Before furnaces were invented, many hours of each day were devoted to chopping and stacking wood, ensuring there was adequate fuel for a fire to keep a family warm. Today, a warm house and the furnace that provides that warmth are often taken for granted. Although annual furnace maintenance should be a priority, many furnaces are left to age in the dusty confines of basements, attics and garages until there's a problem. According to Bob Vila, most furnaces are meant to last 15 to 20 years, but determining the exact age of a furnace can be challenging.
How to Determine Furnace Age
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Step 1: Check Out the Furnace
Don't expect a date of manufacture to be plainly listed on an older furnace. Instead, look on the surface of the furnace for a paper or metal tag that contains a serial number and/or the name of the furnace manufacturer. The age of the furnace isn't always easy to detect from the label, so you might need to check out other furnace parts for information. Other places to look for serial numbers are relays or gas valves (and while you're looking all around, this might be a good time to note if your furnace needs a tune-up). Typically, furnaces over 30 years old don't have serial numbers to help in determining the age of the furnace.
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Step 2: Note the Serial Number
Write down the serial number found on the data tag. The date of manufacture is sometimes encoded within the serial number, but you need a furnace chart with manufacturer names, serial numbers and model numbers to consult to figure out the "hidden" furnace date.
Step 3: Look Up the Serial Number
Determine the age from the serial number if possible. Some serial numbers can be interpreted by weeks and years. So a number reading 1193CA4567 would be dated as the 11th week of 1993. Serial numbers from furnaces made after the year 2000 are often easier to decipher. For example, the serial number might have a six-digit code at the end that yields the furnace date.
Step 4: Use a Furnace Age Chart
If you're able to find a serial number, you can consult a furnace age chart using the manufacturer name, model of the furnace and serial number. There are many charts and books that list the information contained on your data tag to decode the furnace age.
Step 5: Look at the Furnace Manual
If you were lucky enough to receive the furnace manual from your home's previous owner, that's one place to check for a manufacture date. If your furnace lacks a data tag with an identifying serial number and you have the original furnace manual, there might be a date in the manual that dates the furnace.
Step 6: Contact the Furnace Manufacturer
Contact the furnace manufacturer if the company is still producing furnaces. Often companies are absorbed by other companies and you must do some detective work to discover the present name of the company that made your furnace. You will have to have a model number and/or a serial number for the company to help you in any way.