Modern furnace technology has allowed for heating systems with high efficiency that surpass anything built before. Where furnaces once averaged efficiency ratings of around 80% AFUE (meaning 80% of the fuel turns to heating energy and 20% escapes as exhaust), special high-efficiency condensing furnaces can score around 97% AFUE. This is because these high-efficiency furnaces are condensing furnaces. Condensing furnaces contain a second heat exchanger where the exhaust from the first heat exchanger is condensed to release even more heat.
Although a condensing furnace isn’t the ideal heating system for all homes and budgets, in the right home they’re a fantastic way to enjoy savings. But they can have some specific repair issues to watch for, specifically when it comes to combustion. We’ll look at a few of these combustion troubles below.