How to Determine the Age of a Furnace

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Whether you’re purchasing an older home or live in one already, it’s worth checking how old the furnace is. According to Carrier, a company founded in 1915 and specialized in HVAC systems, life expectancy of furnaces range between 15 to 20 years. Once the furnace is about 15 years old, it’s time to start looking for a replacement unit. Having that in mind, you’ll get a better overview of your budget for your current or upcoming house.

Determining how old a furnace is, can be a bit tricky unless you know what to look for. New units may have the manufacturing date printed on a label, while older models may require a bit of sleuth work.

How to easily determine the age of a furnace

First, we recommend that you look for a label which is usually stuck onto the furnace. This label is likely to present the information you need, such as the manufacturing date and a model number.

If you’re unable to locate any labels, look for a stamp or text printed on the furnace. This could be the name of the manufacturer, model name, or perhaps a serial number. Sometimes you’ll have to brush off a layer of dust to reveal this information, so make sure you bring a handheld vacuum or a brush. With this information at hand, the manufacturer might be able to assist you and give you an idea of how old the furnace is.

Below is a step by step guide that will walk you through the steps needed to determine how old your furnace is.

Step 1 – Access your furnace

You should be able to locate a door on the outside of your furnace, likely at the bottom of the front of the unit. There are many different ways to hide a furnace, so bring a flashlight if it sits in a poorly lit area of your house. A flashlight helps you locate labels, tags, or other crucial information.

Step 2 – Look for a label or a tag

This step is either very simple or complicated, depending on the make and model you have. Look at the unit for any label or tag that has information on it, or look at the interior of the metal door for any information.

If you’re unable to find any labels or tags on the exterior parts of your furnace, you may have to switch off the power and look at the fan or fan blades. Sometimes, especially with older furnaces, the information is stamped or printed onto the fan or fan blades.

If the label or tag doesn’t show a manufacturing date but instead has a serial number on it, you may be able to extract the information needed by deciphering the serial number itself.

According to this chart on Inspectapedia, the manufacturing date can often be found in the serial number. 

Step 2.1 – Look for a ‘last service’ sticker

Just like you’d see in most elevators, gas furnaces are regularly inspected and serviced by a professional. They often leave a sticker on your gas furnace with some information that could be helpful when determining the age of your furnace.

A ‘last service’ sticker could hold valuable information that could help determine how old your furnace is.

Step 3 – Write down the info or take a photo

Sometimes, older furnaces won’t have a manufacturing date printed directly onto any labels. Maybe there’s no information to find except a serial number, and it doesn’t necessarily provide you with any helpful information.

Write down any information you can find, and take a few photos of your furnace. If possible, take the photos during the day where natural light is available. Otherwise you could use a work light or a regular lamp to ensure that the furnace is properly lit up while taking the photos.

Show the information and photos to a professional, or post them online for advice. If you manage to find a local Facebook group, you may be able to find someone knowledgeable who can chip in with the information needed.

Step 4 – Ask the manufacturer

If you’re only able to determine the name of the manufacturer, you can take a few photos and send them over. The manufacturer could then look at the photos and get back to you with some information. Maybe they’re able to estimate the age of your furnace, or they can tell you where to look for the serial number in case you couldn’t find it.

More often than not, they don’t even have to physically inspect your furnace to assist you with the information needed. 

What if you can’t find any label or sticker telling you the age of your furnace?

If your furnace doesn’t have any visible stickers, labels, or tags, how are you going to determine its age? It may seem a bit confusing as to what’s the next step, but fortunately there’s a solution for this.

Below are a few different scenarios that we will guide you through.

If you know the manufacturer, but your furnace has no labels, stickers, or tags

In this case, we recommend calling the manufacturer. They could possibly give you an estimate of the manufacturing year by looking at pictures or asking a few questions, but in some cases a physical inspection is needed.

If you don’t know the manufacturer, and your furnace has no visible labels, stickers, or tags

In this case you could start your search by joining a few niche-relevant Facebook groups, such as “HVAC Questions & Answers” or similar. In these groups you can post pictures of your furnace and ask if anyone knows the make and model of your unit. These groups often 

Explain how a manufacturer could still help you with an age estimate based on a visual inspection.

If the manufacturer went out of business

If the manufacturer went out of business and you can’t find any manufacturing date on your furnace, there’s still an opportunity to determine the age of the unit. Numerous experts across the country could help, so look for local HVAC professionals and give them a call.

You could also reach out to them online, and perhaps send them a few pictures. They can very likely tell you exactly what model you have, simply by seeing a few pictures.

How do you know if your furnace is too old?

Furnaces have a normal lifespan of somewhere between 15 to 20 years, with some models getting up to 30 years or older before showing signs of aging.

The general advice is to buy a new furnace at the 15 year-mark, before any warning signs start showing.

Below are a few warning signs to look out for, if you know your furnace is soon due for replacement.

1. Energy bills and equipment repairs are on the rise

A telltale sign that your furnace is getting old, is increasing energy bills as well as the need of frequent repairs. Basically, furnaces are like cars — parts start breaking, and they need repairs to stay afloat.

If your energy bill is rising and you find yourself calling technicians more often than usual, your furnace may be due for a replacement.

2. Furnace is already more than 15 years old

This is probably one of the most obvious signs that your furnace is getting too old. Once it hits the 15 year-mark, it’s time to consider a new model. Rest assured that your furnace may work well for years to come, but the chances of something breaking and/or malfunctioning increase every year.

3. You notice different temperatures in different rooms

Maybe you’ve noticed that one bedroom is colder than the other, and your thermometers confirm this. Old furnaces are not always capable of distributing the heat properly, as they can become more inefficient until the point where they lose the ability to distribute the heat to every room of your house.

4. Soot around the registers

If you notice soot around the registers, it could be a sign of excessive amounts of carbon monoxide being produced in your furnace. This could be due to a malfunctioning furnace, but it could also be caused by dirty filters. If your furnace isn’t well taken care of, this issue could occur from time to time.

Because carbon monoxide is extremely dangerous, this issue calls for an emergency inspection by an HVAC technician.

5. Furnace is becoming increasingly noisy

If you start noticing any rattling, humming, poppen or squealing sounds coming from your furnace and it gets louder over time, it’s a sign that something is about to give in.

Call a technician for an inspection as soon as possible, as your furnace could break down at any point if the problem isn’t addressed.