BC

Boreal Comfort series

24

24 kW of propane input

M

Mid efficiency, 78% AFUE

E

Made in 1992

At 78% AFUE, about 24 × 0.78 ≈ 18.7 kW of that propane became heat in the house. The rest went up the flue.

This furnace is 34 years old. Most furnaces last 15 to 25 years. On most real furnaces the year hides in the serial number; this one was worn off, so you went through the model number.

126 W/°C × (21 − (−25)) °C = 5,796 W ≈ 5.8 kW

Air sealing: 7.0 → 4.2 ACH50; peak heat loss: 6.4 → 5.8 kW. These are scenario values. Equipment sizing also needs cold-weather capacity, defrost and backup-heat checks.

The old furnace put out 18.7 kW, about 3 times what this house needs on the coldest night.

Why the camera works: the blower door pulls the house to −50 Pa, so every gap draws in outside air. On a winter day that air shows up as cold streaks.

4,110 kg (furnace) − 340 kg (heat pump) ≈ 3,770 kg
Energy bought: 19,400 → 4,870 kWh, 14,530 kWh less

The loop moves heat instead of making it. Outdoors, the cold refrigerant is colder than −2 °C air, so it soaks up heat and boils. The compressor squeezes that gas until it's hotter than the house, the indoor coil hands the heat over, and the expansion valve drops the pressure to start again.

That's why almost two-thirds of the heat comes free from outside. On Ontario's mostly nuclear and hydro grid, each kWh carries about 70 g of CO₂e, against roughly 210 g for a kWh of propane.

3.8 tonnes a year is about 80% of what a typical car emits in a year. Switching the water heater and stove off propane too saves about another 0.5 t.

Illustrative annual operating savings for the full retrofit package: air sealing, heat pump, electric water heater and stove, and propane tank removal. Installation and financing costs are excluded.

$2,805 (propane year) − $920 (heat pump year) = $1,885

Heating alone saves about $1,600: heat from propane costs about 14 ¢ per kWh, from the programmed heat pump about 3 ¢ after the Ontario Electricity Rebate. Picking up the tank and retiring the old A/C add the rest. Left unprogrammed, the heat pump would cost $166 more a year.

Furnace dated, scenario energy calculated, house sealed, loads programmed, heat pump running, savings explained. The family is warm again.