Bryant is Carrier's sister brand and uses the identical serial format: week and year in the first four digits, then a plant letter.
The first two digits are the week and the next two are the year. The letter in the fifth spot is a plant code.
3709E07806 reads as week 37 of 2009.
Two sources agree Building Intelligence Center, PickHVAC, Energy Trust of Oregon furnace chart, McGarry and Madsen Home Inspection
On nine-digit all-number serials from the 1980s the first two digits are the year and the next two are the month.
850304091 reads as March 1985.
Two sources agree Building Intelligence Center, PickHVAC
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)
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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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