“Change Filter” or “time to clean filter” is displayed on my thermostat, and I just changed the air filter. Maybe my thermostat says, “Replace Air Filter,” it doesn’t even know I have a filter, let alone when it needs to be changed. It reminds me of the saying, “The left-hand doesn’t know what the right hand is doing”?
Filter alerts on digital thermostat displays are basically just a timer. So if you want to know how to change a thermostat filter, you must know that thermostats don’t have filter, but furnaces do. Also know that it’s just a simple reminder like an alarm clock telling you that furnace filters need changing now and again.
Some thermostats have settings that you can turn on or off and even change the period of time between filter changes. The best way to know how to change the settings is to check your thermostats owners manual or installation instructions.
Owner manuals are generally available online by looking up the model number of your thermostat with the words “owners manual”. The model numbers for thermostats are usually found by removing the thermostat from the wall and looking on the back. Not always, but most of the time.
One of the questions I get is how to change a thermostat filter. Well, sense thermostats don’t have filters, those people asking that question must be just formulating their question awkwardly. They surely mean to ask how do you reset a thermostat after changing the filter.
Their must be dozens of thermostat brands all with a different way of doing a reset of the filter timer. Really the best way is to refer to the owners manual.
So How Often Should I Change My Furnaces Air Filter?
Most manufacturers recommend changing your furnace filter every three months. My experience is that there is no set time because every home and home owner is different. Some have pets and some don’t. Others have lots of kids running in and out of doors.
The only true way to know when a furnace filter needs to be changed is to measure pressure drop across a component, such as a filter, with a monometer. Amazon has a simple manometer here that is easily installed and read. Not an electronic gadget, but a proven long time method of measurement.
Manufacturers of HVAC equipment publish the preferred static pressure they require. It is somewhat involved in more than what this article is about. I mainly want you to explore the static pressure drop across your filter.
Once you understand the principles of measuring static pressure you can then take a static pressure reading across your filter and record a reading for a clean new filter. Then monitor the filter as it becomes loaded.
The normal static pressure drop across a MERV 8 filter should be in the range of .15 give or take a little. Here is an article that explains it more thoroughly.
