1. Press [ Clk ] for 3 seconds to display the year.
    Honeywell RTH2520 Programmable - the year
  2. Set the year usingHoneywell RTH2520 Programmable - icon and press [ Clk ] to display the month.
    Honeywell RTH2520 Programmable - tine1
  3. Set the month usingHoneywell RTH2520 Programmable - icon and press [ Clk ] to display the date.
    Honeywell RTH2520 Programmable - time 2
  4. Set the date usingHoneywell RTH2520 Programmable - icon.
  5. Press [ Exit ] to exit.

Energy-saving Schedule
Your thermostat is preprogrammed with an energy-saving schedule. The schedule automatically controls your heating or cooling system by switching from one set point to the next according to the present times.

Default program settings MO TU WE TH FR SA SU
Honeywell RTH2520 Programmable - sorjo Heating 70°F (21°C) 6:00 a.m.
Cooling 78°F (25.5°C)
Honeywell RTH2520 Programmable - Heating Heating 62°F (16.5°C) 8:00 a.m
Cooling 85°F (29.5°C)
Honeywell RTH2520 Programmable - Return home Heating 70°F (21°C) 6:00 p.m.
Cooling 78°F (25.5°C)
Honeywell RTH2520 Programmable - Sleepv Heating 62°F (16.5°C) 10.00 p.m.
Cooling 82°F (28°C)

Modifying the Schedule
You can program up to 4 periods per day, each period having its own temperature settings. You can have a different program for each day of the week. For each period, you can set the start time, the heating setpoint, and the cooling setpoint.
Note: If you wish to use only 2 periods, set periods “1 and 4” or periods “2 and 3”. Early Start will not work if you set periods “1 and 2” or periods “3 and 4”.

  1.  Press [ Pgm ]. The period 1 setting is displayed.
    Honeywell RTH2520 Programmable - start time
    Note: During programming, to skip a period, press [ CLR ] while the period is displayed. For example, in the predefined energy-saving schedule, periods 2 and 3 have been skipped for Saturday and Sunday.
  2. Press [ Day ] to select the day. Press for 3 seconds to select all 7 days. (MO: Monday,
    TU: Tuesday, WE: Wednesday, TH: Thursday, FR: Friday, SA: Saturday, and SU: Sunday).
  3. Set the time (in increments of 15 minutes) using the buttons.
  4. Press [ P# ]. The heating or cooling setpoint flashes depending on the position of the Heat/ Cool selector.
    Honeywell RTH2520 Programmable - time
  5. Set the desired temperature for the displayed period using theHoneywell RTH2520 Programmable - icon buttons.
  6. Use the Heat/Cool selector to switch to the other mode (e.g., if you were in Heating mode, switch to Cooling mode). The setpoint for that mode flashes.
  7. Set the desired temperature using the buttons.
  8. Press [ P# ] to go to the next period.
  9. Repeat steps 2 to 8 for the remaining periods.
  10. Press [ Exit ] to exit.

 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 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 determine 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 that -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 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 1800-468-1502. In Canada, write Retail Products ON15-02H,  Honeywell Limited/Honeywell Limitée, 35 Dynamic Drive, Toronto, Ontario M1V4Z9.


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

Reference Link

Honeywell RTH2520 Programmable Thermostat Installation Guide

Honeywell RTH2520 Programmable Thermostat Installation Guide

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Honeywell RTH2520 Programmable Thermostat Installation Guide


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