Furnace installation day: what to expect

Furnace only

About 1 dayLonger with venting or duct changes

Furnace with AC, or a heat pump

1 to 2 daysElectrical work can add time

Heat off

Most of the dayAsk about temporary heat

You need to be home

Start and finishFor the plan and the walkthrough

How long does furnace installation take?

A like-for-like gas furnace replacement in a house usually fits in one working day. The crew arrives in the morning and leaves by late afternoon, and your heat is off for most of that time. Adding central air or a heat pump often pushes the job into a second day, mostly for the refrigerant lines, the outdoor unit and the electrical work.

These make a day run longer, and each should be on your quote before install day (prices are the FurnaceQuotes.ca typical ranges for Ontario add-ons, before HST):

• Switching from chimney venting to new plastic venting, or lining the chimney for a water heater left on its own ($300 to $1,500).
• A condensate pump where there is no floor drain close by ($150 to $350).
• Duct changes beyond simple connections ($500 to $3,000+).
• Gas line changes ($300 to $1,200).
• Moving the furnace, tight access or finished ceilings around the ducts.

If any of these come up for the first time on the day, that is a gap in the quote. Our guide to what a furnace quote should include shows where each one belongs, and our questions to ask before signing help you settle them at the estimate.

How to prepare

Most of the preparation is about space, access and heat.

In winter, plan for the house to cool while the heat is off. A well-insulated house cools slowly and an older one faster. Ask the company whether they bring temporary heat, keep a portable electric heater ready if a baby, an older person or anyone unwell is at home, and close blinds and interior doors to slow the heat loss. If you work from home, expect noise and open doors.

Hour by hour: how the day usually runs

Every crew works a little differently, but a straightforward furnace replacement follows much the same order. The times are an example for an 8:00 a.m. start.

1. 1

   8:00 a.m. Arrival and protection

   The lead installer confirms the equipment and venting route on the quote with you, then lays floor runners and drop cloths.

2. 2

   8:30 a.m. Gas and power off

   The gas valve to the furnace is closed and its power switched off. The water heater usually keeps running.

3. 3

   8:45 a.m. Old furnace out

   Venting, gas, wiring and ducts are disconnected and the old unit goes to the truck. If it shared a chimney with a gas water heater, the crew checks the water heater still vents safely alone.

4. 4

   10:00 a.m. New furnace set in place

   Level, on a pad or platform, with room for the filter and service access.

5. 5

   10:30 a.m. Venting and condensate

   Plastic vent pipe, sloped and supported, usually exits a side wall, with the ends clear of windows, doors, the gas meter and the snow line. A drain line or pump carries condensate to a floor drain.

6. 6

   11:30 a.m. Duct transitions

   Sheet metal transitions join the furnace to the existing ducts, with sealed joints. Any AC coil sits on top.

7. 7

   12:30 p.m. Gas connection and leak test

   The gas line is connected, usually with a shut-off valve and sediment trap, and every joint is leak tested.

8. 8

   1:15 p.m. Electrical

   Power switch, thermostat wire, and any condensate pump, humidifier or AC controls.

9. 9

   2:00 p.m. Startup and combustion checks

   The technician checks gas pressure, temperature rise against the rating plate, the exhaust with a combustion analyzer, airflow and safety switches. Ask for a copy of the readings.

10. 10

    3:00 p.m. Thermostat

    Connected and set up for the furnace's stages, with a schedule if you want one.

11. 11

    3:30 p.m. Cleanup

    The old furnace and debris leave with the crew, and the work area is vacuumed.

12. 12

    4:00 p.m. Walkthrough

    The filter, the condensate route, the vents and the thermostat, then the paperwork and the invoice.

Before the crew leaves: a checklist

Take ten minutes before the crew packs up. A question is much easier to sort out while the installer is still in your basement.

Keep everything in one folder with your quote. If you compared quotes with our quote comparison worksheet, print it and add it too: it records what each company promised.

The first few weeks

A new furnace sounds and behaves a little differently from the old one. Most of it is normal.

• A burning smell. Oil and dust on new parts burn off in the first hours of heating. Open a window if it bothers you; it should fade within a day or two. If you smell gas, a rotten-egg smell, leave the house and contact your gas utility's emergency line from outside.
• Longer, quieter runs. Two-stage and modulating furnaces run on low most of the time. Long cycles are how they work.
• New sounds. The inducer fan starts before the burner and you may hear it. Whistling registers or a loud rush of air can mean the blower needs adjusting, so mention it.
• The first filter. Check it after a month. Dust from the installation often loads it quickly.
• The first cold snap. Check the condensate drain or pump when the furnace runs hard, and keep the vent ends outside clear of snow and ice.
• Uneven rooms. Give it a week, then ask about balancing the duct dampers if one room stays cold.

If the company offers a follow-up visit, take it. If anything on the quote was not done, raise it in writing now, not next winter.

When air conditioning or a heat pump goes in too

Central air or a heat pump adds an outdoor unit, refrigerant lines and electrical work, and usually a second day.

• The outdoor unit. An air conditioner sits on a pad. A heat pump usually sits higher, on a stand or wall brackets, clear of snow and with room for defrost water to drain.
• Coil, lines and vacuum. A coil goes on the furnace and copper lines run outside. The lines are pressure tested, usually with nitrogen, then pulled into a deep vacuum before the refrigerant is released. Ask how this was checked.
• Electrical. A new 240-volt circuit and an outdoor disconnect switch. Some homes need more panel capacity (heat pump electrical work $500 to $2,500, a panel upgrade $2,000 to $4,500, before HST). In Ontario this work falls under the Electrical Safety Authority (ESA), so ask who files the notification.
• Controls. With a heat pump and gas furnace backup (dual fuel), the thermostat or control decides when to switch from the heat pump to gas. Ask what temperature it is set to and why.

For typical prices and what those quotes should cover, see central air conditioner quotes and heat pump quotes, or furnace replacement quotes if the furnace is the only job. For more on reading and comparing quotes, see the Quote Guide.