The answer to 'when to service furnace' is that you should have your furnace serviced at least once a year, ideally before the start of the heating season. Regular maintenance is crucial to ensure your furnace is running efficiently and safely.
During an annual furnace tune-up, a professional HVAC technician will inspect the system, clean the components, and make any necessary adjustments or repairs. This helps extend the life of your furnace, improve its performance, and prevent costly breakdowns down the line.