A furnace that keeps failing is telling you something
Replacement usually starts with a pattern, not one breakdown. The same part fails twice in a season. The blower gets louder and the far rooms stay cold. Ignition takes several tries. Parts for the model are getting hard to find. In the Shetland Street houses north of the Grand River, many furnaces are still standard-efficiency units vented into the chimney, and these are often the ones that come up for replacement.
None of this means the furnace has to go. A technician looks at the whole system and tells you whether a repair is worth making. If it is, see furnace repair. If it is not, you get a written price for the replacement and the reasons behind it.
A cracked heat exchanger ends the discussion
The heat exchanger keeps the flame and its exhaust separate from the air blown through your house. When it cracks, combustion gases, including carbon monoxide, can get into that air. A furnace with a cracked heat exchanger should not be left running. On an older furnace, this is the point where replacement is the practical answer.
Check your carbon monoxide alarms at the same time. The Ontario Fire Code requires a working CO alarm next to each sleeping area in a home with a fuel-burning appliance, a fireplace or an attached garage. A furnace change is a good moment to test them and replace any that are past their date.
Each kind of Caledonia house brings its own replacement job
The oldest homes around Edinburgh Square and Caithness Street were built for wood or coal and converted later, often to a boiler, a gravity system or add-on forced air. Ductwork, where it exists, is usually cramped and retrofitted. Old wrap on pipes and ducts can contain asbestos, which has to be dealt with before anyone disturbs it. If the house heats with a boiler and radiators, a furnace is not always the right swap, and the chimney will likely need a liner once the equipment changes.
The Shetland Street area grew enough to need Caledonia Centennial Public School, and its houses typically came with standard-efficiency gas furnaces vented into a chimney. Moving to high efficiency changes the venting, and the original ducts are often too small for central air. If the ducts need work anyway, price a heat pump or hybrid system alongside the furnace.
Homes in Avalon, the newer development, already have high-efficiency condensing furnaces with plastic side-wall venting. Replacement there is uncommon. A shutdown is more often a frozen vent or a blocked condensate drain, which is a repair, not a new furnace.
Sizing starts with the house and its ducts
The label on the old furnace is not a sizing method. The old unit may have been oversized from the start, and windows, insulation and additions have changed the house since. The technician looks at the house itself: its size, insulation, windows and how air moves through it.
Then the ducts. A new variable-speed furnace pushed through undersized returns runs loud and wears out early. Where the ducts limit what the house can take, you are told plainly, with the options: a return-air upgrade, a different furnace size, or a different system.
Fuel matters too. Natural gas in Caledonia comes from Enbridge Gas, but parts of Haldimand County are still not on the gas network. A propane furnace is set up differently from a natural gas one, so say which fuel you have when you book. For properties beyond the gas main, a heat pump is worth comparing.
Venting, the chimney and the water heater are checked before the install
A high-efficiency furnace vents through plastic pipe in the side wall, not the chimney. If a gas water heater stays on that chimney alone, the flue is now oversized for it. It can draft poorly and collect condensation, which damages the chimney and can push exhaust back into the basement. The fix is usually a liner sized to the water heater or a change to how the water heater vents. Either way it goes on the written price, not on a later invoice.
Where the side-wall pipes exit matters as well. Intake and exhaust have to clear windows, doors, grade and the snow line. A vent placed too low gets buried in a Caledonia winter and the furnace shuts itself off.
Installations follow the CSA B149.1 Natural Gas and Propane Installation Code, adopted in Ontario under Ontario Regulation 212/01. Work is performed by TSSA-certified gas technicians.
The price is in writing before the old furnace comes out
After the assessment you get a written price covering the furnace, venting, any chimney liner, duct changes and removal of the old unit. You approve it before anything is fitted. On install day the gas is shut off, the old furnace disconnected and removed, and the new one set, piped, vented, wired and drained. The technician starts it, tests combustion and the safety controls, sets up the thermostat and shows you where the filter goes.
Register the new furnace with the manufacturer and keep up annual maintenance, since manufacturer warranties often depend on both. When you are ready, request a quote.