Thermostat "Filter" reminder: what it means and how to clear it
A filter reminder is a timer, not a sensor. The thermostat counts calendar days or system run time since the reminder was last reset, and when the count runs out it asks you to change the air filter. It keeps showing until you clear or reset it on the thermostat or in its app.
What does a filter reminder on a thermostat mean?
It means a countdown has finished. When the reminder is set up, the thermostat starts counting, either calendar days or the hours your system actually runs. When it reaches the interval you or your installer chose, it shows a message asking you to change the air filter in your heating and cooling system.
Nothing has gone wrong when it appears. Google puts it plainly: Nest thermostats use how often your system runs to estimate when a reminder is due. The thermostat has no way to look at the filter. That also means the reminder will not go away by itself after you change the filter. You have to tell the thermostat, so it can start counting again.
Google also explains why the reminder exists. A clogged filter makes the system work harder, and in extreme cases heat builds up and a safety shut-off makes the heating turn on and off by itself. Changing the filter is equipment maintenance, so this page covers only the thermostat side: the message, the interval and how to clear it.
What does the reminder look like on each brand?
| Thermostat | What you see | How to clear it |
|---|---|---|
| Honeywell Home T4 Pro, T6 Pro | Alert icon on the home screen; "REPL" (replace air filter) in the "ALRT" menu. T6 Pro code 181 or 182 | Menu, scroll to "ALRT", Select, Select, arrow to "CLER", Select |
| Honeywell Home T9, T10 | Red dot above the Menu icon and an alert message | Menu, Preferences, choose the reminder, "Reset Timer" |
| Honeywell VisionPRO TH8000 | An alert to change the furnace filter | Press RESET |
| Nest Thermostat E, Nest Learning Thermostat (3rd gen or earlier) | Reminder on the thermostat | Quick View, Settings, Reminders, "Reset" |
| Nest Thermostat, Nest Learning Thermostat (4th gen) | Only in the Google Home app, not on the thermostat | In the app: update "Last changed" under Air filter reminder |
| ecobee | Not stated | Not stated |
| Sensi | Email or app notification, not on the thermostat | Tap "Mark Complete" on the reminder in the Sensi app |
| LUX PRO P621U | Filter bar graph empty and "FILTER" flashing | Slide switch to "AIR FILTER", press UP and DOWN together |
On the T4 Pro and T6 Pro you also have the option to snooze: press Select when "SNZE" appears and the reminder comes back in 7 days. Resideo recommends changing the filter before clearing the reminder.
How is the reminder interval set?
Each brand counts differently, and on Honeywell's T-series pro models the interval is an installer setting.
| Thermostat | Counts | Choices in the manual | Factory setting |
|---|---|---|---|
| Honeywell Home T4 Pro, T6 Pro (setting 711, and 712 for a second filter) | Run time days or calendar time | 10 to 150 run time days; 30 to 75 calendar days; 3 to 15 calendar months | Off |
| Honeywell Home T9 (setting 7110) | Run time days or calendar time | 10 to 150 run time days; 30 to 75 calendar days; 3 to 15 months | Off |
| Honeywell VisionPRO TH8000 (function 0500) | Run time days | 10, 30, 60, 90, 120 or 365 run time days | Not stated |
| Google Nest | System run time | Adjustable under "Advanced configuration" in the app | Off |
| ecobee | Not stated | You choose how often under Furnace Filter | Not stated |
| Sensi | Calendar months or fan run time | Calendar duration in months | 3 months (calendar) |
| LUX PRO P621U | Days | Off, 30, 60, 90, 120, 180 or 365 days | Not stated |
On the T4 Pro and T6 Pro, the reminder settings sit in the installer setup menu (ISU), the same menu that holds the system type setting. The factory setting for the number of air filters is 0 and both reminders are "Off", so if you see "REPL", someone set it up. The VisionPRO TH8000 manual describes 10 run time days as "about 1 month" and 365 as "about 3 years", which shows how much slower run time builds up than calendar time.
Run-time counting is why the reminder can arrive at odd intervals. Sensi notes that a runtime reminder is based on fan run time and that the circulating fan counts too, so a circulate fan setting or a fan left "On" (see fan "On" vs "Auto") brings the reminder sooner.
How do you clear or reset it on the thermostat?
Once the filter has been dealt with, reset the count on the thermostat:
- Honeywell T4 Pro and T6 Pro: press Menu, then the arrow until "ALRT" shows. Press Select to see the alert, Select again, use the arrow to reach "CLER", and press Select.
- Honeywell T9 and T10: touch Menu, scroll to Preferences, select the reminder and touch "Reset Timer". Honeywell says you can instead extend the timer to remind you later.
- Honeywell VisionPRO TH8000: press RESET to cancel the alert.
- Nest Thermostat E and Nest Learning Thermostat (3rd gen or earlier): press the ring for Quick View, select Settings, then Reminders, and choose "Reset". You then enter the month you last changed the filter.
- Nest Thermostat and Nest Learning Thermostat (4th gen): use the Google Home app, under Settings, Notifications, Air filter reminder, and update "Last changed".
- ecobee: ecobee places filter reminders under Reminders & Alerts, then Reminder Preferences, then Furnace Filter, on the thermostat or in the app. The ecobee page we checked does not describe how to clear a reminder.
- Sensi: in the app, tap "Mark Complete" on the reminder.
- LUX PRO P621U: move the Set Slide switch to "AIR FILTER", press UP and DOWN together, then return the switch to RUN.
Has the filter been changed since the reminder appeared?
- Yes
Clear or reset the reminder on the thermostat using the steps for your model, so the count starts again.
- No
Do you want the reminder back in a few days instead?
- Yes
On a Honeywell T4 Pro or T6 Pro, snooze it for 7 days from the "ALRT" menu. On a T9 or T10, extend the timer.
- No
Leave the reminder showing until the filter has been handled. It does not affect how the system runs.
- Yes
Some Honeywell reminders arrive as numbered codes; our Honeywell error codes page lists them. On a Carrier Infinity control, the filter reminder sits alongside a separate service reminder; see Carrier thermostat service reminder.
Frequently asked questions
- Does my thermostat know the filter is dirty?
- Usually not. Honeywell, Google Nest, Sensi and LUX all describe their reminders as timers based on calendar days or run time. The thermostat cannot see the filter, so the reminder appears on schedule whether the filter is clean or not.
- Will clearing the reminder change how my system runs?
- No. LUX says its filter monitor is for information only and does not affect the heating or cooling equipment. Clearing or snoozing a reminder only restarts or pauses the countdown.
- Why did my Nest thermostat remind me sooner this winter?
- Google says Nest thermostats estimate the reminder from how long your system runs. A cold winter with long heating cycles uses up the count faster, and a mild season with little cooling can mean months without a reminder.
- Can I turn the filter reminder off?
- On the Honeywell and Nest models covered here, yes. On Honeywell T4 Pro and T6 Pro thermostats the installer setting 711 can be set to "Off", on the VisionPRO TH8000 function 0500 has an "Off" option, and on a Nest Thermostat E you choose "Don't Remind Me".