Bosch (heat pumps and geothermal) heating and cooling equipment carry the build date inside the serial number. We know one serial format for this brand; the decoder tries each one and shows every reading that fits.
Skip the first four characters. The next three are Bosch's date code: the first is the last digit of the year and the other two are a month code that changed in 2014 and 2020. Bosch publishes the table.
3540-112-000001-T111M01973 reads as December 2011.
Two sources agree Bosch Home Comfort serial number guide, Building Intelligence Center
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
A ductless mini-split is a heat pump, so plan on 10 to 15 years, with 20 possible for a lightly used unit that is cleaned regularly.
How long does a ductless mini-split last? · Should I replace my air conditioner? · same range as air-source heat pumps
The indoor unit of a geothermal system is expected to last 20 to 25 years. The buried ground loop is expected to last 50 years or more.
How long does a geothermal heat pump last? · Should I replace my furnace? · to be sourced in Stage 3
Should I replace my furnace? · Should I replace my air conditioner?
Mitsubishi Electric · LG · Fujitsu · Gree · ClimateMaster · WaterFurnace
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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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