Nordyne / Intertherm / Miller / Maytag / Frigidaire / Tappan / Westinghouse / Kelvinator / Gibson / Broan heating and cooling equipment carry the build date inside the serial number. We know 2 serial formats for this brand; the decoder tries each one and shows every reading that fits.
Skip the first three characters (a model code). The next two digits are the year and the two after that are the month.
GBB030708229 reads as July 2003.
Two sources agree Building Intelligence Center, Energy Trust of Oregon furnace chart, InspectAPedia, InterNACHI inspector forum
Find the single letter in the middle of the serial (often F, M, G, N or W). The two digits after it are the week and the next two are the year.
MN3D102F38914228 reads as week 38 of 1991.
One source Building Intelligence Center
A gas furnace usually lasts 15 to 20 years. Well-maintained units in mild climates reach 25; units that run hard with dirty filters fail sooner.
How long does a furnace last? · Should I replace my furnace? · HVAC.com, Lennox, InterNACHI (15-25)
A central AC condenser usually lasts 12 to 15 years. In hot climates where it runs most of the year, 10 is more typical; in the north, 20 is possible.
How long does a central air conditioner last? · Should I replace my air conditioner? · Bryant, Lennox, InterNACHI (7-15)
An air-source heat pump usually lasts 10 to 15 years. It runs in both seasons, so it logs more hours than a furnace or an AC alone.
How long does a heat pump last? · Should I replace my furnace? · Trane, Lennox, Bryant, InterNACHI
Should I replace my furnace? · Should I replace my air conditioner?
Goodman · Amana (heating and cooling) · Daikin · Carrier · Bryant · Payne · Day & Night · Heil / Tempstar / Comfortmaker / Arcoaire / KeepRite · Lennox · Armstrong Air / AirEase / Concord / Allied · Ducane · Aire-Flo · Trane · American Standard (heating and cooling) · York · Luxaire · Coleman / Evcon · Fraser-Johnston / Champion / Guardian · WeatherKing · Comfort-Aire / Heat Controller / Century
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The age you just looked up is the kind of fact that gets lost. A written record of serial numbers, install dates, repairs and who did the work saves the next owner, inspector or insurer from guessing.
A lifetime logbook for the house, organized by system, with room for serial numbers, install dates, repairs and contractors. It stays with the house for the next owner.
Galvanized, polybutylene, cast iron and the sewer line: what fails, what it costs, what insurance won't cover and how to decide.
A buyer's guide to older homes: wiring, pipes, lead, asbestos, insurance refusals and what the repairs actually cost.
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