Set FAN Auto On Electronic Thermostat Room SYSTEM Cool Off Heat OWNER’S GUIDE 1 69-1491–1 69-1491-1
Congratulations on the purchase of your new thermostat! Over 100 years of Honeywell engineering expertise went into the making of this thermostat in an effort to provide you with a more comfortable and convenient living environment. • Simple and easy to use. The ▲ and ▼ keys make it easy for you to change your temperature setting. • Large digital display. You can easily read the current room temperature at a glance. • No need for batteries.
Settings Setting FAN and SYSTEM Switches Fan and system settings are controlled by using FAN and SYSTEM switches located on the bottom of the thermostat case. First set the FAN switch: Auto: Normal setting for most homes. In cooling, the fan goes off and on with the cooling equipment. In heating, the fan may start a few minutes after the heating equipment comes on. On: The fan runs continuously. Use for improved air circulation and air quality.
Then set the SYSTEM switch: Cool: Normal setting for months when your home needs cooling (air conditioning). Digital display shows a snowflake when cooling is on. Off: Both heating and cooling are off. Heat: Normal setting for months when your home needs heating. Digital display shows a flame when heating is on. SYSTEM Cool Off Heat SYSTEM SWITCH M14228 IMPORTANT Do not operate the T8400 and T8401 in cooling mode when the outdoor temperature is below 50°F (10°C), or damage to compressor could result.
Displaying Temperature Setting NOTE: Your temperature setting can be set anywhere from 40° to 99°F (5° to 37°C). The temperature setting and the room temperature are shown separately on the digital display. The ▼ indicator points to Set when the temperature setting is displayed and to Room when the room temperature is displayed. 1. To display the temperature setting on the digital display, press either the ▲ or ▼ key once.
Changing Temperature Setting 1. To lower the temperature setting, press the ▼ key. When in the heating mode, lowering the temperature at night or during the day can lower your energy costs. Set Room M18442 2. To raise the temperature setting, press the ▲ key. When in the cooling mode, raising the temperature before you leave for work or school also lowers your energy costs.
Troubleshooting Guide CAUTION Operating at too low of an outdoor temperature may cause compressor damage. Damage to compressor possible. Do not operate cooling if outdoor temperature is below 50°F (10°C). Refer to manufacturer’s recommendations. Heating or cooling does not come on. • Check power to the heating or cooling equipment. For compressor protection on initial startup and during power interruptions, the T8400 and T8401 Electronic Thermostats go into a five-minute delay.
• Check the system fuse or circuit breaker and replace or reset if necessary. • Check for air movement at the register. Temperature setting is too warm or cool • Adjust the temperature by pressing either the ▲ or ▼ key. If you have questions concerning this thermostat, call Honeywell Customer Assistance at 1-800-468-1502.
