CT3600, CT3611, CT3500, CT3595, CT8602 Thermostat Filter reset addendum
I purchased and installed a Honeywell CT3500 programmable thermostat last year. It works very well and I am satisfied with it, however, after a few months an annoying “Filter” message began to blink at me. Since I have a baseboard hot water system (hydronic), I do not have an air filter, so I don’t need a reminder to change it. The owner’s manual does not say how to reset or defeat this function. I dug through the box and found an addendum to the owners manual that gives all the information needed.
Reset the filter timer by pressing the “i” key until the expired timer is displayed, then press the “Time up” key to reset it. After you are done, press the Run Program key.
To defeat the filter timers, see picture of addendum below.
Click on image to get a larger, readable .jpg.