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How old is my Miller furnace or AC?

Type the serial number from the Miller label to see when it was built. Miller units are built by Nordyne (owned by Rheem since 2024), so the serials follow that company's format.

Example

GBB030708229

GBBProduct code, not part of the date
03Year: 03 = 2003
07Month: 07 = July

Built July 2003

23 years, 3 months old

In replacement window. Inside the usual 15 to 25 year lifespan, so replacement could come any time. Worth budgeting for it.

What to do now

Get a replacement quote now, before a breakdown in the hottest or coldest week forces a rushed choice.
A common rule of thumb: if the repair cost times the age in years is over 5,000, replacing usually makes more sense.
Ask about rebates. Many utilities and states pay toward a high-efficiency replacement.
Some home insurers and home buyers’ inspectors ask the age of the HVAC system. Florida 4-point inspections record it.
Most HVAC parts warranties run 5 to 10 years and require registration within 60 to 90 days of install. Check with the installer.

How this was read

Skip the first three characters, GBB. They are a product code.
The next two digits, 03, are the year: 2003.
The two digits after that, 07, are the month: July.

Format: Nordyne three-character prefix, year and month. Sources: Energy Trust of Oregon: furnace age brand details (PDF), Building Intelligence Center: Nordyne, Building Intelligence Center: Maytag, Building Intelligence Center: Intertherm.

Reading a Miller serial number

Miller is a Nordyne brand for manufactured homes. After a three-character code come the year and the month.

About Miller

Miller electric furnaces for manufactured homes share the E7 series design with Intertherm and Broan.
Rheem has owned Miller’s maker, Nortek Global HVAC, since October 2024.

Sources: Nortek Global HVAC: Electric Furnace (ACHR News), Rheem to acquire Nortek Global HVAC (ACHR News)

Nordyne three-character prefix, year and month

Used about 1989 to today. Example: FGA030310579

The serial starts with three characters, then the year (2 digits), then the month (2 digits). FGA 03 03 means March 2003. Frigidaire, Gibson, Maytag, Westinghouse, Intertherm and Miller furnaces share this format.

Worked example: GBB030708229 was built July 2003, so it is 23 years, 3 months old as of October 2026.

Sources: Energy Trust of Oregon: furnace age brand details (PDF), Building Intelligence Center: Nordyne, Building Intelligence Center: Maytag, Building Intelligence Center: Intertherm

Miller recalls

Recalls from the U.S. Consumer Product Safety Commission that name Miller. Whether a unit is included depends on its model and build date; the checker above flags matches.

Year	Recall	Hazard
1996	Ducane-built oil furnaces sold under many brands	The heat exchanger can crack.

Standing at the unit? Use your phone

Point your phone’s camera at this code. The scanner opens and reads the label for you.

Same serial number format as Miller: Broan, Frigidaire, Gibson, Intertherm, Maytag, Tappan, Westinghouse.

Formats on this page were last checked against their sources in October 2026. Miller is a trademark of its owner. This page is independent and not affiliated with or endorsed by Miller. For warranty questions, contact Miller directly.

Where the serial is on a Miller

Miller furnaces in manufactured homes carry the rating plate inside the front door of the furnace.

Turn off the furnace switch before removing the front door. The outdoor unit’s plate is usually on the side panel near the electrical connections, sometimes on the back.