Man inspecting furnace with a tablet.

How to Tell When Your Furnace was Made

A furnace lasts between 15 and 20 years, so getting a handle on the system’s history can help you budget for a replacement.

Unfortunately, the date of manufacture isn’t always clearly stamped on the unit. Determining your furnace’s age could take some HVAC archeology.

Step 1: Find the Label

Look for the label inside the front door of the furnace. The label should list the unit’s serial number. Not there? Keep reading.

Step 2: Check the Fan and Fan Blades

First, shut off the power to the unit either at the power switch or the switch at the breaker box. Next, find the serial number stamped on the fan or fan blades. Other places to check include relays and gas valves.

Step 3: Crack the Code

Now that you’ve (hopefully) found the serial number, you should be able to decode the system’s age. Often, the date of manufacture is baked into the serial number. Sometimes the first two digits of the serial number indicate the week of the year the system was made, while the third and fourth numbers point to the year. For example, if the first four digits are 1199, it can be reasonably assumed that the system was made in the eleventh week of 1999.

Now, if the system was made in the year 2000 or later, pay attention to the last four digits. A serial number ending in 0704 would suggest the furnace rolled off of the assembly line in July 2004.

Step 4: Keep Digging

If you still haven’t uncovered the serial number, consult the user manual. The original furnace manual should contain the system’s date. If that’s not an option, contact the manufacturer. A customer service representative may ask for a picture of your furnace to help determine its age. They may not be able to provide you a precise date, but they’ll at least know the decade it was manufactured.

Bottom line: Still stumped? Call the pros at Quality Degree, Inc. at (610) 600-1108 or fill out an online contact form. We can diagnose your heating system to help you determine how much longer it will last.