AprilAire 8400 Series Thermostats — Owner's Manual

Owner's manual for the AprilAire 8400 Series thermostats (Models 8444, 8446, 8448, 8463, 8465, 8466), covering non-programmable and programmable operation, program schedule setup, temporary/permanent overrides, and battery/reset instructions.

About Your New Thermostat

Thermostat Features (All Models)

• Large, clear, backlit display — easy to read even in the dark
• Displays room temperature, temperature setting, and optional outdoor temperature
• Front battery door access for fast, easy replacement
• Built-in compressor protection
• Circulation fan mode for air cleaning
• Air filter, humidifier, dehumidifier, and HVAC service reminders
• Auto backlight (activated with first button press)

Additional Features — Programmable Models Only (8463, 8465, 8466)

• Separately programmable weekday/weekend schedules
• Easy-to-use temperature control can override the program schedule at any time
• Progressive recovery

How to Identify Your Thermostat's Model Number

To locate the model number, remove the battery cover.

Quick Reference to Controls & Display

Non-Programmable Models (8444, 8446, 8448) display: current indoor temperature, outdoor temperature (optional), system mode setting, temperature setting, equipment status, fan setting, up/down buttons, and (heat pump models only) Emergency Heat (red) and System Fault (yellow) indicators showing through the housing. Also includes a quick reference card, message center, low battery warning, and battery door.

Programmable Models (8463, 8465, 8466) add: current time, current schedule period, program button, and hold button, in addition to all non-programmable display elements.

Note: The backlight activates with the first button press and automatically turns off.

Operation (All Models)

Select System Mode (AUTO/OFF/HEAT/COOL/EM-HEAT)

• AUTO: Thermostat automatically selects heating or cooling depending on indoor temperature.
• OFF: Heating and cooling systems are off.
• HEAT: Thermostat controls only the heating system.
• COOL: Thermostat controls only the cooling system.
• EM-HEAT: Thermostat controls emergency/auxiliary heat; the heat pump will not operate. (Only available for heat pumps with auxiliary heat on models 8446, 8465, 8448HP, and 8466HP.)

Change Temperature Setting

Applies to programmable models (8463, 8465, 8466) when in HOLD mode, and to non-programmable models (8444, 8446, 8448). Use the up/down buttons to adjust the current setting. In AUTO mode, use the mode button to switch between the HEAT and COOL setting.

Select Fan Setting (ON/AUTO/CIRC)

• ON: Fan runs continuously — use for maximum air circulation/cleaning.
• AUTO: Fan runs only when the heating or cooling system is on.
• CIRC: Same as AUTO, but ensures the fan runs at least 20 minutes per hour — a balance of energy savings and air circulation/cleaning.

Reset Service Reminder Messages

Press and hold the two designated buttons simultaneously for three seconds to reset a service reminder message.

Battery Installation and Reset Button

The thermostat can be AC-powered, battery-powered, or both. When wired for AC power, batteries are optional and only provide backup power to the clock. A memory backup saves the thermostat's settings in case of a power interruption. The reset button, located under the battery cover, resets the thermostat to factory defaults.

Operation & Programming (Programmable Models Only: 8463, 8465, 8466)

Set Time and Day

1. Press the time button to enter time setting mode — the hour and AM/PM will flash.
2. Use up/down to adjust the hour.
3. Press to advance to minutes; use up/down to adjust.
4. Press to advance to the day; use up/down to adjust.
5. Press to end — "DONE" displays. The thermostat saves changes and returns to Normal mode if no key is pressed within 20 seconds.

Understanding Program Schedules

The daily schedule is split into four sections with default times and temperatures:

• WAKE (6:00am-8:00am): Temperature you'd prefer to wake up to, until you leave for the day.
• LEAVE (8:00am-5:00pm): Temperature when you're away during the day.
• RETURN (5:00pm-10:00pm): Temperature you'd prefer upon returning, until bedtime.
• SLEEP (10:00pm-6:00am): Temperature you'd prefer during the night.

All start times and temperatures can be customized to fit your schedule.

Progressive Recovery

If enabled by the installer, Progressive Recovery activates the heating/cooling equipment prior to a scheduled event so the desired temperature is reached by the start of that event. While a Progressive Recovery call is active, the current event schedule indicator flashes. Example: with WAKE set to 6:00am at 70°, the heat will start running before 6:00am so the room reaches 70° right at wake time.

Changing Program Schedules

1. Press the program button twice to enter program setting mode (if the backlight wasn't already active, the first press only activates it — two more presses are needed). The WAKE event start time will flash.
2. Use up/down to adjust the start time.
3. Press to advance — the HEAT setting flashes; use up/down to adjust.
4. Press to advance — the COOL setting flashes; use up/down to adjust.
5. Press to advance to the next event, repeating steps 2-5 for LEAVE, RETURN, and SLEEP.
6. Press to switch to the weekend program and repeat steps 2-5 for the weekend schedule.
7. Press to end — "DONE" displays. Changes save automatically if no key is pressed within 20 seconds.

Program Schedule Overrides (Temporary, Permanent)

• Temporary Override: Press up/down to immediately adjust the temperature. This temporarily overrides the setting for the current programmed time period only; the new setting holds until the next scheduled time period. To cancel, adjust the temperature back to the programmed value, or press the designated button twice (accounting for the backlight activation press if needed).
• Permanent Override: Press the designated button to permanently hold the current temperature, overriding all time periods of the programmed schedule. The thermostat can still be manually adjusted and will stay at whatever setting you choose until the override is cancelled. To cancel, press the same button again.

Limited Warranty

The AprilAire Thermostat is warranted for five (5) years from the date of installation against defects in materials or workmanship. Any modification voids the warranty. AprilAire's exclusive obligation under this warranty is to supply a free replacement for any thermostat found defective within the 5-year period, if returned no later than 30 days after that period, to the original supplier or to AprilAire, Madison, Wisconsin 53701, along with the installation date.

This warranty does not cover labor costs and does not apply to defects in workmanship or materials furnished by the installer (as opposed to defects in the thermostat itself). Implied warranties of merchantability or fitness for a particular purpose are limited to the same five-year period. Liability for incidental or consequential damages (other than personal injury) is expressly excluded. This limited warranty is void if the defect results from failure to have the thermostat installed by a qualified heating and air conditioning contractor — in that case, all disclaimers of implied warranties take effect upon installation.

Manufacturer

AprilAire, Madison, Wisconsin 53701.