Where to find the model number on a furnace

A furnace carries a rating plate: a label, often with a lot of small print, that lists the model and serial number along with the furnace's ratings. On many furnaces it's on the outside of a side panel. On others, including Carrier and Bryant, it's on the inside of the front door panel, which you remove by turning its knobs or lifting it up and out.

Where the label usually is

Most furnaces: look on the side panels first; if it isn't there, the label is just inside the front panel.

By brand

• TraneThe label is on the right or left side panel.
• Carrier, BryantThe rating plate is on the inside of the front door panel: turn the panel's knobs counterclockwise and pull it toward you.
• LennoxTake off the top front service panel; the label is on the left side of the cabinet inside, or on top of the blower deck.
• Rheem, RuudTake off the top front cover; the model and serial tag is inside it.

Each brand's spot is from that maker's own "where is my model number" page or manual, linked under Sources. Models vary, so if it isn't there, check the other spots above.

How to find and record the numbers

1. 1. Make it safeTurn the furnace's own power switch off (it looks like a light switch on or near the furnace) before you take a panel off, and put the panel back before you turn it on again. Never open the house's electrical panel to look.
2. 2. Look in the usual spot firstLook on the side panels first; if it isn't there, the label is just inside the front panel.
3. 3. Find the two numbersLook for the words Model (or M/N, Mod.) and Serial (or S/N, Ser.). The model is the product; the serial is your one unit.
4. 4. Take a sharp photoUse the flashlight at an angle so the label doesn't glare, and get the whole label in the frame. A photo beats copying by hand: 0 and O, 1 and I, 5 and S are easy to mix up.
5. 5. Keep it where you'll find itSave the photo with the appliance's name, or write both numbers on the receipt or in your home records.

Model number or serial number?

The model number names the product: every unit of that model shares it, and it's what you need for the manual, replacement parts and recall searches. The serial number is your one unit. Makers use it for warranty claims, and many build the date it was made into it, which is how you can tell an appliance's age without the receipt. Each maker uses its own code for the date, so look up your brand's pattern or ask the maker before you trust a guess.

What you'll use it for

The rating plate tells a pro most of what they need before they arrive: the fuel (natural gas or propane), the input rating, and the electrical details. The model number also finds the manual, which says what filter size and type the furnace takes and how often to change it, and the parts that fit, like the igniter or flame sensor. And it's how you match a recall notice or file a warranty claim, which usually needs the serial number too.

If the label isn't there

Check the lower panel (the blower door) as well as the upper one, and the back of whichever panel you take off. If the furnace sits in a tight closet or attic, take the photo with your phone held at arm's length. The installer's invoice, a sticker from the last service visit, or the home inspection report may list the model.

Questions people ask