Honeywell RTH221B Programmable Thermostat Installation Guide
- June 7, 2024
- Honeywell
Table of Contents
Honeywell RTH221B Programmable Thermostat
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Operation
Controls
Display screen
When Cool On is flashing, this means the compressor protection is engaged (see section 1.7).
Setting the clock
- Press the Set button. The message Set Time will appear on the screen and the time display will flash.
- Press the up or down button to set the time.
- Press the Run button to save the changes & exit. (The changes are also saved if you do not press any button for 60 seconds.)
NOTE: The clock has lost its settings when the time display flashes. If the thermostat is following the programmed schedule, it will use the temperature settings programmed for the Wake period until you readjust the clock.
System switch
Use the System switch to place the system in one of the following modes.
- Cool: System is in Cooling mode.
- Off: System is off.
- Heat: System is in Heating mode.
CAUTION: EQUIPMENT DAMAGE HAZARD
Do not use Cooling mode when the outdoor temperature is below 50 °F (10 °C).
Fan switch
Use the Fan switch to select the fan operation.
- Auto: The fan runs only when heating or cooling is actually taking place (commonly used setting).
- On: The fan runs continuously.
Temperature setting
Press the up or down button once to display the setpoint temperature.
Press either button more than once to change the setpoint.
The ambient (measured) temperature is normally displayed. To view the setpoint
temperature, press either of the temperature adjustment buttons once. The
setpoint temperature will appear for five seconds.
Built-in compressor protection
Your thermostat has a feature that helps prevent damage to the compressor of
your air conditioning system. Because damage can occur if the compressor is
restarted too soon after shutdown, this feature forces the compressor to wait
five minutes before restarting.
During the wait time, the message Cool On flashes on the screen.
When the safe wait time has elapsed, the message stops flashing and the
compressor turns on.
Programmed schedule
Using the schedule
Press the Run button to follow the programmed schedule. You can have up to
four periods in one day. Each period can be programmed with a different
temperature setting.
| Wake | Morning temperature |
|---|---|
| Leave | Daytime temperature |
| Return | Evening temperature |
| Sleep | Night temperature |
To program a period, you need to set its start time and its two temperature settings (one when the thermostat is in cooling mode and another one when it is in heating mode). The same period and settings are repeated every day.
For maximum energy savings without sacrificing comfort, you can program the schedule such that the temperature is at an economical level when you sleep or are away during the day and at a comfortable level when you are awake and at home.
Factory settings
| Period | S t ar t time | Heat | Cool |
|---|---|---|---|
| W ake | 6:00 a.m. | 70 °F (21 °C) | 75 °F (24 °C) |
| Le ave | 8:00 a.m. | 62 °F (16.5 °C) | 83 °F (28.5 °C) |
| Retu rn | 6:00 p.m. | 70 °F (21 °C) | 75 °F (24 °C) |
| Sleep | 10:00 p.m. | 62 °F (16.5 °C) | 78 °F (25.5 °C) |
Modifying the schedule
-
Press the Set button twice until the message Set Schedule appears. The start time of the first period (Wake) will flash.
-
Press the up or down button to set the time.
-
Press the Set button. The temperature setting for that period will flash.
-
To program the temperature settings for the cooling mode, place the System switch in Cool. To program the temperature settings for the heating mode, place the switch in Heat.
-
Press the up or down button to set the temperature.
-
Press the Set button. The start time of the next period will flash.
NOTE: To skip a period, press the Hold button for four seconds while that period is displayed. When a period is skipped, dashes appear instead of the time and temperature display for the period. Only the Wake period cannot be skipped. -
Repeat steps 2 through 6 for each of the remaining periods.
-
Once all adjustments are made, press the Run button to save them and exit. (The changes are also saved if you do not press any button for 60 seconds.)
Temporary override of schedule
To temporarily ignore the programmed schedule, press up or down until the desired temperature is displayed. The word Temporary will appear on the screen and the period display will flash to indicate that the current period has been overridden. The new temperature will be used until the next period begins.
NOTE: Pressing up or down once will display the setpoint temperature. To change the setpoint temperature, press either button more than once. Press the Run button if you wish to cancel the temporary setting before the beginning of the next period.
Permanent override of schedule
To permanently ignore the programmed schedule, press up or down until the
desired temperature is displayed. Then, press the Hold button to maintain the
new temperature indefinitely. The word Hold will appear on the screen.
Press the Run button if you wish to cancel the override and resume the
programmed schedule. The word Hold will disappear and the thermostat will be
set to the temperature programmed for the current period.
Battery replacement
Set the System switch to Off before removing the batteries. Otherwise, the heating/cooling system could remain activated even when batteries are removed.
Install two fresh AAA batteries when Lo Batt (low batteries) flashes on the
screen. The icon appears for 60 days before the batteries are depleted.
Replace batteries once a year, or when you will be away for more than a month.
Most settings are stored in non-volatile (permanent) memory. Only the clock
must be set if the thermostat was without batteries.
In case of difficulty
Screen is blank: Ensure two fresh AAA alkaline batteries are correctly installed.
Temperature settings cannot be changed:
- The System switch is off.
- You are setting the temperatures outside their allowable ranges:
- Heat: 40 °F to 90 °F (4.5 °C to 32 °C).
- Cool: 50 °F to 99 °F (10 °C to 37 °C).
Cool On is flashing: The compressor protection delay has been activated. Cooling will not be activated until the delay ends (maximum of five minutes).
HI appears on the screen: The ambient (measured) temperature is above 122 °F (50 °C).
LO appears on the screen: The ambient (measured) temperature is below 32 °F (0 °C).
E1 appears on the screen: The temperature sensor circuit is opened. Replace the thermostat.
E2 appears on the screen: The temperature sensor circuit is shorted. Replace the thermostat.
Technical Data
Power Supply
• 2 AAA batteries
Maximum Load
• 1 A @ 24 VAC per output
Temperature Ranges
• Heat: 40 °F to 90 °F (4.5 °C to 32 °C)
• Cool: 50 °F to 99 °F (10 °C to 37 °C)
Operating Ambient Temperature
• 32 °F to 122 °F (0 °C to 50 °C)
Shipping Temperature
• -40 °F to 130 °F (-40 °C to 55 °C)
Operating Relative Humidity
• 5% to 90% (non-condensing)
Physical Dimensions (H x W x D)
• 4.7” x 2.9” x 1.1” (120 mm x 74 mm x 28 mm)
Warranty
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,
- return it, with a bill of sale or other dated proof of purchase, to the place from which you purchased it, or
- 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 regarding your thermostat, please go to http://yourhome.honeywell.com, or call Honeywell Customer Care toll-free at 1-800-468-1502.