>Is the 3 months interval a regional thing, or based on the heat exchanger?
both. That is it varies between different units but also varies with local conditions, if your local conditions are "heavy-duty" (very high humidity, smog, area with lots of dust or lots of pollens etc.) you should consider replacing more frequently than rated intervals.
both. That is it varies between different units but also varies with local conditions, if your local conditions are "heavy-duty" (very high humidity, smog, area with lots of dust or lots of pollens etc.) you should consider replacing more frequently than rated intervals.