What is likely due on your system, and what is not

A heating and cooling system is a dozen components on a dozen clocks, and they rarely reach the end together. Tell it when the house was built and what has already been done, and it will show you where each part sits.

This is not a diagnosis and not a prediction. It compares ages against service-life ranges widely used in the trade. Equipment can fail at eight years or last past twenty. Runtime, airflow and installation quality matter more than the calendar. Use it to decide what to look at, not what to buy.

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System age check

When was the house built? What heats and cools it now?

What has already been replaced?

Leave a row as Original if it has never been done, or if it was done before you owned the house and you have no record of it.

Main heating & cooling equipment Outdoor unit: coil, capacitor, contactor Ductwork and its insulation Thermostat and controls Refrigerant line set Condensate drain and safety switch Heat exchanger (gas furnaces) (if applicable) Backup / auxiliary heat (heat pumps) (if applicable) Water heater

A hundred days of load find the weakest link. It is almost never the box out in the yard. Which is why the ducts and the airflow are worth knowing the age of, not just the box.

Tap to enlarge

1 Thermostat. Where the season’s mileage actually accumulates.
2 Return and filter. Undersized in half the retrofits, and the reason the far room never cools.
3 Air handler and furnace. The part of the system Alabama barely uses, and almost never checks.
4 Coil and condensate drain. Liters of Gulf moisture a day, all leaving through one narrow line.
5 Attic ducts. Conditioned air, routed through the hottest space in the building.
6 Outdoor unit. Where a Gulf-coast August decides which capacitors see another summer.

Why the age of the equipment is not the age of the system

A replacement usually swaps the equipment and keeps everything around it: the ducts, the line set, sometimes the thermostat. The box resets; the loop does not. That is why the tool asks about the ductwork and the lines separately, and why the honest answer for many houses is that nobody knows, because the record of past work left with a previous owner.

The same applies in reverse: a house can carry a young, healthy system strangled by sixty-year-old ducts, and the symptoms (weak rooms, high bills, short cycles) will read as equipment failure to everyone who does not measure. If a report blames the box without ever mentioning the loop, the useful follow-up question is what the static pressure was.

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