Written by Lori Lapierre; Updated December 29, 2018

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Purchasing an older home with an existing furnace can be a worry; a furnace often needs replacing after 15 to 20 years, so knowing its age is helpful in determining if a new furnace should be in the budget. Newer units may have a manufacturer's date listed somewhere on the furnace; older furnaces require a bit more digging by looking at the serial number, which tells the manufacturer various pieces of information, including the age. Finding the serial number, however, may also require a bit of sleuth work.

1. Pull off the removable door on the outside of your furnace; this is usually along the bottom of the front of the unit. Look at the interior of the metal door for a label or tag listing the furnace's serial number. This may also show an actual manufacturer's date, depending on the company that made the furnace.

2. Turn off the power to the furnace -- by either turning off the power switch or the master fuse to the unit -- and look at the fan and fan blades. Older furnaces sometimes had the serial number stamped onto the fan itself, giving the necessary information even when a manufacturing label is absent.

3. Look at the first four digits of the serial number once you find it. The first two digits can be the week of the year that the unit was manufactured, with the third and fourth number indicating the year. A serial number starting with 0193, for example, may have been made the first week of 1993.

4. Look for a sticker or tag that gives a date when the furnace was last serviced. This is usually common on gas furnaces and may list the date that the furnace was installed. This can often give a close approximation of the unit's age.

5. Call the manufacturer to get the age of the furnace. Even without a serial number, a manufacturer's rep may be able to look at a picture of the unit to give an idea of the period in which it was manufactured. If the company is out of business, having a home inspector or heating contractor look over the unit may be worth any fee charged to do so.

Tip

A furnace with ductwork fanning out that resembles an octopus is a 'gravity' furnace, dating pre-1950.

About the Author

Lori Lapierre holds a Bachelor of Arts and Science in public relations/communications. For 17 years, she worked for a Fortune 500 company before purchasing a business and starting a family. She is a regular freelancer for 'Living Light News,' an award-winning national publication. Her past writing experience includes school news reporting, church drama, in-house business articles and a self-published mystery, 'Duty Free Murder.'

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Age of Mueller Climatrol Furnace

Howdy, folks.

I've been searching online, trying to find the age of my furnace. I live in a condo building that was built in 1960 or so. It's a Mueller Climatrol (it reads 'Division of Worthington Corp.').

I took a look at a small ID plate from the manufacturer, but couldn't get a better look at the unit itself.

Lennox Serial Number Lookup

The plate says it's natural gas, serial number of 4IU, model number of 30-50, input = 50,000, output = 35,000. Another number below reads '10-0102-1.'

I couldn't find anything relating to this particular model online, and don't have access to a Preston's, so any insight from the Reddit community would be greatly appreciated.

I want to make sure my family is safe, so if this thing is dangerous, or just old, we want to get it out of here.

I'll try to get a photo posted.

Lennox Furnace Serial Number Age

Many thanks in advance.

Lennox Model Numbers