Hearing that you have a red-tagged furnace is never good news, since it almost always means either an expensive repair or a furnace replacement. This kind of furnace problem typically results from a cracked heat exchanger, the part that sits beside or above the burner. The heat exchanger is a metal piece that transfers heat from the burners to the air before it gets distributed through your home.
The primary cause of premature cracking is the lack of maintenance, which includes letting the air filter for the blower get too dirty. A clogged filter cuts down on the airflow going over the heat exchanger, keeping it hot longer. Heat contributes to metal fatigue. If you don't have your furnace cleaned regularly, dust also builds inside it, insulating the parts, which retain the heat.
Cracking presents a serious problem because it may emit carbon monoxide (CO) into your home's air. This is why if an HVAC professional discovers a serious crack in your heat exchanger, he will make your furnace inoperable – often denoted with the notorious red tag – until the issue is resolved. Getting a second opinion from another experienced HVAC contractor is a good strategy after hearing you have a red-tagged furnace.
A number of methods and tools are available to HVAC professionals to diagnose a cracked heat exchanger. Visual inspection may reveal cracks, some of which may be superficial, while others could be serious. If rust is inside the blower cabinet, the technician will probably look deeper into the system. Rust occurs when the air conditioner doesn't drain properly in the summer (if your furnace serves as the A/C's blower).
Sometimes HVAC experts use chemicals to trace combustion gases leaking from the heat exchanger, or use hand-held CO detectors. Sometimes the color of the flame may indicate a serious problem with the furnace.
If your home has an older combustion furnace, installing at least one CO detector will alert you should the furnace start to malfunction. If the alarm goes off during or shortly after the furnace runs, the heat exchanger may be the problem. Having your furnace professionally maintained before or during the heating season will also help put your mind at ease.
If you would like more information about a red-tagged furnace, contact Joe Behr Plumbing and Heating. We've provided superior HVAC services for the Mid-Ohio area since 1965.
Our goal is to help educate our customers in the Mid-Ohio area about energy and home comfort issues (specific to HVAC systems). For more information about red-tagged furnaces and other HVAC topics, visit our website.