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Carrier family

How old is my Day & Night furnace?

Enter the serial number from the label. The date comes from Day & Night's documented serial rules, not a guess.

Look for “Serial No.” or “S/N” on the label. Spaces and dashes are fine.

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How to read a Day & Night furnace serial number

  • Week + year, plant letter, sequence (1988 onward)

    Example: 4006A17330 (Carrier) was made in October 2006. In Carrier, Bryant and Payne serials the first two digits are the week (40) and the next two are the year (2006). The letter after them is the factory.

Not decoded yet: Pre-1988 Carrier, Bryant and Payne formats (month letters, week + year letter, all-numeric) are not decoded because sources disagree.

Where to find the serial number

Turn the furnace off at its switch, then remove the upper access door (the burner or blower compartment). The rating plate is on the inside wall of the cabinet or on the back of the door.

The plate lists the model number and serial number; many newer plates also print a date of manufacture.

How long does a furnace last?

A typical furnace lasts about 15–20 years. That's a general estimate: maintenance, usage, climate and installation all matter, and age alone doesn't tell you a unit's condition.

Range from NAHB / Bank of America, Study of Life Expectancy of Home Components (2007, archived copy), Carrier: how long does a furnace last? and Lennox: how long does a furnace last?.

Day & Night furnace recalls

From the U.S. Consumer Product Safety Commission, checked 2026-09-29. A decoded result checks your model number against recalls live.

Questions

How can I tell how old my Day & Night furnace is?
Find the serial number on the rating plate and enter it above. Day & Night furnaces use the Carrier family serial format, which includes the manufacture date. For example, 4006A17330 was made in October 2006: In Carrier, Bryant and Payne serials the first two digits are the week (40) and the next two are the year (2006). The letter after them is the factory.
Where is the serial number on a Day & Night furnace?
Turn the furnace off at its switch, then remove the upper access door (the burner or blower compartment). The rating plate is on the inside wall of the cabinet or on the back of the door. The plate lists the model number and serial number; many newer plates also print a date of manufacture.
How long does a furnace usually last?
A typical service life is about 15–20 years. That's a general estimate: maintenance, usage, climate and installation all matter, and age alone doesn't tell you a unit's condition.
Do Carrier, Bryant and Payne furnaces use the same serial format?
Yes. Day & Night, Carrier, Bryant and Payne use the same serial-number conventions (Carrier family), so the same decoding rules apply.
How reliable is the result?
The Carrier family rules come from documented sources, but they're in Beta while we check more real-world examples, so results are capped at medium confidence. If a serial doesn't match a documented format, we say so instead of guessing.

Same serial format: Carrier furnace, Bryant furnace, Payne furnace

Other Day & Night equipment: air conditioner, heat pump

Sources

Rules last reviewed 2026-09-28. These rules are in Beta while we verify more real-world examples, so results are capped at medium confidence.

Manufacture dates are decoded from manufacturer serial-number conventions and available documentation. Serial formats can change. Verify critical equipment information with the manufacturer when necessary.